Dissertations / Theses: 'Stimulus responsive hydrogel'

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Salehpour, Somaieh. "Synthesis of Stimuli-responsive Hydrogels from Glycerol." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/20584.

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Due to an increased environmental awareness and thus, concerns over the use of fossil-based monomer for polymer production, there is an ongoing effort to find alternatives to non-renewable traditional monomers. This has ushered in the rapid growth in the development of bio-based materials such as green monomers and biodegradable polymers from vegetable and animal resources. Glycerol, as a renewable bio-based monomer, is an interesting candidate for sustainable polymer production. Glycerol is a renewable material that is a by-product of the transesterification of vegetable oils to biodiesel. Utilization of the excess glycerol derived from the growing biodiesel industry is important to oleochemical industries. The main objective of this thesis was to produce high molecular weight polyglycerol from glycerol and synthesize stimuli-responsive polyglycerol hydrogels. The work began with an investigation of the step-growth polymerization of glycerol to relatively high molecular weight polyglycerol using several catalysts. The catalytic reaction mechanisms were compared and the polymer products were fully analyzed. High molecular weight partially branched polyglycerol with multimodal molecular weight distributions was obtained. The polymerization of glycerol proceeded fastest with sulphuric acid as catalyst as indicated by the highest observed conversion of monomer along with the highest molecular weights. Theoretical models were used to predict the gel point and to calculate monomer functionality. High molecular weight polyglycerol was used to synthesize novel stimuli-responsive hydrogels. Real-time monitoring of step-growth polymerization of glycerol was investigated using in-line and off-line Attenuated Total Reflectance/Fourier Transform infrared (ATR-FTIR) technique.

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Kim, Jongseong. "Stimuli-Responsive Hydrogel Microlenses." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14496.

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This dissertation is aimed towards using stimuli-responsive pNIPAm-co-AAc microgels synthesized via free-radical precipitation polymerization to prepare stimuli-responsive hydrogel microlenses. Chapter 1 gives a detailed background of hydrogels, and their applications using responsive hydrogels. Chapter 2 describes the use of colloidal hydrogel microparticles as microlens elements and the fabrication method to form the hydrogel microlens arrays via Coulombic interactions. Chapter 3 shows the demonstration of tunable microlenses prepared by the method used in Chapter 2. In this chapter the microlenses are subjected to various pH and temperature in aqueous solutions. Chapter 4 describes that the microlens arrays constructed on Au nanoparticle-functionalized glass substrates by self-assembly display dramatic changes in lensing power in response to an impingent frequency-doubled Nd:YAG laser. The microlens photoswitching is highly reversible, with sub-millisecond lens switching times. Chapter 5 describes the development of bioresponsive hydrogel microlenses as a new protein detection technology. The microlens method is shown to be very specific for the target protein, with no detectable interference from nonspecific protein binding. Chapter 6 describes the use of bioresponsive hydrogel microlenses as a label-free biosensing scaffolding. These microstructures simultaneously act as the biosensors scaffolding/immobilization architecture, transducer, amplifier, and also allow for broad tunability of the analyte concentration to which the microlens is sensitive.

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Kulawardana, Erandimala Udamini. "Stimuli-Responsive Polymers." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1280669888.

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Binti, Adrus Nadia [Verfasser], Mathias [Akademischer Betreuer] Ulbricht, and Christian [Akademischer Betreuer] Mayer. "Stimuli-Responsive Hydrogels and Hydrogel Pore-Filled Composite Membranes / Nadia Adrus. Gutachter: Christian Mayer. Betreuer: Mathias Ulbricht." Duisburg, 2012. http://d-nb.info/1021899720/34.

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Sterner, Olof. "Swelling and protein adsorption characteristics of stimuli-responsive hydrogel gradients." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-58586.

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In this work, a gradient of interpenetrating polymer networks, consisting of anionic

and cationic polymers, has been investigated with respect to protein resistant

properties and swelling characteristics at different pH and ionic strength

conditions.

The swelling and protein adsorption have been studied using in situ spectroscopic

ellipsometry(SE) and imaging surface plasmon resonance(iSPR) respectively.

It has been shown that, by altering the buffer pH, the region of lowest

protein adsorption on the surface could be moved laterally. The swelling has

similarly been shown to respond to both changes in pH and ionic strength. Additionally,

the arise of surface charge and the polymer swelling in solution, both a

consequence of the ionisation of fixed charges on the polymer, have been indicated

to occur at different buffer pH.

The studied polymer systems show promising properties for future applications

in, for example, the biosensor area, where the surface chemistry can be

tailor-made to work optimally in a given environment.

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Gicquel, Erwan. "Development of stimuli-responsive cellulose nanocrystals hydrogels for smart applications." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI105/document.

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L’originalité de ce projet consiste au développement et à l’étude de nouvelles structures hybrides à base de nanocelluloses et de polymères stimulables. En particulier, c’est le design d’hydrogels aux propriétés thermosensibles qui est visé. Les nanocelluloses - nanoparticules issues de la cellulose - sont de deux types : les nanocristaux de cellulose (CNCs) et les nanofibrilles de cellulose (CNFs) et possèdent des propriétés bien particulières. Cette étude s’est concentrée sur l’élaboration d’hydrogels de CNCs. Plusieurs polymères thermosensibles ont été utilisés pour leur biocompatibilité et leur température de solution critique (LCST) aux abords de la température du corps humain. Ce travail a consisté en (i) la préparation des systèmes sur les principes de la chimie verte, (ii) l’étude rhéologique de ces gels thermosensibles et (iii) l’élaboration d’applications à forte valeur ajoutée pour ces biomatériaux uniques. A travers l’utilisation de grands équipements (SANS, SAXS), les interactions physico-chimiques CNCs/polymères ont été étudiées. L’utilisation de block copolymères a permis l’obtention de suspension de CNCs aux propriétés rhéologiques spécifiques : de liquide a température ambiante à gel viscoélastique à température du corps. D’un point vue applicatif, les hydrogels ainsi réalisés ont permis le déploiement de systèmes injectables pour le biomédical ainsi que des surfaces thermosensibles.Mots clés : nanocristaux de cellulose, hydrogel, thermosensible, stimulable
This project consists to develop and study new hybrid structures based on nanocelluloses and stimuli-responsive polymers, in particular, thermo-responsive polymers. Nanocelluloses - nanoparticles extracted from cellulose - exist in two forms: cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs). This study focused on the design of CNCs hydrogels with stimuli-responsive polymers. Several thermo-responsive polymers have been used for their biocompatibility and lower critical solution temperature (LCST) close to body temperature. This work consisted of (i) preparation of systems using the principles of green chemistry, (ii) the rheological study of these thermo-sensitive hydrogels, and (iii) the development of smart applications for these unique biomaterials. Through the use of state of the art technologies (SANS, SAXS), physicochemical interactions between the polymers and CNCs have been studied. The use of block copolymers made it possible to create CNCs-based hydrogels with specific rheological properties: liquid at ambient temperature to viscoelastic gel at body temperature. These hydrogels can be used in the creation of injectable systems for biomedical applications, as well as thermosensitive surfaces.Key-words: Cellulose nanocrystals, hydrogel, thermo-responsive, stimuli-responsive

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Sato, Jun. "Transient Rheology of Stimuli Responsive Hydrogels: Integrating Microrheology and Microfluidics." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-10272006-133420/.

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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007.
Andreas S. Bommarius, Committee Member ; L. Andrew Lyon, Committee Member ; J. Carson Meredith, Committee Member ; William J. Koros, Committee Member ; Victor Breedveld, Committee Chair.

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Matsumoto, Shinji. "Novel Stimuli-Responsive Supramolecular Hydrogels toward Sophisticated Nano-Micro Biomaterials." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/57282.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第13850号
工博第2954号
新制||工||1436(附属図書館)
26066
UT51-2008-C766
京都大学大学院工学研究科合成・生物化学専攻
(主査)教授濵地格, 教授青山安宏, 教授木村俊作
学位規則第4条第1項該当

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Tanaka, Wataru. "Development of stimuli-responsive supramolecular hydrogels relying on self-sorting." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263692.

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Trotter, Johann Louise. "Development of stimuli-responsive hydrogels to combat infection of biomaterials." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728682.

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The development of medical device-associated infections is an increasing burden on modern healthcare. Currently there are no methods fully effective at preventing or eradicating these infections. The aim of this thesis was to develop stimuli-responsive hydrogels as new alternative methods to try and combat such infections, with particular focus placed on catheter-associated urinary tract infections (CAUTIs). Urease-producing bacteria, such as Proteus mirabilis, are prevalent organisms in CAUTIs and cause an increase in pH at the catheter surface. This change in pH was exploited in this thesis wherein a pH- triggered system has been developed and characterised, comprised of a surfactant tethered to a polymeric backbone. An increase in pH was shown to cleave these bonds and accelerate the release of surfactant with 5 times more surfactant released at pH 10 than pH 7 after 28 days. Materials were also shown to demonstrate significant reductions in antimicrobial adherence when challenged with Proteus mirabilis and Staphylococcus aureus. A low-friction coating with an improved dry-out time for intermittent catheters has also been characterised and the effect of retraction speed during the dip coating process on a number of different parameters has been assessed. The highly effective chlorhexidine diacetate has also been incorporated into the coating as a means of enhancing antimicrobial efficacy with up to 5 log reductions in bacterial adherence observed. Lastly, a photolabile crosslinker was developed and incorporated into hydrogels to produce a photoresponsive material. Irradiation of the materials was shown to cleave the crosslinker, increasing porosity and subsequently swelling and drug release. This thesis therefore provides a range of novel materials that have been shown to display antimicrobial or anti-adherent properties and therefore have demonstrated a potential applicability to prevent medical device infections.

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Maslovskis, Antons. "Responsive hydrogels using self-assembling polymer-peptide conjugates." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/responsive-hydrogels-using-selfassembling-polymerpeptide-conjugates(ca090402-aaa1-4729-8d0d-76dd07401521).html.

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Stimuli-responsive polymers and self-assembling peptides represent two classes of materials with interesting properties and great potential to be used as biomaterials. The conjugation of polymer with peptide offers a way to combine the controlled chemical, mechanical, and thermal properties of polymer with the functionality of designed bioactive group. Pure hybrid materials with the characteristics of individual components or systems containing hybrid materials became attractive for applications in drug delivery and tissue engineering. This work focused on systems where the thermo-responsive properties of a polymer were combined with the gelling properties of two different ionic-complementary peptides via conjugation. The prototypical thermo-responsive polymer poly(N-isopropylacrylamide) (PNIPAAm) was chosen due to its lower critical solution temperature (LCST) ~32°C being close to body temperature. Ionic-complementary oligo-peptides, containing the alternating hydrophobic/hydrophilic and charged/uncharged amino acids, phenylalanine (F), glutamic acid (E) and lysine (K), were selected as they are known to form β-sheet rich fibrillar networks at low concentrations. Two peptide sequences with different charge distribution were chosen: FEFEFKFK and FEFKFEFK which form self-supporting gels at ~17 and 10 mg ml-1 respectively. Polymer-peptide conjugates were used to confer self-assembling and thermo-responsive behaviour to the system.Thermo-responsive PNIPAAm-rich hydrogels were obtained by targeting different degrees of functionalisation of PNIPAAm with the self-assembling peptides. Two series of such systems were prepared by using either a thiol-modified FEFEFKFK or a thiol-modified FEFKFEFK peptide as the chain-transfer agent in the free radical polymerisation of NIPAAm. The resulting polymer/conjugate mixtures were studied by proton nuclear magnetic resonance (1H NMR). The polymer/conjugate ratios were calculated and showed that the conjugate fraction in the mixtures increased with increasing concentration of peptide used for the polymerisation. Static light scattering (SLS) and viscometry showed the aggregation of the polymer/conjugate mixtures presumably due to the presence of peptide. The values from gel permeation chromatography (GPC), which were mostly attributed to the unconjugated polymers, were higher than those obtained from 1H NMR and centrifugation for the conjugates. The polymer/conjugate mixtures formed self-supporting gels where the critical gelation concentration decreased with increasing conjugate content. Oscillatory rheology experiments confirmed gels had formed and revealed that their elastic modulus, G' varied from ~ 10 to 400 Pa depending on the sample. TEM and AFM studies proved the formation of β-sheet fibres of ~ 4.5 ± 1.5 nm in diameter. The PNIPAAm-rich hydrogels were also characterised by micro DSC to reveal their thermo-responsiveness and phase separation and showed the LCST at ~ 30°C. The results of the study showed that varying the peptide sequence did not have an effect on thermal, mechanical or morphological properties of the hydrogels. By exploiting the self-assembly of the ionic-complementary peptides, it was possible to create PNIPAAm-rich, thermo-responsive hydrogels with controllable properties.Further in the study pure PNIPAAm-FEFEFKFK conjugate was incorporated into the FEFEFKFK peptide matrix to create peptide-rich thermo-responsive composite gels. Two series of the composite gels were prepared by varying separately the peptide matrix and polymer-peptide conjugate concentration. Micro DSC measurements revealed an endothermic peak at ~ 30ºC characteristic of the LCST of PNIPAAm. Oscillatory rheology studies showed that the composite gels became stronger with increasing conjugate concentration (G' ~ 20 - 200 Pa). Network morphology was studied by SANS. Using contrast variation and contrast matching techniques it was possible to distinguish between the peptide fibres and the PNIPAAm chains. Below and above the LCST the scattering curves showed a q-1 behaviour which is typical of rod-like objects. TEM and AFM also proved the formation of fibres of ~4.0 ± 0.8 nm and ~4.5 ± 1 nm respectively. AFM studies showed that the fibres of the composite gels were decorated with polymer chains. The thermo-responsiveness and the gelation properties of these conjugate-based scaffolds have potential for use as drug delivery vehicles or tissue engineering scaffolds.

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Hippler, Marc [Verfasser], and M. [Akademischer Betreuer] Wegener. "3D Laser Lithography of Stimuli-Responsive Hydrogels / Marc Hippler ; Betreuer: M. Wegener." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1222109484/34.

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Way, Amanda E. "Stimuli-Responsive Nanofiber Composite Materials: From Functionalized Cellulose Nanocrystals to Guanosine Hydrogels." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1390388160.

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Matzelle, Thomas. "Stimuli responsive hydrogels :studies of tribology and rheology using scanning force microscopy." Doctoral thesis, Universite Libre de Bruxelles, 2003. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211234.

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Bottari, Giovanni. "Influencing rotational and translational motion in stimuli-responsive hydrogen-bonded [2]rotaxanes." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/12392.

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The controlled translocation of submolecular units is seen as an important requirement for the future development of “machines” which function through mechanical motion at the molecular level. Mechanically-interlocked molecules, i.e. catenanes and rotaxanes, are ideal candidates for application as components for molecular devices due to the inherent restrictions in the degrees of freedom presented in their architectures. Hydrogen bond-directed assembly offers powerful strategies for the synthesis of such structures on a scale where practical applications become a realistic area for study. This Thesis focuses on (i) the use of hydrogen bonding interactions in the synthesis of structurally different fumaramide template-containing [2]rotaxanes, (ii) the control of the rotational and translational motion in stimuli-responsive [2]rotaxanes and (iii) the control of a physical property, such as elliptical polarization, in a stimuli-responsive two-station [2]rotaxane. The stimuli required to promote the submolecular motion are light and heat.

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Hachet, Emilie. "Systèmes biocompatibles et biodégradables par modification chimique contrôlée de polysaccharides pour le traitement de patients diabétiques." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENV083.

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Ce travail de thèse s'inscrit dans un domaine de recherche actuellement en pleine expansion, celui des nanomatériaux stimulables. Il vise à concevoir de nouveaux matériaux biocompatibles et biodégradables par modification chimique contrôlée de polysaccharides pour le traitement de patients diabétiques. Le diabète est un problème de santé publique majeur qui affecte environ 250 millions de personnes dans le monde actuellement contre 30 millions il y a 20 ans. Cette maladie se traduit par un taux de glucose anormalement élevé dans le sang dû à un manque d'insuline. Cette protéine est habituellement injectée de manière sous-cutanée, 2 à 4 fois par jour. Les hydrogels/nanogels visés dans ce travail doivent donc être capables de libérer l'insuline en fonction du taux de glucose dans le sang. Ce projet comporte plusieurs volets : (i) la synthèse contrôlée de polysaccharides porteurs de groupements permettant la réticulation des polymères ainsi que des molécules sensibles au glucose , (ii) la synthèse et la caractérisation d'hydrogels et nanogels (en utilisant des liposomes comme nanoréacteurs)
This PhD thesis belongs to the area of stimuli-responsive materials, which have attracted a growing interest since several years. Its aim is to design biocompatible and biodegradable stimuli-responsive nanogels obtained from chemically modified polysaccharides to treat diabetic patients. These systems may be used to release insulin in a self-regulated manner. This common disorder of blood glucose regulation due to a lack of insulin is a major public health problem affecting about 250 millions of people in the world today, as compared to 30 millions twenty years ago. Patients diagnosed with insulin-dependent diabetes must take insulin by injecting themselves with a needle at least twice a day. The nanogels targeted in this work are thus expected to release insulin as a function of blood glucose concentration.This project will thus consist in the controlled synthesis of polysaccharides bearing cross-linkable groups and a sugar sensor. These biopolymers will be then used to prepare hydrogels and nanogels (using liposomes as nanoreactors)

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Ali, Wael [Verfasser], and Jochen S. [Akademischer Betreuer] Gutmann. "Brackish water desalination via stimuli-responsive polymeric hydrogels / Wael Ali ; Betreuer: Jochen S. Gutmann." Duisburg, 2019. http://d-nb.info/1200352890/34.

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Karasinski, Michael A. "Manufacturing Microfluidic Flow Focusing Devices For Stimuli Responsive Alginate Microsphere Generation And Cell Encapsulation." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/756.

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In this paper a novel stimuli responsive hydrogel material, methacrylated sodium alginate beta-cyclodextrin (Alg-MA-β-CD), was used in combination with a microfluidic device to create microspheres. Currently there is no reliable method for fabricating homogeneous stimuli-responsive microspheres, in-house microfluidic devices are not reliable in manufacture quality or long-term use. Alginate hydrogels have many attractive characteristics for bioengineering applications and are commonly used to mimic the features and properties of the extracellular matrix (ECM). Human mesenchymal stem cells (hMSCs) are of top interest to tissue engineers. hMSCs are widely available and can be harvested and cultured directly out of human bone marrow. hMSCs have the ability to differentiate into osteoblasts, adipocytes, chondrocytes, muscle cells, and stromal fibroblasts depending on mechanical signals transmitted through surrounding ECM. The biomechanical properties of alginate based stimuli-responsive hydrogels can be tuned to match those of different types of tissues. When trying to transport and control the differentiation of hMSCs into generating new tissues or regenerating damaged tissues, it is highly beneficial to encapsulate the cells inside a microsphere made from these hydrogels. The proposed research objectives are: 1) To optimize fabrication techniques and create functional microfluidic devices; 2) Analyze the effects of flow parameters on microsphere production; and 3) Encapsulate viable hMSCs inside multi-stimuli responsive alginate microspheres using the fabricated microfluidic devices (MFDs). In this study, photolithography microfabrication methods were used to create flow-focusing style MFDs. The hydrogel materials were characterized via rheological methods. Syringe pumps controlled flow rates of fluids through the devices. Active droplets formation was monitored through a camera attached to an inverted microscope, where images were analyzed. Microsphere production was analyzed optically and characterized. Alg-MA-β-CD polymer solutions containing hMSCs were encapsulated, and a live/dead florescence assay was preformed to verify cell viability. Using a modified fabrication process it was possible to manufacture Alg-MA-β-CD microspheres and encapsulate and maintain viable hMSCs inside.

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Eggers, Katharina [Verfasser]. "Polymeranaloge Reaktionen an Guar zur Herstellung von stimuli-responsiven Hydrogelen / Katharina Eggers." München : Verlag Dr. Hut, 2015. http://d-nb.info/1070123846/34.

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Cho, Jae Kyu. "The dynamics and phase behavior of suspensions of stimuli-responsive colloids." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31682.

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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Victor Breedveld; Committee Member: Eric W. Weeks; Committee Member: Hang Lu; Committee Member: J. Carson Meredith; Committee Member: L. Andrew Lyon. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Viswanathan, Kalpana. "Synthesis and Characterization of Novel Polymers for Functional and Stimuli Responsive Silicon Surfaces." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27052.

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The synthesis of a variety of novel functionalized polymers using living polymerization techniques to achieve functional and stimuli responsive coatings on silica surfaces are described. Since microscopic features on a surface influence the overall wetting properties of the surface, a systematic investigation of the influence of polymer architecture on the microscopic characteristics of the modified surfaces was studied using silane-functionalized linear and novel star-branched polystyrene (PS). Star-branched modifiers provide functional and relatively well-defined model systems for probing surface properties compared to ill-defined highly branched systems and synthetically challenging dendrimers. Using these simple star-shaped macromolecules it was shown that the topographies of the polymer-modified surfaces were indeed influenced by the polymer architecture. A model explaining the observed surface features was proposed. A living polymerization strategy was also used to synthesize centrally functionalized amphiphilic triblock copolymers. The amphiphilic copolymers exhibited stimuli responsive changes in surface hydrophobicity. In spite of multiple solvent exposures, the copolymer films remained stable on the surface indicating that the observed changes in surface properties were due to selective solvent induced reversible rearrangement of the copolymer blocks. The chemical composition of the copolymers was tailored in order to tune the response time of the surface anchored polymer chains. Thus, the polymer coatings were used to reversibly change the surface polarities in an on-demand fashion and could find possible applications as smart adhesives, sensors and reusable membrane devices. In contrast to the afore-mentioned covalent modification approach, which often leads to permanent modification of surfaces, renewable surfaces exhibiting â universalâ adhesion properties were also obtained through non-covalent modification. By employing hydrogen bonding interactions between DNA bases, surfaces functionalized with adenine groups were found to reversibly associate with thymine-functionalized polymers. This study describing the solvato-reversible polymer coating was the first demonstration on silica surfaces. A systematic investigation of the influence of surface concentration of the multiple hydrogen bonding groups and their structure on the extent of polymer recognition by the modified surfaces is also discussed.
Ph. D.

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Pini, Cesare [Verfasser], Andreas [Gutachter] Richter, and Ginaurelio [Gutachter] Cuniberti. "Microfluidic Systems based on Chemical Volume-Phase-Transition Stimuli-Responsive Hydrogels / Cesare Pini ; Gutachter: Andreas Richter, Ginaurelio Cuniberti." Dresden : Technische Universität Dresden, 2019. http://d-nb.info/1226897045/34.

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Voigt, Andreas, Uwe Marschner, and Andreas Richter. "Multiphysics equivalent circuit of a thermally controlled hydrogel microvalve." Sage, 2017. https://tud.qucosa.de/id/qucosa%3A35628.

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Temperature-responsive hydrogels are polymer particles whose equilibrium size depends on the temperature of the water they are immersed in. Here we present an equivalent circuit model of a temperature-controlled microvalve based on hydrogel particles. The resulting network model consists of three physical subsystems. The thermal subsystem considers the heat capacities and thermal resistances of the layers of the valve and the coupling to the ambient environment. The polymeric subsystem describes the relaxation of the hydrogel particles to the temperature-dependent equilibrium size. The fluidic subsystem consists of the supply channel and a chamber whose cross section varies according to the size of the hydrogel particles. All subsystems are described and coupled within one single circuit. Thus the transient behavior of the valve can be calculated using a circuit simulator. Simulation results for a setup are presented and compared with experiments.

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Dyakonova, Margarita A. Verfasser], Christine M. [Akademischer Betreuer] Papadakis, and Hendrik [Akademischer Betreuer] [Dietz. "Stimuli-responsive reversible hydrogels from polyampholytes / Margarita A. Dyakonova. Betreuer: Christine M. Papadakis. Gutachter: Christine M. Papadakis ; Hendrik Dietz." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1100159266/34.

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Bessi, Matteo. "Development of new highly conjugated molecules and their application in the field of renewable energy and biomaterials." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF056/document.

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Ces dernières années, les matériaux fonctionnels hybrides ont commencé à être employés pour des applications de la haute technologie, allant des senseurs bio/médicaux, à la production d’énergie renouvelable. Pour cette raison, ils sont devenus le centre de plusieurs études dans le domaine des sciences des matériaux. Simultanément, des molécules conjuguées ont été examinée intensément à cause de leurs propriétés venant de leurs longs systèmes π, allant de la possibilité de conduire l’électricité, à leur capacité d’absorber la lumière dans une grande fenêtre spectrale. Le travail de cette thèse se concentre sur l’introduction de tels systèmes dans deux sortes de matériaux hybrides, les dispositifs photovoltaïques pour la production d’électricité (en particuliers les cellules solaires à pigment photosensible) et de carburants alternatifs (hydrogène), et pour les hydrogels biocompatibles sensibles aux stimuli (capables de conduire l’électricité et de réagir sous irradiation), et sur l’étude de leur influence sur les caractéristiques du matériau final
In recent years hybrid functional materials began to be employed in a series of technologically advanced applications spanning from bio/medical sensors, to renewable energy generation. For this reason, they became the focus of several studies in the field of materials science. At the same time, conjugated molecules have also been intensively investigated, due to the properties arising by the presence of long π-conjugated systems, from the possibility to conduct electricity to the ability to absorb light in a wide range of wavelengths. This PhD work focused on the introduction of such systems in two different kinds of hybrid materials, namely photovoltaic devices for the production of electricity (in particular Dye Sensitzed Solar Cells) and alternative fuels (hydrogen), and biocompatible stimuli-responsive hydrogels (capable to conduct electricity and to react upon irradiation), and on the study of their influence on the characteristics of the final material

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Tirado, Viloria Patricia Carolina. "New saloplastic biomaterials based on ultracentrifuged polyelectrolyte complexes." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAF034.

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Ce travail avait pour but de développer un nouveau type de matériaux basés sur des complexes polyelectrolytes. Ces matériaux ont été obtenus par l’ultracentrifugation des complexes soit d’origine naturelle ou soit d’origine synthétique. Le système de polyélectrolytes ainsi que les conditions dans lesquelles ces matériaux peuvent être obtenus, suivi par le choix du système optimal pour des études complémentaires ont été décrits. PAA / PAH CoPECs a été choisi comme systèmes modèles de synthèse et ses propriétés physico chimiques (composition, structure et les propriétés mécaniques) ont été décrits ici en détails. Nous avons montré que les propriétés de la composition, la structure et mécanique de le PAA/PAH CoPECs peut être contrôlée en modifiant les conditions d’assemblage (pH, concentration des polyélectrolytes, [NaCl], la vitesse et la commande de l’addition). Également, les conditions environnementales ([NaCl] et pH) ont également été utilisés pour contrôler la taille des pores et porosité des PAA/PAH CoPECs . Enfin, leur capacité à servir de support pour l’immobilisation d’enzymes a également été étudiée. Nous avons optimise les conditions d’assemblage afin de maintenir le maximum quantité de l’enzyme dans le complexe. Nous avons également démontré que CoPECs fournit la stabilisation à long terme, ainsi que la protection de l’enzyme à des températures élevées. Ainsi, PAA / PAH CoPECs sont des candidats potentiels pour être utilisé comme des supports pour l’ingénierie tissulaire et pour l’immobilisation d’enzymes
This work was aimed to the develop of a new kind of materials of polyelectrolytes complexes. These materials were obtained by the ultracentrifugation of complexes either of natural or synthetic origin. The polyelectrolytes systems as well as the conditions under which these materials could be obtained, followed by the selection of the optimal system to further studies was described. PAA/PAH CoPECs was chosen as synthetic model systems and its physiochemical properties (composition, structure and mechanical properties) were here deeply described. We demonstrated that the composition, structure and mechanical properties can be controlled by changing the assembly conditions (pH, concentration of the polyelectrolytes, [NaCl], speed and order of addition). Moreover, the environmental conditions ([NaCl] and pH) were also used to control the porosity and pores size of the PAA/PAH CoPECs. Finally their ability to serve as scaffold for enzyme immobilization was also studied. We optimized the assembly conditions to keep the maximum of the activity. We also demonstrated that the CoPECs structure provides the stabilization in long term as well as the protection of the enzyme from high temperature. Thus, PAA/PAH CoPECs is a potential and suitable candidates as scaffold for tissue engineering and for the immobilization of enzymes

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Votte, Guillaume. "Synthèse de cristaux photoniques modulables à partir de films minces d’hydrogel stimulables." Electronic Thesis or Diss., Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLS010.

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La recherche dans le domaine des cristaux photoniques synthétiques progresse à grande vitesse. En parallèle, les progrès réalisés dans le domaine de la matière molle et des polymères permettent également des avancées considérables pour des dispositifs stimulables. Dans ces travaux de thèse, nous avons développé une plateforme permettant désynthétiser des nano- et microstructures d'hydrogel stimulables stables et à grandes amplitudes de déformation. Pour ce faire, nous avons utilisé la méthode CLAG (Cross-LinkingAnd Grafting) qui consiste en la réticulation et le greffage simultanés de chaînes de polymère sur le substrat. Nous avons exploité cette plateforme pour mettre au point des miroirs de Bragg stimulables à grande amplitude de décalage spectral, avec des multicouches alternéesd’hydrogels et des couches d’or ou d’oxyde de titane Nous avons également développé des cristaux photoniques bidimensionnels en utilisant des masques photolithographiques. De plus, l’hyperthermie plasmonique ou magnétique est envisagée pour induire la transition des films d’hydrogel. Enfin, nous avons montré que la plateforme d’hydrogels permet également de coupler la température avec d’autres stimuli: chimiques, mécaniques
Research in the field of synthetic photonic crystals has been advancing at high speed. In thedevelopment of this field, additional performances in terms of modularity and switchabilityusing soft matter and polymers provide unprecedented enhanced devices. In this thesis, wedeveloped a platform of stimuli-responsive nano- and microstructured polymer hydrogelsthat are surface-grafted to ensure chemical stability regardless of environmental change.This strategy is based on CLAG chemistry which consists in simultaneous Cross-Linking AndGrafting of polymer chains on the substrate. This platform is exploited to fabricate stimulableBragg mirrors with large amplitude of spectral shift. We also developed a strategy allowingus to design two-dimensional photonic cristals by using photolithographic masks. Finally, wedemonstrated that the hydrogel platform allows the coupling of temperature with otherstimuli: chemical, mechanical, light and electromagnetic field for plasmonic and magnetichyperthermia

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Giammanco, Giuseppe E. "Photochemistry of Fe(III)-carboxylates in polysaccharide-based materials with tunable mechanical properties." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1478602282499732.

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Li, Haidong. "Electrogenerated chemiluminescence : from materials to sensing applications." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0560/document.

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Le phénomène d’électro chimiluminescence (ECL), également appelé chimiluminescence électrogénérée, consiste en la génération de l’état excité d’un émetteur suite à des réactions de transfert d’électrons se produisant initialement à la surface de l’électrode. L’état excité ainsi produit retourne à l’état fondamental en émettant de la lumière. Les réactions ECL se classent principalement en 2 grandes voies mécanistiques: les réactions d’annihilation et les réactions impliquant un co-réactif sacrificiel. Cette dernière voie a conduit à de très nombreuses applications en chimie analytique. Dans ce manuscrit, j’ai présenté mes travaux de thèse qui ont suivis 3 directions complémentaires depuis l’échelle moléculaire jusqu’à l’échelle macroscopique: la recherche de nouveaux luminophores ECL, l’étude de films d’hydrogels stimulables et le développement de nouvelles applications analytiques de l’ECL.Dans une première partie, j’ai étudié les propriétés ECL de 3 types de luminophores organiques. Ces composés ont montré des caractéristiques électrochimiques et ECL remarquables. L’efficacité ECL de ces luminophores organiques peut être modulée enjouant sur leurs structures respectives. Des luminophores de type spirofluorène ont produit une émission ECL très intense et les nanoparticules organiques correspondantes ont pu être utilisées comme nano-émetteurs ECL. L’étude des propriétés électrochimiques, photochimiques et ECL de luminophores cationiques de type triangulène et hélicène a été réalisée et présentée avec un formalisme montrant un «mur» ECL ou une cartographie ECL complète.Dans une seconde partie, la préparation de films d’hydrogels thermo-stimulables à base de poly(N-isopropylacrylamide) ou pNIPAM incorporant des centres redoxRu(bpy)3 a été réalisée sur des électrodes de carbone vitreux (GCE) et aussi sur des fibres de carbone par polymérisation radicalaire induite électrochimiquement. Les études ECL sur les GCEs modifiées ont montré que le facteur principal gouvernant les propriétés ECL est la distance entre les sites Ru(bpy)3. Le dépôt de tels films de pNIPAM-Ru(bpy)3 par électrochimie bipolaire ouvre de nouvelles possibilités pour le développement de micro-objets stimulables hybrides. Dans une dernière partie, comme la chimie analytique constitue un des plus importants attraits de l’ECL, deux applications analytiques sont présentées en utilisant,d’une part, des co-réactifs de type amine modifié par l’acide phénylboronique, et,d’autre part, des faisceaux de fibres optiques recouverts d’or. La réaction de complexation de saccharides par le groupe phénylboronique modifie les propriétés électrochimiques du co-réactif amine en rendant son oxydation à l’électrode inefficace,ce qui provoque la diminution du signal ECL. En changeant la longueur de l’espaceur de ces co-réactifs qui portent deux groupements phénylboroniques, nous avons pu mesurer sélectivement la concentration de D-glucose et de D-fructose. Mon travail a enfin porté sur le développement d’un objet analytique basé sur un faisceau de fibresoptiques doré qui est adressé sans contact par électrochimie bipolaire. L’ECL ainsi générée du système Ru(bpy)32+/TPrA a permis de réaliser un outil activable à distance permettant une mesure déportée via le faisceau. Ce nouvel objet analytique original devrait permettre d’étendre les mesures ECL à des environnements confinés ou dangereux
Electrogenerated chemiluminescence (ECL) involves the energetic electron transfer reactions at the electrode with the generation of excited state of emitter, which then relax to the ground state and emit light. These ECL reactions can be divided into two main pathways: the annihilation and sacrificial co-reactant reactions. The latter has found a lot of applications in analytical chemistry. In this thesis, ECL studies towardt hree complementary directions are presented, ranging from the molecular scale tomacroscopic scale : the research of new ECL luminophores, the study of stimuli-responsive hydrogel films, and the development of new ECL assays.Firstly, I have studied three types of organic dyes for ECL investigations. These organic dyes exhibit interesting electrochemical and ECL properties. ECL efficiencies of the organic dyes can be tuned by the modification of the structures. Spirofluorene dyes show strong ECL emission, and thus its fluorescence organic nanoparticles(FONs) prepared in water were used as ECL nano-emitters. We also established an energetic ECL “wall” representation and then move forward creating ECL “map”upon electrochemical, photoluminescence and ECL studies on cationic triangulenes and cationic helicenes dyes, respectively.Secondly, the preparation of thermo-responsive poly(N-isopropylacrylamide)(pNIPAM) hydrogel films covalently incorporating Ru(bpy)3 redox centers were achieved on glassy carbon electrode (GCE) or carbon fiber by electrochemically induced free radical polymerization. ECL studies on the modified GCEs have provided the main factor (the average distance of Ru(bpy)3 sites) that governs the ECL process, leading to deciphering the enhanced ECL in the films. The deposition of the films on carbon fiber by bipolar electrochemistry (BPE) has opened new route to for the development of smart hybrid micro objects. Finally, analytical application is one of the most important features of ECL. We presented two different ECL assays using either the phenylboronic acid modified amine based co-reactants or gold coated optical fiber bundle. The binding of saccharides with boronic acid modified tertiary amines makes the oxidation of amines group inefficient, which decreases ECL signal response. By changing linker length of a bis-boronic acid amine co-reactant, we are able to determine D-glucose and D-fructose selectively. We also studied the ECL generation of Ru(bpy)32+/TPrA systemon the gold coated optical fiber bundle in a wireless manner by BPE, then transmission and remote detection at the opposite end of the same object. This methodmay extend the applicability of ECL assays in the confined or hazardous environments
电化学发光（ECL）的发生是由于在电极表面通过电子转移反应生成了发光体的激发态跃迁到基态，并伴随着发光。这些电子转移反应可划分为两种主要的途径：正负自由基湮灭反应和共反应物反应。而后者被广泛应用于分析化学领域。在本论文中，我们在电化学发光领域中进行了广泛的研究，具体有三个研究方向：新型电化学发光光团的研究、响应水凝胶膜的制备以及电化学发光分析的研究。首先，我们选择了三种不同类型的有机荧光分子用于电化学发光的研究。这些有机荧光分子展现出许多电化学和电化学发光特性。其中，螺芴荧光分子展现出了非常强的电化学发光。而且用它制备的荧光有机纳米颗粒（FONs）在水相中也可以产生电化学发光。基于对阳离子型三角烯和阳离子型螺烯的电化学、光谱学以及电化学发光的研究，我们分别建立了鉴别电化学发光“墙”和“图谱”。其次，利用自由基电聚合的方法，我们实现了在玻碳电极和碳纤维表面上制备热刺激-响应的聚异丙基丙烯酰胺（p-NIPAM）共价嫁接三联吡啶钌Ru(bpy)3 荧光分子的水凝胶膜。通过对玻碳电极上水凝胶膜的电化学发光的研究，我们发现了控制水凝胶膜中电化学发光的主要因素，从而揭秘了水凝胶膜中电化学发光增强的成因。而且，利用双电极化学（BPE）的方法，我们将此类水凝胶膜的制备应用于碳纤维上，以发展灵敏杂化微米级器件。最后，鉴于化学分析是电化学发光最重要的特征，我们构建两种不同的电化学发光分析体系：一种是基于硼酸化学修饰的三丙胺共反应物；另一种是利用镀金光导纤维。硼酸对糖类的结合弱化了三丙胺的电化学氧化效率，因此影响电化学发光的强度。通过改变双硼酸修饰共混物之间碳链的长度，我们实现了对葡萄糖和果糖的选择性检测。我们还研究了在镀金光导纤维上三联吡啶钌/三丙胺体系的电化学发光。此研究是在双电极体系进行的，镀金光导纤维无需外部接线，镀金部位产生的发光透过光纤传输的光纤的远端，再进行检测，因此达到了电化学发光的远程检测。这一方法可应用于狭窄危险环境中的电化学发光分析。

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Chang, Debby Pei-Shan. "Mechanical and Tribological Study of a Stimulus Responsive Hydrogel, pNIPAAm, and a Mucinous Glycoprotein, Lubricin." Diss., 2009. http://hdl.handle.net/10161/1359.

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Friction is the resistive force that arises when two contacting surfaces move relative to each other. Frictional interactions are important from both engineering and biological perspectives. In this research I focus on the fundamental understanding of friction on polymeric and biological surfaces in aqueous environments. First, I examine the frictional properties of a stimulus-responsive hydrogel, poly-N-isopropylacrylamide (pNIPAAm), to understand how different phase states affect its tribological properties. My measurements indicate that gels in a collapsed conformation at low shear rates, exhibit significantly larger friction than swollen gels. These differences arise from changes in surface roughness, adhesive interactions, and chain entanglements of the gel surfaces associated with the phase transition. Importantly, I show that the changes in friction, triggered by an external stimulus, are reversible.

Second, I examine details of the boundary lubrication mechanism involved in mediating friction and wear in diarthrodial joints. Specifically, I looked at the constituents of the synovial fluid, lubricin and hyaluronic acid (HA) and examined their interactions on model substrates, (1) to determine the effect of surface chemistry on adsorption using surface plasmon resonance (SPR), and (2) to study normal force interactions between these surfaces using colloidal probe microscopy (CPM). I found that lubricin is highly surface-active, adsorbed strongly onto hydrophobic, hydrophilic and also collagen surfaces. Overall, lubricin develops strong repulsive interactions. This behavior is in contrast to that of HA, which does not adsorb appreciably, nor does it develop significant repulsive interactions. I speculate that in mediating interactions at the cartilage surface, an important role of lubricin is one of providing a protective coating on cartilage surfaces that maintains the contacting surfaces in a sterically repulsive state.

Dissertation

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"Mechanical and Tribological Study of a Stimulus Responsive Hydrogel, pNIPAAm, and a Mucinous Glycoprotein, Lubricin." Diss., 2009. http://hdl.handle.net/10161/1359.

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Chan, ARIEL WAN-JU. "CONTROLLED SYNTHESIS OF STIMULI-RESPONSIVE NETWORK ALGINATE." Thesis, 2009. http://hdl.handle.net/1974/1990.

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Stimuli-responsive hydrogels swell or contract in response to external pH, ionic strength or temperature, and are of considerable interest as pharmaceutical controlled release devices. Alginate, a linear polysaccharide consisting of mannuronic and guluronic acids, was used as starting material in semisynthesis of pH-responsive hydrogel. Linear alginate was chemically modified with di-aldehyde via acid-catalyzed acetalization, forming a tetrafunctional acetal-linked semisynthetic network alginate polymer (SNAP) with carboxylate moieties preserved as stimuli-responsive sensors. The kinetics of acetalization were found to undergo zero and second-order reaction with respect to di-aldehyde and alginate respectively. With the determined rate constant of 19.06 L•mole-1•s-1 at 40oC and activation energy of 78.58 kJ•mol-1, a proposed predictive reaction model may be used a priori to select reaction conditions providing specific polymer properties. Gel swelling and average pore size were then able to be kinetically or thermodynamically controlled between 80-1000 fold and 30 nm-1 m respectively. As a proof of concept, SNAP hydrogel was fine-tuned with specific swelling and pore sizes for absorptive encapsulation and controlled release of a wide spectrum of molecular sizes of proteins ranging between 1.3 to 546 kDa. SNAP hydrogels/granules demonstrated limited swelling in the simulated gastric environment, protecting proteins from enzymatic and acid degradation, while swelling in alkaline media, releasing active therapeutics in a simulated intestinal lumen (pH ~ 7.8), so is under the consideration as an oral delivery vehicle for protein therapeutics. A constitutive polyelectrolyte gel model based on non-Gaussian polymer elasticity, Flory-Huggins liquid lattice theory, and non-ideal Donnan-membrane equilibria was derived, to describe SNAP gel swelling in dilute and ionic solutions. The derived model accurately describes the SNAP hydrogel swelling in acid and alkaline solutions of wide range of ionic strength. The pore sizes of SNAP hydrogel were estimated by the derived model and were comparable to those determined experimentally by thermoporometry and protein diffusion. The derived model can characterize hydrogel structure such as molecular weight between crosslinks, or can be used as predictive model for swelling and pore size if gel structural information is known, and can potentially be applied to other point-link network polyelectrolytes such as hyaluronic acid gel.
Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2009-07-20 11:48:17.508

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Wang, Weinan [Verfasser]. "Structure and kinetic of stimuli-responsive thin hydrogel films / Weinan Wang." 2010. http://d-nb.info/1000455297/34.

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Kim, Jungwook. "Mechanically unstable hydrogel sheets: Formation of stimuli-responsive surfaces and structures." 2011. https://scholarworks.umass.edu/dissertations/AAI3465028.

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A hydrogel is a crosslinked network of polymer chains swollen by water. When immersed in an aqueous medium, a hydrogel will swell by taking up water until the osmotic pressure set by mixing between water and polymer is balanced by the free energy required to stretch polymer chains. When considered at a length scale greater than the sub-micrometer scale inhomogeneity of the gel network structure, the unconstrained gel swells isotropically and reaches a macroscopically stress free state. However, when a sheet of gel is attached to either a non-swelling rigid substrate or a gel that swells by a different amount, the resulting mechanical constraints generate stress within the gel, leading to the out-of-plane deformations of the gel. In this thesis, we study and harness the instabilities of these mechanically constrained hydrogels, especially thin hydrogel sheets with thicknesses of 10–100 micrometers that swell and deswell rapidly (less than 10 seconds for sufficiently hydrophilic gels). We create hydrogel based micro-systems, where we locally apply mechanical constraints on the swelling of hydrogel sheets, and therefore, the gels deform out-of-plane into 3D shapes. Next, we experimentally characterize and analyze the deformed hydrogels, elucidate the mechanisms underlying the observed deformation using finite element analysis, and finally utilize these methods to fabricate stimuli-responsive surfaces and structures. As the first example, we attach a thin film of hydrogel on a rigid substrate, inducing an elastic creasing instability in which the surface of the hydrogel locally folds against itself. Through the chemical modification of the hydrogel surfaces that undergo the creasing instability, we fabricate dynamic surfaces that hide and display biomolecular patterns in response to an external stimulus and show how these materials hold promise for applications in studying cell mechanics and creating lab-on-a-chip devices. Next, we use a grayscale gel lithography to two-dimensionally patterned discretely varying swelling ratios within a hydrogel sheet of ∼ 10 micrometer thickness. This finite-thickness, differentially growing hydrogel sheet undergoes out-of-plane deformation as it swells and adopts a configuration that is determined by the initially prescribed local swelling ratios and minimizes the overall elastic deformation energy, i.e. the sum of stretching and bending energies. Additionally, we introduce a halftone-style two-level grayscale gel lithography, which prescribes effectively continuous metrics on the hydrogel sheets by patterning hexagonal arrays of dots that locally vary in their sizes and swell less than the background. This platform, grayscale gel lithography, provides opportunities both for asking fundamental questions about the mechanics of non-Euclidean plates, as well as for designing stimuli-responsive micro-devices.

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Matos, Inês Fernandes. "Stimuli responsive injectable hydrogels for local delivery of anticancer drugs." Master's thesis, 2013. http://hdl.handle.net/10451/29597.

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Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2014
Stimuli-sensitive hydrogels are polymer solutions that gel in response to environmental stimuli (physical, chemical or biological). One of the most recent trends in hydrogel research is in situ hydrogel formation. In situ thermo-sensitive hydrogels, which are solutions at room temperature and gel under physiological conditions, have been widely explored. Chenite et al (2000) reported that chitosan (C) combined with glycerophospahte (GP) becomes thermo- sensitive in diluted acids and can undergo gelation at 37ºC. C/GP systems have been considered for sustained local drug delivery in cancer treatment. Although, all formulations reported in literature exhibit a high concentration of GP, concerns regarding GP toxicity have arisen. In this study 21 solutions with different combinations of C1.0-2.0 % (w/v) mixed with 7.0-2.5 % (w/v) of GP were prepared with the aim of developing an injectable in situ hydrogel with the minimum amount of GP to be used as a drug delivery system for localized cancer therapy. Gelation time of all solutions was studied. Rheological assays at room temperature and at 4ºC were performed for selected solutions, in order to evaluate the solutions’ injectability and stability. Results suggest that C/GP solutions with low concentrations of GP have the potential to be used as injectable in situ gelling thermosensitive formulations. From all formulations studied, C 1.0% (w/v) formulations exhibited more stable and lower viscosity values, and, consequently, better injectability at 4ºC and room temperature. However, they presented a slow gelation time. On the other hand, C 2.0% (w/v) formulations exhibited fast gelation times, but their injectability was more difficult comparing with the previous formulations.
Hidrogeles sensíveis a estímulos são soluções de polímeros que gelificam como resposta a um estímulo ambiental (físico, químico ou biológico). Hidrogeles in situ têm sido alvo de crescente atenção. Hidrogeles termo-sensíveis in situ que são soluções à temperature ambiente e que gelificam em condições fisiológicas têm sido extensamente estudados. Chenite al (2000) reportaram que quitosano (C) combinado com glicerofosfato (GP), quando diluído numa solução acídica, gelifica a 37ºC. Hidrogeles C/GP têm sido considerados no desenvolvimento de sistemas de administração local de libertação prolongada no tratamento de cancro. Apesar de todas as formulações reportadas na literatura utilizarem elevadas concentrações de GP, algumas questões relativamente à sua toxicidade têm sido levantadas. Com o objectivo de obter uma formulação de administração local e libertação prolongada para fármacos anti-cancerígenos, 21 soluções com diferentes combinações de C, 1.0-2.0 % (m/v), e GP, 7.0-2.5 % (m/v), foram preparadas. O tempo de gelificação de todas as soluções foi estudado. Estudos reológicos à temperatura ambiente e a 4ºC foram efectuados a soluções seleccionadas de forma a avaliar a sua injectabilidade e estabilidade. Os resultados sugerem que soluções com menor concentração de GP têm potencial para serem usadas em formulações in situ termosensíveis. Formulações com C a 1.0% (m/v) demonstraram maior estabilidade e menor viscosidade (melhor injectabilidade) a ambas as temperaturas. Contudo, quando comparadas com as formulações anteriores, formulações com C a 2.0% (m/v) demonstraram menores tempos de gelificação e menor injectabilidade.
Università degli Studi di Sassari, Facoltà di Farmacia

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Caldorera-Moore, Mary. "Development and optimization of shape-specific, stimuli-responsive drug delivery nanocarriers using Step and Flash Imprint Lithography." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-05-833.

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The advent of highly sophisticated drugs designed to interfere with specific cellular functions has created the demand for “intelligent” carriers that can efficiently deliver therapeutic agents in response to a pathophysiogical condition. Nanoscale intelligent systems can maximize the efficacy of therapeutic treatments in numerous ways because they have the ability to rapidly detect and response to disease states directly at the site and sparing physiologically healthy cells and tissues, thereby improving a patient’s quality of life. Nanoparticle fabrication has primarily relied on emulsions, self-assembly and micelles based methods which inherently generate polydisperse spherical particles with little control over particle geometry. Despite significant progress in such drug delivery systems, critical limitations remain in synthesizing nanocarriers with highly controllable architecture (size, shape or aspect ratio) that can, at the same time, impart response-sensitive release mechanisms. These parameters are essential for controlling the in-vivo transport, bio-distribution, and drug release mechanisms. The objective of my dissertation is to employ the nanofabrication technique Step and Flash Imprint Lithography (S-FIL) to synthesize stimuli-responsive nanocarriers of precise architectures and composition. Applying S-FIL technology, fabrication of nanocarriers of a variety of shapes and sizes (down to 36nm length scale) that are also environmentally responsive by incorporating enzymatically-degradable peptides into the nanocarrier hydrogel matrix, to provide triggered release of encapsulated therapeutic agents in response to specific pathophysiological conditions, has been accomplished. Besides disease-responsive release, the two key properties of an effective nanocarrier are (a) efficient targeting to specific tissues and cells and (b) avoiding rapid clearance and remaining in circulation in the blood stream for a significant amount of time to increase particle uptake in target tissues. These two properties are expected to be dependent on the shape and size of the carriers. Using various shape and size S-FIL fabricated nanoparticles, the effects of particle geometry on intracellular uptake has also been evaluated. In this dissertation, I will present the extensive work that has been done in the fabrication and optimization of the S-FIL nanocarriers, evaluation of the nanocarrier’s in vitro properties, and evaluation of the effects of nanocarrier geometry on intracellular uptake.
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Valente, Bárbara Sofia dos Reis. "Synthesis and characterization of ionic liquid based polyampholyte hydrogels." Master's thesis, 2016. http://hdl.handle.net/10316/81564.

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Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia
O desenvolvimento de novas áreas de pesquisa sobre líquidos iónicos deve-se às suas propriedades únicas e ao facto da pesquisa desenvolvida ao longo de vários anos apontar um trabalho bastante significativo no leque dos materiais que sejam capazes de atender às necessidades presentes, pensando já nas futuras. As áreas de potencial interesse são notavelmente amplas e as propriedades ímpares dos líquidos iónicos envolvem vastas áreas de aplicação, incluindo sistemas de extração/separação (fases estacionárias para cromatografia), meios de síntese e reação (electrólitos em electroquímica e polimerização também como uma nova geração de solventes). Contudo, ainda existe muito trabalho a ser desenvolvido, sobretudo devido aumento significativo da variedade de líquidos iónicos presentes atualmente no mercado, o que significa também que existe um vasto leque de oportunidades pronto para o desenvolvimento. O principal objectivo deste trabalho recai sobre o desenvolvimento e caracterização de hidrogéis super absorventes à base de 2-hydroxyethyl methacrylate (HEMA) que foram sintetizados por polimerização radicalar vinílica. Estes hidrogéis foram projetados de forma a conterem diferentes razões molares de catiões e aniões, fornecidos pelos monómeros vinílicos 1-butyl-3-vinylimidazolium chloride (BVImCl) and 3-sulphopropyl-acrylate potassium (SPAK), respectivamente. Os hidrogéis que resultaram deste processo são, por definição, polímeros anfolíticos, podendo ter inúmeras aplicações. Os materiais preparados foram posteriormente caracterizados através de várias técnicas. Análise elementar, FTIR de transmissão e SEM que permitiram assegurar a homogeneidade das amostras e ainda a modificação do poli(HEMA) com grupos funcionais catiónicos e aniónicos; propriedades termo-mecânicas avaliadas através de análise termogravimétrica, DSC e testes de tração, que demonstraram que os hidrogéis têm uma estabilidade térmica relativamente elevada e que os polímeros anfolíticos apresentam propriedades mecânicas bastante interessantes devido à reticulação iónica estabelecida devido à interação entre os grupos catiónicos e aniónicos existentes na matriz do hidrogel; os resultados sobre a capacidade de sorção de água que revelaram hidrogéis super absorventes à base de poli(HEMA) podem ser obtidos pela técnica aplicada neste trabalho. Os polielectrólitos catiónicos e aniónicos apresentaram um grau de sorção particularmente elevado, pois foram capazes de aumentar o seu tamanho cerca de 100 vezes relativamente à sua massa seca, quando imersos em água. Para além disso, estes hidrogéis destacaram-se como sendo bastante sensíveis à força iónica do meio em que foram mergulhados. Uma vantagem destes sistemas em particular, quando comparados com os polielectrólitos convencionais, é que devido à presença de grupos iónicos em vez de grupos ionizáveis, estes não são sensíveis ao pH do meio, permitindo assim a sua aplicação em praticamente toda a gama de pH disponível. Finalmente, os hidrogéis catiónicos e aniónicos preparados neste trabalho apresentam-se com tendo capacidade para adsorver diferentes moléculas carregadas, nomeadamente metais, corantes aniónicos e aminoácidos, com capacidades de sorção superiores a 80% para o ião cromato, 95% para o verde de bromocresol e ainda 70% para o aminoácido, respectivamente. Os resultados obtidos nesta tese demonstraram que é possível funcionalizar hidrogéis preparados a partir de poli(HEMA), de forma a obter diferentes polielectrólitos, dependendo da razão entre monómeros catiónicos e aniónicos utilizados. É possível encontrar inúmeras aplicações para os hidrogéis apresentados que podem ir desde adsorção de moléculas carregadas para tratamento de águas residuais ou separação de biomoléculas, para o caso dos polielectrólitos aniónicos e catiónicos, até ao desenvolvimento de hidrogéis sensíveis a estímulos externos, ou polímeros inteligentes, com uma boa estabilidade mecânica, para o caso dos polímeros anfolíticos preparados.
The development of new research areas on ionic liquids are due to their unique properties and over the years remarkable work has been done in order to develop materials that can fulfill the present and future needs. The potential application areas are extremely vast and the distinctive properties of IL carry several application areas, including extraction systems (stationary phases for chromatography), reaction and synthesis medias (electrolytes in electrochemistry and polymerization processes and as a new generation of solvents). However, there is still a lot to study and develop, especially because of the massive variety of ionic liquids currently available. Therefore it opens a wide range of opportunities and is still an open field ready to be explored. The aim of this work was to develop and characterize 2-hydroxyethyl methacrylate (HEMA) based superabsorbent ionic hydrogels synthesized by free radical vinyl polymerization. These ionic hydrogels were designed to contain different cationic and anionic molar ratios provided by the vinyl monomers 1-butyl-3-vinylimidazolium chloride (BVImCl) and 3-sulphopropyl-acrylate potassium (SPAK), respectively. The resulting hydrogels are, by definition, polyampholytes, which will have numerous applications. The prepared polyampholytes were characterized according to several techniques. Elemental analysis, transmission FTIR and SEM permitted to confirm the homogeneity of the samples and that poly(HEMA) was indeed modified with the cationic and anionic functional groups; thermo-mechanical properties, evaluated by thermogravimetric analysis, DSC and tensile tests, showed that the hydrogels have a relatively high thermal stability and that the neutral polyampholytes present interesting mechanical properties due to the ionic crosslinking that is established between cationic and anionic groups existing in the hydrogel network; the water swelling capacity results revealed that superabsorbent poly(HEMA) based hydrogels can be obtained by the applied strategy. Cationic and anionic polyelectrolytes exhibited particularly high water swelling degree and were able to increase 100 times their own dry weight when immersed in water. Moreover these hydrogels are very sensitive to changes in the ionic strength of the media in which they are immersed. An advantage of these particular systems when compared to conventional polyelectrolytes is that due to the presence of ionic instead of ionizable groups, they will not be sensitive to pH, allowing its application in all nearly all pH ranges. Finally, the prepared cationic and anionic hydrogels presented potential capacity to adsorb different charged molecules, namely a metal ion, an anionic dye and an aminoacid with adsorption capacities higher than 80% for chromate, 95% bromocresol green and 70% for L-tryptophan, respectively. The results presented in this work showed that it is possible to functionalize poly(HEMA) based hydrogels to prepare different types of polyelectrolytes depending on the used ratio of cationic and anionic monomers. Those ionic hydrogels may find different type of applications that can range from the adsorption of charged molecules for wastewater treatment or biomolecules separation, in the case of the cationic and anionic polyelectrolytes, or for the development of stimuli-responsive hydrogels with good mechanical stability in the case of the prepared polyampholytes.

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Pini, Cesare. "Microfluidic Systems based on Chemical Volume-Phase-Transition Stimuli-Responsive Hydrogels." 2017. https://tud.qucosa.de/id/qucosa%3A32755.

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Microfluidics is an expanding research field that lies at the interface of engineering, physics, chemistry and biology and offers promises in the development in a wide range of applications from point-of-care (POC) diagnostics to regenerative medicine, from drug testing to DNA sequencing. The number of publications in the field has been steadily growing in the last two decades and the trend does not show any sign of slowing down. On top of that, the market value generated by microfluidics is expected to quadruple in the time spam from 2013 to 2023: from 1.59 billion dollars in 2013, it is expected to grow to 8.64 billion dollars in 2023. There are however a series of limitations which prevent the full development of microfluidic technology. As it has already been pointed out in many publications in the last decade, the lack of a killer application capable of really making the difference out of the research labs and the academic playgrounds around the world is an impeding factor to the full-scale development of microfluidcs at an industrial level, also due to the lack of industrial standards. A number of authors, though, are of the opinion that the actual concept itself needs to challanged and that a complete re-thinking of the current technological platform should be done in order to make the breakthrough advance allowing a long-standing promising field to finally realise itself.In this work a completely new concept, based on volume-phase-transition smart-hydrogels, is presented and the foundations for a transistor-like technological platform are laid. A strong focus is therefore based on the basic element itself, i.e. volume-phase-transition smart-hydrogels, and on the possible ways that it might be integrated in microfluidic systems. Furthermore, basic circuits that lay the foundations for a logic system are presented together with other applications that replicate some elementary functions in microelectronics, such as oscillators. Finally, integration of logic gates as well as basic circuits is presented, in order to lay the foundations for chemical integrated microfluidic circuits.

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Huang, Hui Yu. "Studies of stimuli-responsive hydrogel nanoparticle containing membranes and the development of a closed-loop glucose-responsive insulin delivery device /." 2008. http://proquest.umi.com/pqdlink?did=1659961721&sid=4&Fmt=2&clientId=12520&RQT=309&VName=PQD.

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Riedel, Stefanie. "High-Energy Electron-Treatment of Collagen and Gelatin Hydrogels: Biomimetic Materials, Stimuli-Responsive Systems and Functional Surfaces." 2019. https://ul.qucosa.de/id/qucosa%3A35460.

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Biological hydrogels such as collagen and gelatin are highly attractive materials for tissue engineering and biomedicine. Due to their excellent biocompatibility and biodegradability, they represent promising candidates in regenerative medicine, cell culture, tissue replacement and wound dressing applications. Thereby, precisely tuned material properties are indispensable for customization. High-energy electron-treatment is a highly favourable crosslinking technique to tailor the material properties. In five sub-projects, this thesis investigates the potential of high-energy electron-treatment to precisely modify collagen hydrogels, to develop thermo- as well as hydration-sensitive systems and functional surfaces from gelatin for biomedical applications. The first sub-project focusses on the modification of collagen hydrogels by electron-induced crosslinking with potential application as biomimetic extracellular matrix material. Thereby, it is shown that the material properties can be precisely tailored by adapting electron-induced crosslinking while high cytocompatibility is maintained. Within the second sub-project, an electron-crosslinking-induced shape-memory effect in gelatin is described in order to develop a thermo-responsive system. The effect is described experimentally as well as theoretically to demonstrate the fundamental physical processes. The third sub-project develops an electroncrosslinked hydration-sensitive gelatin system. The work discusses how swelling of electroncrosslinked gelatin is influenced by the pH-value and salt concentration of the swelling liquid. Thereby, response of the hydration-sensitive gelatin system can be further modified towards biological actuatoric systems. The fourth sub-project develops a two-step process to mechanically pattern gelatin surfaces. Within the first step, thin gelatin surfaces are mechanically patterned by a highly focussed electron beam. In a second step, they are stabilized by homogeneous electron-crosslinking for applications at physiological conditions. Another method to develop functional gelatin surfaces is described in the last sub-project. Here, gelatin is topographically patterned via a moulding technique. The resulting micro-structures are then stabilized via electron-crosslinking. In addition, the presented work investigates pattern transfer, long time stability at physiological conditions as well as cytocompatibility.:1 Introduction and Objective 1.1 Biomimetic ECM Models 1.2 Stimuli-Responsive Hydrogels 1.3 Functional Hydrogel Surfaces 2 General Background 2.1 Hydrogels 2.1.1 Collagen 2.1.2 Gelatin 2.2 Polymer Crosslinking 2.2.1 High-Energy Electron-Treatment of Polymers 2.2.2 Electron-Irradiation-Induced Crosslinking of Gelatin 2.3 High-Energy Electron Accelerator 3 Cumulative Part 3.1 High-Energy Electron-Induced Modification of Collagen 3.2 Thermo-Responsive Gelatin System 3.3 Hydration-Responsive Gelatin System 3.4 Mechanically Patterned Gelatin Surfaces 3.5 Topographically Patterned Gelatin Surfaces 4 Summary and Conclusion 5 Outlook Bibliography Author Contributions List of Abbreviations List of Figures Acknowledgements Scientific Curriculum Vitae Publication List Selbstständigkeitserklärung
Biologische Hydrogele wie Kollagen und Gelatine sind wichtige Materialien vor allem in biomedizinischen Anwendungsbereichen. Durch deren exzellente Biokompatibilität und biologische Abbaubarkeit werden sie vor allem bei der Züchtung von biomimetischem Gewebe, in der Zellkultur, als Gewebeersatz in der regenerativen Medizin oder auch als Wundverband eingesetzt. In der Verwendung solcher Materialien besteht eine wesentliche Herausforderung darin, deren Eigenschaften so präzise wie möglich einzustellen, um speziell angepasste Substrate und Gewebe entwickeln zu können. Eine äußerst vorteilhafte Methode zu Adaptierung der Materialeigenschaften ist die elektronenstrahlbasierte Vernetzung, die auf die Verwendung zusätzlicher chemischer Vernetzer verzichtet. Die vorgelegte Arbeit untersucht in fünf Teilprojekten das Potential von Elektronenstrahlvernetzung zur Modifizierung von Kollagen- sowie Gelatinehydrogelen für biomedizinische Anwendungen. Das erste Teilprojekt fokussiert sich auf die Auswirkungen hochenergetischer Elektronen auf Kollagenhydrogele und deren Eigenschaften für potentielle Anwendungen als biomimetisches Modell der extrazellulären Matrix. Dabei wird gezeigt, dass sich die Materialeigenschaften in Abhängigkeit der Elektronenbestrahlung präzise einstellen lassen und dass diese Gele eine hohe Zellkompatibilität aufweisen. Das zweite Teilprojekt beschreibt den Effekt des thermischen Formgedächtnisses in Gelatine nach Elektronenstrahlvernetzung und dessen Potential für die Entwicklung biologischer Aktuatoren. Die Effizienz des Formgedächtniseffekts wird in diesem Teilprojekt ausführlich theoretisch beschrieben und mit experimentellen Untersuchungen an Gelatine verglichen. Im dritten Teilprojekt wird ein elektronenstrahlvernetztes, hydrations-responsives Gelatinesystem beschrieben. Zusätzlich wird der Einfluss von pH-Wert und Salzkonzentration der Quelllösung auf das Quellen von elektronenstrahlvernetzter Gelatine untersucht um das Reaktionsverhalten noch präziser einstellen zu können. Das vierte Teilprojekt beschreibt einen Zwei-Schritt-Prozess, bei dem dünne Gelatineschichten mittels hochenergetischer Elektronen mechanisch funktionalisiert werden können. Dabei wird in einem ersten Schritt die Oberfläche durch hoch fokussierte Elektronen mechanisch strukturiert, um im zweiten Schritt mittels homogener Elektronenstrahlvernetzung für die Anwendung unter physiologischen Bedingungen stabilisiert zu werden. Eine weitere Methode zur Funktionalisierung der Oberfläche von Gelatinehydrogelen wird im letzten Teilprojekt dieser Arbeit dokumentiert. Dabei werden topographische Mikrostrukturen auf Gelatineoberflächen aufgebracht und mittels Elektronenstrahlvernetzung stabilisiert. Dieses Teilprojekt untersucht zusätzlich den Strukturtransfer, die Langzeitstabilität unter physiologischen Bedingungen sowie die Zellkompatibilität.:1 Introduction and Objective 1.1 Biomimetic ECM Models 1.2 Stimuli-Responsive Hydrogels 1.3 Functional Hydrogel Surfaces 2 General Background 2.1 Hydrogels 2.1.1 Collagen 2.1.2 Gelatin 2.2 Polymer Crosslinking 2.2.1 High-Energy Electron-Treatment of Polymers 2.2.2 Electron-Irradiation-Induced Crosslinking of Gelatin 2.3 High-Energy Electron Accelerator 3 Cumulative Part 3.1 High-Energy Electron-Induced Modification of Collagen 3.2 Thermo-Responsive Gelatin System 3.3 Hydration-Responsive Gelatin System 3.4 Mechanically Patterned Gelatin Surfaces 3.5 Topographically Patterned Gelatin Surfaces 4 Summary and Conclusion 5 Outlook Bibliography Author Contributions List of Abbreviations List of Figures Acknowledgements Scientific Curriculum Vitae Publication List Selbstständigkeitserklärung

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Simmons, David Samuel. "Phase and conformational behavior of LCST-driven stimuli responsive polymers." 2009. http://hdl.handle.net/2152/18155.

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Several analytical mean field models are presented for the class of stimuli responsive polymers that are driven by the lower critical solution temperature (LCST) transition. For solutions above the polymer crossover concentration, a hybrid model combines lattice-fluid excluded volume and van-der-Waals interactions with a combinatorial approach for the statistics of hydrogen bonding, hydration, and ionic bonding. This approach yields models for the LCST of both neutral polymers and lightly charged polyelectrolytes in aqueous salt solution. The results are shown to be in semi-quantitative agreement with experimental data for the cloud point of polyethylene oxide (PEO) in aqueous solution with various salts, and some aspects of the lyotropic series are reproduced. Results for lightly charged polyelectrolytes are compared to and shown to be in qualitative agreement with aspects of experimentally observed behavior. Finally, a framework is established for extension of these models to further aspects of the lyotropic series and polyelectrolyte behavior. At the nanoscale, lattice fluid (LF) and scaled particle theory (SPT) approaches are employed to model the LCST-related coil-globule-transition (CGT) of isolated polymer chains in highly dilute solution. The predicted CGT behavior semi-quantitatively correlates with experimental results for several polymer-solvent systems and over a range of pressures. Both the LF and SPT models exhibit a heating induced coil-to-globule transition (HCGT) temperature that increases with pressure until it merges with a cooling induced coil-to-globule transition (CCGT). The point at which the CCGT and HCGT meet is a hypercritical point that also corresponds to a merging of the lower critical and upper critical solution temperatures. Theoretical results are discussed in terms of a generalized polymer/solvent phase diagram that possesses three hypercritical points. Within the lattice model, a dimensionless transition temperature [author gives mathematical symbol] is given for a long chain simply by the equation [author gives mathematical equation], where [part of the equation] is the bulk solvent occupied volume fraction at the transition temperature. Furthermore, there is a critical value of the ratio of polymer to solvent S-L characteristic temperature below which no HCGT transition is predicted for an infinite chain.
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Kaplan, Jonah Andrew. "Mechanoresponsive drug delivery materials." Thesis, 2015. https://hdl.handle.net/2144/13708.

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Stimuli-responsive drug delivery materials release their payloads in response to physiological or external cues and are widely reported for stimuli such as pH, temperature, ionic strength, electrical potential, or applied magnetic field. While a handful of reports exist on materials responsive to mechanical stimuli, this area receives considerably less attention. This dissertation therefore explores three-dimensional networks and polymer-metal composites as mechanoresponsive biomaterials by using mechanical force to either trigger the release of entrapped agents or change the conformation of implants. At the nanoscale, shear is demonstrated as a mechanical stimulus for the release of a monoclonal antibody from nanofibrous, low molecular weight hydrogels formed from bio-inspired small molecule gelators. Using their self-healing, shear-thinning properties, mechanoresponsive neutralization of tumor necrosis factor alpha (TNFα) in a cell culture bioassay is achieved, suggesting utility for treating rheumatoid arthritis. Reaching the microscale, mechanical considerations are incorporated within the design of cisplatin-loaded meshes for sustained local drug delivery, which are fabricated through electrospinning a blend of polycaprolactone and poly(caprolactone-co-glycerol monostearate). These meshes are compliant, amenable to stapling/suturing, and they exhibit bulk superhydrophobicity (i.e., extraordinary resistance to wetting), which sustains release of cisplatin >90 days in vitro and significantly delays tumor recurrence in an in vivo murine lung cancer resection model. This polymer chemistry/processing strategy is then generalized by applying it to the poly(lactide-co-glycolide) family of biomedical polymers. As a macroscopic approach, a tunable, tension-responsive multilayered drug delivery device is developed, which consists of a water-absorbent core flanked by two superhydrophobic microparticle coatings. Applied strain initiates coating fracture to cause core hydration and subsequent drug release, with rates dependent on strain magnitude. Finally, macroscopic, shape-changing polymer-composite materials are developed to improve the current functionality of breast biopsy markers. This shape change provides a means to prevent marker migration from its intended site—a current clinical problem. In summary, mechanoresponsive systems are described, ranging from the nano- to macroscopic scale, for applications in drug delivery and biomedical devices. These studies add to the nascent field of mechanoresponsive biomedical materials and the arsenal of drug delivery techniques required to combat cancer and other medical ailments.
2017-10-27T00:00:00Z

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"Development of Stimuli-responsive Hydrogels Integrated with Ultra-thin Silicon Ribbons for Stretchable and Intelligent Devices." Master's thesis, 2012. http://hdl.handle.net/2286/R.I.15046.

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abstract: Electronic devices based on various stimuli responsive polymers are anticipated to have great potential for applications in innovative electronics due to their inherent intelligence and flexibility. However, the electronic properties of these soft materials are poor and the applications have been limited due to their weak compatibility with functional materials. Therefore, the integration of stimuli responsive polymers with other functional materials like Silicon is strongly demanded. Here, we present successful strategies to integrate environmentally sensitive hydrogels with Silicon, a typical high-performance electronic material, and demonstrate the intelligent and stretchable capability of this system. The goal of this project is to develop integrated smart devices comprising of soft stimuli responsive polymeric-substrates with conventional semiconductor materials such as Silicon, which can respond to various external stimuli like pH, temperature, light etc. Specifically, these devices combine the merits of high quality crystalline semiconductor materials and the mechanical flexibility/stretchability of polymers. Our innovative system consists of ultra-thin Silicon ribbons bonded to an intelligently stretchable substrate which is intended to interpret and exert environmental signals and provide the desired stress relief. As one of the specific examples, we chose as a substrate the standard thermo-sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel with fast response and large deformation. In order to make the surface of the hydrogel waterproof and smooth for high-quality Silicon transfer, we introduced an intermediate layer of poly(dimethylsiloxane) (PDMS) between the substrate and the Silicon ribbons. The optical microscope results have shown that the system enables stiff Silicon ribbons to become adaptive and drivable by the soft environmentally sensitive substrate. Furthermore, we pioneered the development of complex geometries with two different methods: one is using stereolithography to electronically control the patterns and build up their profiles layer by layer; the other is integrating different multifunctional polymers. In this report, we have designed a bilayer structure comprising of a PNIPAAm hydrogel and a hybrid hydrogel of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA). Typical variable curvatures can be obtained by the hydrogels with different dimensional expansion. These structures hold interesting possibilities in the design of electronic devices with tunable curvature.
Dissertation/Thesis
M.S. Chemical Engineering 2012

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Gil, Eun Seok. "Stimuli-responsive protein-based hydrogels by utilizing [beta]-sheet conformation of silk fibroin as cross-links." 2004. http://www.lib.ncsu.edu/theses/available/etd-12282004-173030/unrestricted/etd.pdf.

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Koetting, Michael Clinton. "Stimulus-responsive delivery systems for enabling the oral delivery of protein therapeutics exhibiting high isoelectric point." Thesis, 2015. http://hdl.handle.net/2152/30484.

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Protein therapeutics offer numerous advantages over small molecule drugs and are rapidly becoming one of the most prominent classes of therapeutics. Unfortunately, they are delivered almost exclusively by injection due to biological obstacles preventing high bioavailability via the oral route. In this work, numerous approaches to overcoming these barriers are explored. PH-Responsive poly(itaconic acid-co-N-vinylpyrrolidone) (P(IA-co-NVP)) hydrogels were synthesized, and the effects of monomer ratios, crosslinking density, microparticle size, protein size, and loading conditions were systematically evaluated using in vitro tests. P(IA-co-NVP) hydrogels demonstrated up to 69% greater equilibrium swelling at neutral conditions than previously-studied poly(methacrylic acid-co-N-vinylpyrrolidone) hydrogels and a 10-fold improvement in time-sensitive swelling experiments. Furthermore, P(IA-co-NVP) hydrogel microparticles demonstrated up to a 2.7-fold improvement in delivery of salmon calcitonin (sCT) compared to methacrylic acid-based systems, with a formulation comprised of a 1:2 ratio of itaconic acid to N-vinylpyrrolidone demonstrating the greatest delivery capability. Vast improvement in delivery capability was achieved using reduced ionic strength conditions during drug loading. Use of a 1.50 mM PBS buffer during loading yielded an 83-fold improvement in delivery of sCT compared to a standard 150 mM buffer. With this improvement, a daily dose of sCT could be provided using P(IA-co-NVP) microparticles in one standard-sized gel capsule. P(IA-co-NVP) was also tested with larger proteins urokinase and Rituxan. Crosslinking density provided a facile method for tuning hydrogels to accommodate a wide range of protein sizes. The effects of protein PEGylation were also explored. PEGylated sCT displayed lower release from P(IA-co-NVP) microparticles, but displayed increased apparent permeability across a Caco-2 monolayer by two orders of magnitude. Therefore, PEG-containing systems could yield high bioavailability of orally delivered proteins. Finally, a modified SELEX protocol for cellular selection of transcellular transport-initiating aptamers was developed and used to identify aptamer sequences showing enhanced intestinal perfusion. Over three selection cycles, the selected aptamer library showed significant increases in absorption, and from an initial library of 1.1 trillion sequences, 5-10 sequences were selected that demonstrated up to 10-fold amplification compared to the naïve library. These sequences could provide a means of overcoming the significant final barrier of intestinal absorption.
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Kanaan, Akel Ferreira. "Ionic liquid based functionalized materials for the development of multi-responsive electroactive hydrogels." Doctoral thesis, 2021. http://hdl.handle.net/10316/95400.

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Tese no âmbito do doutoramento em Engenharia Química, apresentada ao Departamento de Engenharia Química da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.
The main objective of the present thesis was the development and characterization of novel electroactive ionic liquid-based polycationic hydrogels. These materials were obtained by the functionalization of natural-origin and/or synthetic polymers with an ionic liquid-based vinyl monomer (functionalized at the cation) by two different approaches, namely by the formation of semi-interpenetrating polymer networks (s-IPNs) and by copolymerization with a non-charged comonomer. Through this doctoral work, three different multi-responsive systems were developed targeting a broad range of applications, such as, drug delivery devices, bioseparators, soft actuators, tissue engineering scaffolds, iontophoretic patches and wound dressings. The first approach was employed to obtain multi-responsive s-IPNs hybrid structures based on natural polymers (starch and chitosan) and homopolymers/copolymers of poly(1-butyl-3-vinylimidazolium chloride) (poly(BVImCl) and poly(2-hydroxyethyl methacrylate-co-1-butyl-3-vinylimidazolium chloride) (poly(HEMA-co-BVImCl)). In the case of the starch-based s-IPNs, results demonstrated that the sorption/release capacity of these hydrogels towards L-tryptophan (used as a model biomolecule) could be adjusted depending on the intensity of the applied DC voltage and/or sorption/release medium. It was also confirmed that the process employed to dry the hydrogels (oven and freeze-drying) has a major influence on the conductivity of the materials and that freeze-drying induced higher conductivity values. Furthermore, biological tests demonstrated that the prepared s-IPNs were able to guarantee fibroblasts viability. These newly obtained hybrid materials demonstrated to have potential to be employed for bio-separation processes and for the sustained delivery of specific charged-biomolecules. In the case of the chitosan-based s-IPNs it was demonstrated that the prepared hybrid hydrogels presented enhanced mechanical properties, water swelling capacities (at different pH and ionic strengths) and sorption capacities towards charged molecules when compared to pristine chitosan. Obtained s-IPN hydrogels also demonstrated to have modulated lidocaine hydrochloride permeation/delivery profiles at low current densities (0.56 mA/cm2) and as a function of their charge density. Moreover, biological tests showed that the prepared s-IPN hydrogels were non-hemolytic and presented potential hemostatic capability. These “smart” s-IPNs presented advantageous properties for the design of topical iontophoretic patches and/or hemostatic agents. The second approach was employed to obtain multi-responsive electro-actuating hydrogels based on poly(HEMA-co-BVImCl) copolymers. Studies were performed to evaluate the influence of surface properties on the actuating behavior of the hydrogels in different aqueous media, with different pH and ionic strength values. The different surface properties were obtained by simply employing different mold subtracts, with different hydrophobicities (namely Teflon® and glass) during the copolymer free radical polymerization in aqueous media. Obtained results demonstrated that hydrogels synthesized on Teflon® molds presented the highest electro-actuation capacity in aqueous media, with equivalent bending motion on both directions according to the polarization applied. Moreover, it was also noticed that hydrogels surface charge density and water swelling capacity could be modulated depending on the type of mold utilized during polymerization. Resulting soft stimuli-responsive materials can be regarded as “smart” platforms for the design of soft actuators and cell culture scaffolds for biomedical applications. Overall, this PhD thesis allows concluding that the functionalization of natural and/or synthetic polymers with ILs represents a viable and efficient strategy for the development of multi-responsive electroactive materials for applications in biomedicine, (bio)separation and electrochemistry.
O objetivo principal desta tese foi o desenvolvimento e caracterização de novos hidrogéis eletroativos policatiónicos à base de líquidos iónicos. Esses materiais foram obtidos pela funcionalização de polímeros de origem natural e/ou sintéticos com um monómero vinílico à base de líquidos iónico (funcionalizados no catião) por meio de duas diferentes abordagens, nomeadamente redes poliméricas semi-interpenetradas (s-IPNs) e copolimerização com um comonómero não carregado. Durante a realização do trabalho, foram desenvolvidos três sistemas multi-responsívos diferentes visando uma vasta gama de aplicações, por exemplo, dispositivos para a entrega de fármacos, bioseparadores, atuadores soft, scaffolds para engenharia de tecidos, pensos para iontoforese e para tratamento de feridas. A primeira abordagem consistiu na obtenção de s-IPNs híbridos multi-responsívos à base de polímeros naturais (amido e quitosano) e homopolímeros/copolímeros de poli(cloreto de 1-butil-3-vinilimidazólio) (poli(BVImCl) e poli(metacrilato de 2-hidroxietila-co-cloreto de 1-butil-3-vinilimidazólio) (poli(HEMA-co-BVImCl)). No caso dos hidrogéis s-IPNs à base de amido, os resultados demonstraram que a capacidade de sorção/entrega de L-triptofano, usado como biomolécula modelo, poderia ser otimizada consoante a diferença de potencial aplicada e/ou o tipo de meio utilizado na sorção/libertação. O processo de secagem utilizado nos hidrogéis (secagem em estufa e liofilização), provou ter uma influência significativa na condutividade dos materiais estudados, sendo que os foram sujeitos ao processo de liofilização apresentaram valores superiores de condutividade. Concomitantemente, a viabilidade de fibroblastos na presença dos s-IPNs foi comprovada com recurso a testes biológicos. Desta forma, os materiais híbridos e inovadores desenvolvidos nesta abordagem demonstraram potencial para serem utlizados em processos de biosseparação e para entrega contínua de biomoléculas carregadas específicas. No caso dos s-IPNs à base de quitosano, foi demonstrado que os hidrogéis híbridos desenvolvidos apresentaram melhores propriedades mecânicas, capacidades de entumecimento em água (em diferentes condições de pH e força iónica) e capacidades de sorção para moléculas carregadas, quando comparados com o quitosano puro. Os s-IPNs exibiram perfis modulares de permeação/entrega de lidocaína, a baixas intensidades de corrente (0.56 mA/cm2), em função da respetiva densidade de cargas. Além disso, após testes biológicos, os hidrogéis s-IPN provaram ser não-hemolíticos e hemostáticos. Estes s-IPNs “inteligentes” apresentaram propriedades vantajosas para a preparação de pensos tópicos para iontoforese e/ou pensos hemostáticos. A segunda abordagem estudada foi baseada na obtenção de copolímeros electroactuators híbridos multi-responsívos à base de hidrogéis de poli(HEMA-co-BVImCl). A influência das propriedades de superfícies no comportamento de atuação dos hidrogéis em diferentes meios aquosos (com diferentes valores de pH e força iónica), foi avaliada. Diferentes propriedades de superfície foram obtidas pela simples utilização de diferentes moldes com hidrofobicidade distintas, nomeadamente Teflon® e vidro, durante a copolimerização por polimerização radicalar livre, em meio aquoso. Os resultados demonstraram que os hidrogéis preparados em moldes de Teflon® apresentaram superior capacidade de eletroatuação em meio aquoso, com atuação mecânica equivalente em ambas direções, de acordo com a polaridade aplicada. Para além disso, foi também verificado que a densidade de carga na superfície dos hidrogéis e a capacidade de entumecimento em água pode ser modulada de acordo com o tipo de molde utilizado durante a polimerização. Os materiais responsivos a estímulos podem ser equiparados a plataformas “inteligentes” para a produção de atuadores soft e scaffolds para cultura celular em aplicações biomédicas. Em suma, a presente tese de doutoramento permitiu concluir que a funcionalização de polímeros naturais e/ou sintéticos, com ILs, representa uma estratégia viável e eficiente para o desenvolvimento de materiais eletroativos multi-responsívos para aplicações na biomedicina, biosseparação e eletroquímica.

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Castro, Rita Maria de. "DNA/Dendrimer-based films: a novel material with potential biomedical applications." Doctoral thesis, 2018. http://hdl.handle.net/10400.13/2213.

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Abstract:

Nesta tese de doutoramento, foram desenvolvidos novos materiais híbridos, sob a forma de filmes finos, essencialmente baseados em interações eletrostáticas estabelecidas entre moléculas de ácido desoxirribonucleico (ADN) e dendrímeros de poli(amidoamina) (PAMAM). Os dendrímeros PAMAM são moléculas à escala nanométrica que apresentam multi-valência e um baixo índice de polidispersão. Esta classe de moléculas tem sido muito estudada para a entrega de genes e fármacos em células, para além de muitas outras aplicações na área biomédica. Isto apenas é possível devido às suas propriedades físicas, químicas e estruturais, que permitem a interação eletrostática com ácidos nucleicos e conjugação à superfície e/ou encapsulamento de fármacos no seu interior. Neste trabalho, foi tirado proveito da capacidade destas moléculas interagirem com o ADN para obter novos materiais com aplicações biomédicas promissoras.
In this Ph.D. thesis, novel hybrid materials, in the form of films, were prepared, essentially based on electrostatic interactions established between deoxyribonucleic acid (DNA) molecules and poly(amidoamine) (PAMAM) dendrimers. PAMAM dendrimers are nanoscale molecules that show multi-valency and a low degree of polydispersion. These molecules have been widely studied as gene and drug delivery systems, among other biomedical applications. This is only possible due to their physical, chemical and structural properties, which allow for the electrostatic interaction with nucleic acids, surface conjugation and/or encapsulation of drugs. This work took advantage of the easy interaction of dendrimers with DNA to obtain a new material with promising biomedical applications.

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