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Dissertations / Theses on the topic 'Polymers brushes'

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Published: 11 March 2023

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1

Gunkel, Gesine. "Antibiofouling polymer brushes." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608096.

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2

Uğur, Gökce. "Interface Structure of Diblock Copolymer Brushes and Surface Dynamics of Homopolymer Brushes and Bilayers of Untethered Chains on Brushes." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1311005794.

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3

Fleet, Reda Ali. "Synthesis and characterization of glycopolymer brushes." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5132.

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4

Wei, Yuan. "Probing Local Structure and Dynamics of Polymer Brushes with Neutron Scattering." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1624963009022896.

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5

Sun, Liang. "Structure and Dynamics of Swollen Polymer Brushes." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1499675793233755.

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6

Kelby, Timothy Simon. "Smart brushes on flexible substrates : probing the chemomechanical properties of stimulus-responsive polymer brushes." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610331.

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7

Conlin, Emma L. "Design and synthesis of liquid crystalline polymer brushes and hydrogen bonded polymers /." Available to subscribers only, 2005. http://proquest.umi.com/pqdweb?did=1079664771&sid=2&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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8

Piaoran, Ye. "Synthesis of Polymers and Polymer Brushes through RAFT Polymerization via Flow Chemistry." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1491229581133419.

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9

Tan, Khooi Yeei. "Smart surfaces using responsive polymer brushes." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607743.

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10

Yang, Fengyu. "Development of Polyacrylamide-Based Biomaterials in Hydrogels and Brushes." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555603442979042.

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11

Constable, Andrew N. "Functionalization of Silica Micro-capillaries and Silica Nanoparticles via Polymer Brushes." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1221746490.

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12

Chen, Xiaoping. "Synthesis and characterization of polymers incorporating N-alkyl urea-peptoid sequences." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382951885.

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13

Constable, Andrew N. "Functionalization of silica micro-capillaries and silica nanoparticles via polymber brushes." Akron, OH : University of Akron, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1221746490.

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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2008.
"December, 2008." Title from electronic dissertation title page (viewed 12/28/2008) Advisor, Roderic P. Quirk; Committee members, Scott Collins, Ali Dhinojwala, Li Jia, Mark D. Soucek; Department Chair, Ali Dhinojwala; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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14

Beck, Catherine Keel. "Characterization of Spin Coated Polymers in Nano-environments as a Function of Film Thickness." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34548.

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Polymer applications have become more demanding as industry continuously turns to more microscopic parts. Due to the interactions of the polymer chains with the supporting surface and the air interface, the thinner films required for such applications have distinctly different properties than those of the well-defined bulk systems. The goal of the current research is to elucidate the behavior of ultrathin films. Two separate studies were performed on thin films supported on silicon wafer substrates: the first focuses on the viscoelastic cooperativity of thin films, and the second concentrates on the morphological behavior of polymer brush films. For the first study, polymethyl methacrylate films were spin coated onto silicon wafers, and the film thickness was determined using ellipsometry. A series of thin films were examined using techniques such as dielectric analysis and thermal mechanical analysis. The theory of cooperativity, which explains polymeric behavior using the intermolecular and intramolecular forces among polymer chains, was employed to understand the behavior of these thin films. Another type of thin film, a polymer brush, was investigated in the second study. Polymer brushes are formed by chemically bonding one end of many polymer chains to a substrate. The other ends of the chains can interact with the surrounding environment creating a brush-like structure. Constraining one end of a polymer chain alters the behavior of such a thin film. Polymer brushes of the di-block copolymer poly(t-butyl methacrylate) and polystyrene were produced on silicon wafers using spin coating techniques. The effects of both grafting density and solvent washes were analyzed using contact angle analysis and atomic force microscopy. In addition, hydrolysis was successfully performed on existing polymer brush samples to produce polymer brushes of the di-block copolymer polymethyl acrylic acid and polystyrene.
Master of Science
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15

Bialas, Sabrina. "Lambda-orthogonal photoresists." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/212724/1/Sabrina%20Bialas%20Thesis.pdf.

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Light-driven additive manufacturing spans applications from materials technology to the field of medicine. The success of light-based fabrication techniques is founded on the spatiotemporal control over light-induced reactions, allowing to control when and where a material is made. Since different molecules absorb different colours of light, selecting a precise colour of light allows to execute one specific reaction from complex mixtures, while all other molecules remain untouched (a concept called lambda-orthogonality). By embedding such lambda-orthogonal groups into photoresists, it becomes possible to control not only when and where, but also which material is made – all from one photoresist.
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16

Schollier, Audrey. "Probing protein adsorption modes onto poly(ethylene glycol) brushes by neutron reflection." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209952.

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Adsorption of proteins at interfaces has an important role in biotechnological and pharmaceutical applications. Indeed, several undesirable processes are related to protein adsorption, as for example: fouling of contact lenses, clotting on blood contacting devices, triggering inflammation around artificial organs, diminished circulation time of therapeutic proteins and drug bearing liposomes. Neutral water soluble polymers, such as poly(ethylene glycol) (PEG), are used to repress protein adsorption: by coating the surface with a polymer brush, a "cushion" is created between the protein and the surface, that can reduce, or even completely repress the adsorption. Understanding the mechanism that inhibits the adsorption at interfaces is an active field of research, and could lead to relevant improvements in biomaterials performances and design.

A clear understanding of the mechanism of protein adsorption onto polymer brushes is still missing. The first models describing the interactions of a polymer brush with adsorbing particles predicted two adsorption modes: primary adsorption at the grafting surface, and secondary adsorption at the outer edge of the brush (occurring for large cylindrical proteins). Primary adsorption can be repressed by increasing the grafting density of the brush, and secondary adsorption by increasing its thickness, in agreement with the experiments reported in the literature. But experimental evidences (a maximum in the adsorbed amount observed for long brushes) suggested then the existence of a third mode: ternary adsorption within the brush itself, due to attractive interactions between the protein and the brush. Standard techniques can in general only probe the total adsorbed amount. The aim of this work was to separate primary and ternary adsorption isotherms, by using neutron reflectivity and deuterated proteins. As neutrons interact differently with hydrogen and deuterium atoms, the contrast between the hydrogenated brush and the deuterated protein is high enough to separate the two contributions.

We studied the adsorption of deuterated myoglobin on PEG brushes with different degrees of polymerisation (N = 56, 146 and 770), and as a function of the area per grafted chain. The contribution of primary and ternary adsorption was separated for the different systems, and the adsorbed amount was extracted and the adsorption isotherms compared to the theoretical predictions. The ability to distinguish between the different adsorption modes, and the quantification of their relative contribution to the overall amount of adsorbed proteins, represents a major advance in optimising surface properties. In particular, the occurrence of ternary adsorption onto PEG brushes affects their status as tool for repressing protein adsorption.

L’adsorption de protéines aux interfaces a un rôle important pour certaines applications pharmaceutiques ou biotechnologiques. En effet, plusieurs processus indésirables sont liés à l’adsorption de protéines, par exemple l’encrassement de lentilles de contact, la coagulation dans des appareils contenant du sang, l’inflammation d’organes artificiels ou encore la diminution du temps de circulation dans le corps de protéines ou liposomes thérapeutiques. Certains polymères, tels que le polyéthylène glycol (PEG), sont utilisés pour réprimer l’adsorption de protéines :en greffant une brosse de PEG sur la surface, une couche est créée entre la protéine et celle-ci qui diminue, voire même réprime complètement l’adsorption. Comprendre le mécanisme qui entrave l’adsorption aux interfaces est un sujet de recherche actif, qui pourrait mener à des améliorations significatives dans la conception de biomatériaux.

À ce jour, la compréhension du mécanisme d’adsorption de protéines sur des brosses de polymère n’est pas claire. Les premiers modèles décrivant les interactions entre brosses de polymères et particules adsorbantes prédisaient deux modes d’adsorption :l’adsorption primaire sur la surface de greffage, et l’adsorption secondaire à l’extérieur de la brosse (pour les grandes protéines cylindriques uniquement). L’adsorption primaire peut-être réprimée en augmentant la densité de greffage de la brosse, et l’adsorption secondaire en augmentant son épaisseur, en accord avec les expériences reportées dans la littérature. Mais d’autres évidences expérimentales (un maximum dans la quantité adsorbée observé pour les brosses longues) ont ensuite suggéré l’existence d’un troisième mode :l’adsorption ternaire à l’intérieur même de la brosse, due aux interactions attractives entre la protéine et la brosse.

Les techniques standards peuvent en général mesurer la quantité adsorbée totale. Le but de ce travail était de séparer les isothermes d’adsorption primaire et ternaire, en utilisant la réflectivité de neutrons et des protéines deutérées. Comme les neutrons interagissent différemment avec les atomes d’hydrogène ou de deutérium, le contraste entre la brosse hydrogénée et la protéine deutérée est ainsi suffisant pour séparer les deux contributions.

Nous avons étudié l’adsorption de myoglobine deutérée sur des brosses de PEG avec différents degrés de polymérisation (N = 56, 146 and 770), en fonction de l’aire par chaîne Σ. La contribution des adsorptions primaire et ternaire put être séparée pour les différents systèmes, et les quantités adsorbées extraites pour finalement comparer les isothermes d’adsorption aux prédictions théoriques. La possibilité de distinguer les différents modes d’adsorption, et la quantification de leur contribution relative à la quantité totale de protéines adsorbées représente une avancée majeure dans l’optimisation des propriétés des surfaces. L’adsorption ternaire dans les brosses de PEG en particulier remet en question leur utilisation pour réprimer l’adsorption de protéines.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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17

Lankshear, Ethan Robert. "Covalently anchored polymerisation initiator monolayers for polymer brush growth." Thesis, University of Canterbury. Chemistry, 2015. http://hdl.handle.net/10092/10415.

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This thesis describes the covalent modification of carbon electrodes with a monolayer of polymerisation initiators and the growth of polymer brushes by surface initiated atom transfer radical polymerisation (SI-ATRP). Monolayer modification was sought to preserve the underlying electrode properties and topography and to produce a well-organised layer from which the polymer brushes can be grown. This work investigated two approaches for immobilising a monolayer of polymerisation initiators. Firstly, the electrochemical grafting of protected aryl diazonium salts produced a covalently anchored monolayer of tether groups that can participate in subsequent amide coupling and click reactions, to covalently anchor the polymerisation initiator. Secondly, specific reactions between the electrode surface and appropriate polymerisation initiator derivatives have been used to covalently anchor the initiators. For most systems, electro-active ferrocene (Fc) groups were reacted with modified surfaces as model reactants to enable the electrochemical estimation of the surface concentration of the polymer initiator groups. Film thickness measurements of the ethynylaryl (Ar-Eth) monolayer were carried out using atomic force microscopy confirming a monolayer. XPS analysis confirmed the presence of bromine on most of the polymerisation initiator modified samples. Modification of surfaces with polymer brushes can introduce new surface properties, such as switchable wettability, while maintaining the underlying bulk substrate properties. This work focused on examining SI-ATRP at each of the polymerisation initiator monolayers, with the aim to identify the most promising system(s) for further investigation. Polymer brushes of poly(3-(methacryloylamino)propyl)-N,N’-dimethyl(3-sulfopropyl)-ammonium hydroxide) (PMPDSAH) were grown from initiators tethered through the aryl diazonium salts modification procedure. Redox probe voltammetry and XPS analysis indicated that the grafting from polymerisation by the copper catalysed SI-ATRP was successful. Polymer brushes of poly(methyl methacrylate) PMMA were grown from the Ar-Eth modified monolayer by three SI-ATRP procedures: a standard procedure, an electrochemically mediated SI-ATRP method and a one-pot copper catalysed azide-alkyne click (CuAAC) reaction and SI-ATRP reaction from the Ar-Eth monolayer. Redox probe voltammetry and AFM images provided evidence for the growth of polymer brushes by these three methods. The successful one-pot CuAAC/SI-ATRP reaction for simultaneous coupling of the polymerisation initiator to the surface and polymerisation is a new approach for the production of polymer brushes and it minimises the number of surface modification steps needed. This method appears most promising for further development.
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18

Raynor, Jenny E. "Surface modification of titanium substrates with polymer brushes to control cell adhesion for bioapplications." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26653.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.
Committee Chair: Collard, David M.; Committee Co-Chair: Garcia, Andres J.; Committee Member: France, Stefan; Committee Member: Ragauskas, Arthur; Committee Member: Temenoff, Johnna. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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19

Schellkopf, Leonard. "Investigation of Polymer Systems in Solutions with Electron Microscopy and Scattering Methods." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-167948.

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This work is focused on the visualization and thus in the aid in finding explanations for the behavior of polymer structures as they exist in solution. For this aim, preparation and imaging techniques based on cryo-TEM protocols were developed for a large variety of polymeric specimens using new commercially available devices and the results were compared with the findings of other means of structural investigations. The systems used in this work were chosen, as their investigations can be adapted to other polymer systems by slight adaptation of the preparation procedures.
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20

Hamelinck, Paul Johan. "Functional surface-initiated polymers : device applications and polymerization techniques." Thesis, University of Cambridge, 2008. https://www.repository.cam.ac.uk/handle/1810/270327.

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Self-assembled monolayers and surface-initiated polymer, or polymer brushes, have attracted attention as they form dense layers with much higher structural order than bulk or solution polymers. Another field of research which has emerged over the last two decades is the field of organic and polymer electronics. In this field molecular order and surface modification are of major influence on the device performance, hence that both self-assembled monolayers as polymer brushes have been investigated to find applications in organic electronic devices. After an introduction into the field self-assembled monolayers, polymer brushes and organic electronics, the first part of this thesis focusses on three applications of surface modification techniques for applications in devices. Alignment of the active material is crucial for high mobilities in organic electronics. Chapter 2 discusses the synthesis of a liquid crystalline surface-initiated polymer and its application to induce strong homeotropic alignment. The alignment is homogeneous over large areas and can be patterned by combining the polymerization with soft lithographic techniques. Mobilities of organic electronic materials can also be strongly influenced by dopants in the material. In field-effect transistors the positioning of the dopant is thought to be crucial, as the conductance predominantly takes place in only a small channel near the dielectric interface. In chapter 3 dopant functionalized monolayers and polymer brushes are presented which enable the localized deposition of dopants in the channel of organic transistors. It is shown that the mobility of charges and hence the device performance is affected by the introduction of this dopant layer. Polymer brushes have been suggested for the fabrication of highly ordered semiconducting polymers. In chapter 4 the use of a thiophene functionalized polymer brush is shown, that can be used as a template for the subsequent growth of highly conjugated surface grafted polythiophene layers. Thick polythiophene layers are obtained, that are low in roughness and show photoluminescence and polychromism upon doping. The second part (chapter 5 and 6) of this thesis presents new techniques for surface polymerizations. It is attractive to investigate reduction of reactor volume for polymer brush growth. Chapter 5 discusses a method to achieve volume reduction by back-filling the superfluous volume with beads. It is found that this influences the polymerization kinetics significantly. The combined advantages of less volume and enhanced reaction speeds enable reduction of the total amount of monomer needed by up to 90%. Chapter 6 presents a controlled way to convert initiators for atom transfer radical polymerization into initiators for nitroxide mediated polymerization. In this way mixed polymer brushes and block co-polymer brushes become accessible. This combination makes it an attractive tool to fabricate complex polymer architectures. The technologies used in this thesis show that the synthesis of polymer brushes enable the fabrication of complex architectures without the wastes normally associated with surface-initiated polymers. Combined with several functionalized polymer brushes with properties that enhance order, influence mobility or serve as template for the growth of surface attached conjugated polymers this shows the high potential for the application of surface-initiated polymers in organic electronics.
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21

Chen, Hong. "Development of multi-functional polymeric biomaterials." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1490706379312092.

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22

Rodriguez, Loureiro Ignacio [Verfasser], Emanuel [Akademischer Betreuer] Schneck, Svetlana [Gutachter] Santer, and Olivier [Gutachter] Diat. "Structural characterization of single and interacting soft interfaces displaying brushes of synthetic or biomolecular polymers / Ignacio Rodriguez Loureiro ; Gutachter: Svetlana Santer, Olivier Diat ; Betreuer: Emanuel Schneck." Potsdam : Universität Potsdam, 2018. http://d-nb.info/121840440X/34.

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23

Edmondson, S. "Functional polymer brushes." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598765.

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Controlled, surface-initiated growth of poly (glycidyl methacrylate) (PGMA) polymer brushes and PGMA/poly (methyl methacrylate) (PMMA) copolymer brushes at room temperature by atom transfer radical polymerization (ATRP) is demonstrated from silicon surfaces using a trichlorosilane-functional initiator. A methanol-water mix was used as the solvent and the polymerization was controlled by using a mix of CuCl and CuBr2 with 2,2’-dipyridyl (bpy) as the ligand. These polymer films are analysed by ellipsometry, atomic force microscopy (AFM) and fourier transform infra-red spectroscopy (FTIR). The synthesis of PGMA and PGMA/PMMA copolymers in solution by ATRP is also demonstrated using a similar system, and these polymers are analysed by NMR and FTIR and the reactivity ratios determined. The ring-opening of PGMA brush epoxides groups by octylamine from solution, resulting in thickening and cross-linking of the polymer film, is studied. Nucleophilic ring-opening of PGMA is used as the basis of a novel adhesive system in which the brush film is reacted with a nucleophilic oxidized polydimethylsiloxane (PDMS) elastomer surface, forming an adhesive bond with a well-defined all-covalent link between the surfaces. Using PGMA/PMMA random copolymer brushes in this system allows a bond with atunable failure stress to be fabricated by varying the monomer ratio. By introducing UV-cleavable functionality into a surface initiating group on gold, possible routes towards an adhesive bond that can be weakened by the application of UV light are explored. By patterning thiol-functional ATRP initiators onto gold surfaces using microcontact printing and growing PGMA brushes only in these defined regions, “quasi-2D” polymers (objects with lateral dimensions much greater than the thickness) are fabricated.
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24

Chen, Tao, Ihsan Amin, and Rainer Jordan. "Patterned polymer brushes." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138928.

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This critical review summarizes recent developments in the fabrication of patterned polymer brushes. As top-down lithography reaches the length scale of a single macromolecule, the combination with the bottom-up synthesis of polymer brushes by surface-initiated polymerization becomes one main avenue to design new materials for nanotechnology. Recent developments in surface-initiated polymerizations are highlighted along with diverse strategies to create patterned polymer brushes on all length scales based on irradiation (photo- and interference lithography, electron-beam lithography), mechanical contact (scanning probe lithography, soft lithography, nanoimprinting lithography) and on surface forces (capillary force lithography, colloidal lithography, Langmuir–Blodgett lithography) (116 references)
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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25

Chen, Tao, Ihsan Amin, and Rainer Jordan. "Patterned polymer brushes." Royal Society of Chemistry, 2012. https://tud.qucosa.de/id/qucosa%3A27793.

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This critical review summarizes recent developments in the fabrication of patterned polymer brushes. As top-down lithography reaches the length scale of a single macromolecule, the combination with the bottom-up synthesis of polymer brushes by surface-initiated polymerization becomes one main avenue to design new materials for nanotechnology. Recent developments in surface-initiated polymerizations are highlighted along with diverse strategies to create patterned polymer brushes on all length scales based on irradiation (photo- and interference lithography, electron-beam lithography), mechanical contact (scanning probe lithography, soft lithography, nanoimprinting lithography) and on surface forces (capillary force lithography, colloidal lithography, Langmuir–Blodgett lithography) (116 references).
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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26

Mirous, Brian K. "SYNTHESIS AND PRESUMPTIVE CROSSLINKING OF STIMULI-RESPONSIVE DIBLOCK POLYMER BRUSHES." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1144783034.

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27

Scheibelein, Christoph [Verfasser]. "Mechanical Activation of Polymer Brushes and the Evolution of Stable Brush Architectures / Christoph Scheibelein." München : Verlag Dr. Hut, 2018. http://d-nb.info/1168535026/34.

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28

König, Meike. "Functional Coatings with Polymer Brushes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-126365.

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The scope of this work is to fathom different possibilities to create functional coatings with polymer brushes. The immobilization of nanoparticles and enzymes is investigated, as well as the affection of their properties by the stimuli-responsiveness of the brushes. Another aspect is the coating of 3D-nanostructures by polymer brushes and the investigation of the resulting functional properties of the hybrid material. The polymer brush coatings are characterized by a variety of microscopic and spectroscopic techniques, with a special emphasis on the establishment of the combinatorial quartz crystal microbalance/spectroscopic ellipsometry technique as a tool to characterize the functional properties of the polymer brush systems insitu. The pH-responsive swelling of the polyelectrolyte brushes poly(acrylic acid) and poly(2-vinylpyridine), as well as the thermoresponsive swelling of poly(N-isopropylacryl amide) is studied in detail by this technique. Poly(2-vinylpyridine) and binary poly(N-isopropylacryl amide)-poly (2-vinylpyridine) brushes are used as templates for the insitu-synthesis of palladium and platinum nanoparticles with catalytic activity. As an example for the use of polymer brushes to immobilize enzymes, the model enzyme glucose oxidase is physically adsorbed to poly (2-vinylpyridine) and poly (acrylic acid) brushes and also covalently bound to poly (acrylic acid) brushes. In the last part of this thesis, sculptured thin films are coated with poly (acrylic acid) and poly (N-isopropylacryl amide) brushes and the swelling characteristics as well as the adsorption behavior of the model protein bovine serum albumin are investigated.
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29

Roderick, Christopher. "Stability analysis of polymer brushes." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85644.

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The term polymer brush refers to the class of structures formed by polymers when attached to a surface at sufficiently high surface density so as to cause the polymers to stretch away from the surface to avoid each other. Considering specifically brushes formed by flexible, linear homopolymers attached by a single end to an impenetrable planar surface, this thesis investigates the stability of the laterally homogeneous phase of the brush in response to fluctuations of polymer density. The controlling factors studied are: the energetic interactions of the polymers with the bath of solvent particles in which the brush is immersed; the excluded volume of the polymers, which results from the mutual repulsion that exists between any two polymer segments; and the polymeric content in the brush, controlled by the grafting density and the length of the polymers. It is found that the stability of the laterally homogeneous phase of the brush is enhanced by increasing the polymer excluded volume, the polymeric content in the brush, or both. When incompressibility is modeled at the mean field level, it is found that there exists a region of parameter space in which the laterally homogeneous phase is stable for all values of the polymer-solvent interaction.
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30

Romeis, Dirk. "Conformational Transitions in Polymer Brushes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-139354.

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A polymer brush is formed by densely grafting the chain ends of polymers onto a surface. This tethering of the long macromolecules has considerable influence on the surface properties, which can be additionally modified by changing the environmental conditions. In this context it is of special interest to understand and control the behavior of the grafted layer and to create surfaces that display a desired response to external stimulation. The present work studies densely grafted polymer brushes and the effects that such an environment imposes on an individual chain molecule in the grafted layer. For this purpose we developed a new self-consistent field approach to describe mixtures of heterogeneous chains comprised of differently sized hard spheres. Applying this method to the case of polymer brushes we consider a fraction of grafted molecules to be different from the majority brush chains. The modification of these chains includes a variation in the degree of polymerization, a different solvent selectivity behavior and a variable size of the free end-monomer. Due to the computational efficiency of the present approach, as compared for example to direct simulation methods, we can study the conformations of the modified 'guest' chains systematically in dependence of the relevant parameters. With respect to brush profile and the distribution of the free chain ends the new method shows very good quantitative agreement with corresponding simulation results. We also confirm the observation that these 'guest' chains can undergo a conformational transition depending on the type of modification and the solvent quality. For the cases studied in the present work we analyze the conditions to achieve a most sensitive behavior of this conformational switching. In addition, an analytical model is proposed to describe this effect. We compare its predictions to the numerical results and find good agreement.
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31

Nkoua, Ngavouka Maryse Dadina. "Conformational properties of variable density DNA nanobrushes." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11129.

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2013/2014
Advanced nanotechnologies allow the manipulation of molecules with nanoscale precision, and can be used for the production of sensitive devices for protein or nucleic acids detection for clinical use. DNA nano-assemblies are an excellent route for ultrasensitive DNA/RNA detection and for DNA-protein conjugated immobilization, for bio interaction studies, through the careful detection of single strand DNA (ssDNA) hybridization with complementary target sequences. For DNA nanoscale devices, the control of DNA surface density and conformation is crucial in order to achieve the highest reproducibility and to optimize the sensitivity. An improved understanding of the chemical and physical properties of the nanoscale DNA assemblies and of the recognition process is necessary for device performance optimization. In this framework, we first focused on the understanding of the mechanisms that optimize and limit hybridization efficiency in variable density DNA monolayers. We performed Atomic Force Microscopy (AFM) assisted-Nanografting and AFM measurements to realize reference patches into a DNA self-assembled monolayer, and to carefully monitoring DNA hybridization. We then performed molecular dynamics (MD) simulations, in collaboration with a theoretical group, to capture the energetic hybridization limit in high dense DNA monolayers. We found that no more than 44% of the substrate ssDNA can be successfully hybridized, limited by molecular and electrostatic crowding effect connected to the highly charged nature of DNA. To further capture the conformational properties of DNA monolayers, and their relation to biorecognition, we characterized the ionic strength effect on ssDNA nano-assembled of different density by careful AFM topography measurements in liquid environment. We confined ssDNA brushes with controlled surface densities within a bio-repellent self-assembled monolayer. We then monitored the topographic brush height variation upon changing salt type (NaCl, KCl, CaCl2 and MgCl2 ) and concentration inside the liquid cell. We showed that the measured height is related to scaling law of salt concentration, in agreement with the theory of polyelectrolyte brush. Using this scaling model to fit our experimental data, we quantified structural parameters such as the average internucleotide distance (d) for ssDNA brushes of different, estimated surface density σ, featuring a strong dependence of d on different salts species. This result is crucial for the structural designing of synthetic nucleic acids and, more generally, nucleic acid-based devices with controlled physical behaviors. In the last part of the work, we apply all knowledge learned on hybridization mechanism to a clinical problem. We studied the hybridization mechanism to distinguish single base mismatch and to detect at high sensitivity, without any labeling and amplification, microRNAs (miRNAs) connected to hearth failure disease. Our results demonstrate that the AFM nanolithography can serve as a sensitive and selective readout system to discriminate single nucleotide polymorphism. Also, our device allows for the detection of more than one sequence of miRNAs on a same assay with target in picomolar (100pM) range concentration.
I recenti sviluppi delle nanotecnologie permettono di manipolare singole molecole con precisione nanometrica, e possono essere utilizzati per la produzione di dispositivi innovativi ad alta sensitivita` per la rivelazione di proteine e acidi nucleici, per usi clinici. Nanostrutture di DNA a singolo filamento rappresentano una eccellente soluzione per la rivelazione ultrasensibile di frammenti di DNA/RNA e per l’immobilizzazione di coniugati DNA-proteina per studi di bioriconoscimento, attaverso lo studio dell’ibridazione del DNA con le sequenze target complementari. Nello sviluppo di dipositivi alle nanoscale basati sul DNA, il controllo di parametri quali la densita` di superficie e la conformazione del DNA, risulta cruciale per raggiungere gli alti livelli di riproducibilita` richiesti e per ottimizzare la sensitivita`. Studiare e capire in dettaglio le proprieta` chimico -fisiche di strutture alle nanoscale di DNA a singolo filamento, e del relativo processo di bioriconoscimento risulta quindi fondamentale per ottimizzare le prestazioni del dispositivo associato. In questo contesto, ci siamo dapprima focalizzati sullo studio dei meccanismi che ottimizzano e limitano l’efficienza di ibridazione in monolayer di DNA. Usando il microscopio a forza atomica (AFM) e una tecnica di nanolitografia basata sull’AFM, il nanografting, abbiamo costruito delle nanostrutture di riferimento in film di DNA autoassemblati, ad alta densita`, ed abbiamo accuratamente monitorato con l’AFM e con simulazioni di dinamica molecolare, il limite di ibridazione in tali film. In collaborazione con un gruppo di fisici teorici, abbiamo trovato un limite di ibridazione pari a circa il 44% delle sequenze probe, collegandolo a effetti di repulsione elettrostatica dovuta all’ alta densita` a di carica nei monolayer di DNA, un polielettrolita altamente carico in soluzione. In un secondo tempo, per cogliere le proprieta` conformazionali dei monolayer di DNA, e la loro relazione con la capacita` di bioriconoscimento, abbiamo creato delle nanostrutture di DNA a singolo filamento, a densit variabile, in un monostrato autoassemblato di molecole bio-repellenti, e caratterizzato l’effetto della forza ionica della soluzione a mezzo di misure topografiche fatte con l’ AFM, in liquido. Da misure di variazione dell’ altezza topografica delle nanostrutture di DNA in funzione dei diversi sali usati in soluzione (NaCl, KCl, CaCl2 and MgCl2 ) e della loro concentrazione, abbiamo dimostrato che, per ogni sale, l’ altezza` legata alla concentrazione da una legge di scala, in accordo con la teoria dei polyelectrolyte brush. Utilizzando questa legge di scala, abbiamo fatto un fit dei dati sperimentali, quantificando un importante parametro strutturale, la distanza media tra nucleotidi nel filamento (d), per nanostrutture di DNA con divesra densita`, anch’essa stimata dal nostro fit. Questo risultato e` fondamentale per il disegno di acidi nucleici sintetici e piu` in generale per la progettazione di dispositivi miniaturizzati per la rivelazione di acidi nucleici. Nella parte finale di questo lavoro di tesi, abbiamo applicato le conoscenze acquisite sui meccanismi di ibridazione del DNA su scale nanometriche, per realizzare dispositivi utili a scopi clinici. Abbiamo studiato il meccanismo di ibridazione per distinguere un mismatch tra due filamenti complementari di DNA relativo a una singola base e alla rivelazione di micro-RNA, biomarcatori rilevanti per monitorare specifiche malattie quali, nel presente caso, malattie cardiovascolari. Abbiamo dimostrato che i nostri nanodispositivi dimostrano un’ottima risoluzione (100 pM o meglio) e che possono essere utilizzati senza bisogno di amplificazione del materiale genetico originale, o di altre modificazioni, in estratti provenienti da plasmi umani. Queste piattaforme possono essere ulteriormente sviluppate per il monitoraggio di polimorfismi di singolo nucleotide, estremamente rilevanti dal punto di vista clinico
XXVII Ciclo
1986
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32

Soga, K. Geoffrey (Kenneth Geoffrey). "Equilibrium phase separation in polymer brushes." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40445.

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The equilibrium properties of polymers end-grafted to an impenetrable interface, the "polymer brush", are investigated. Relevant concepts and techniques of statistical polymer physics are discussed; in particular, a simulation technique that is very efficient for studying polymer brushes is introduced. This technique is demonstrated through simulations of a well characterized polymer brush system. The results of original investigations of phase separation in polymer brushes are also presented. An instability in the lateral monomer density of a polymer brush is observed under sufficiently poor solvent conditions. The onset of this instability is found to agree with a previous prediction. A compositional instability is found in the lateral densities of a two-component polymer brush under conditions of sufficient immiscibility between the two components. The effects of varying solvent conditions are considered. Finally, the onset of the compositional instability is determined using the technique of the self consistent mean field, and the results compared to simulation.
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33

Nawroth, Jonas F., Claudia Neisser, Artur Erbe, and Rainer Jordan. "Nanopatterned polymer brushes by reactive writing." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-214281.

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Polymer brush patterns were prepared by a combination of electron beam induced damage in self-assembled monolayers (SAMs), creating a stable carbonaceous deposit, and consecutive self-initiated photografting and photopolymerization (SIPGP). This newly applied technique, reactive writing (RW), is investigated with 1H,1H,2H,2H-perfluorooctyltriethoxysilane SAM (PF-SAM) on silicon oxide, which, when modified by RW, can be selectively functionalized by SIPGP. With the monomer N,N-dimethylaminoethyl methacrylate (DMAEMA), we demonstrate the straightforward formation of polymer brush gradients and single polymer lines of sub-100 nm lateral dimensions, with high contrast to the PF-SAM background. The lithography parameters acceleration voltage, irradiation dose, beam current and dwell time were systematically varied to identify the optimal conditions for the maximum conversion of the SAM into a carbonaceous deposit. The results of this approach were compared to patterns prepared by carbon templating (CT) under analogous conditions, revealing a dwell time dependency, which differs from earlier reports. This new technique expands the range of CT by giving the opportunity to not only vary the chemistry of the created polymer patterns with monomer choice but also vary the chemistry of the surrounding substrate.
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34

Nawroth, Jonas F., Claudia Neisser, Artur Erbe, and Rainer Jordan. "Nanopatterned polymer brushes by reactive writing." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A29980.

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Polymer brush patterns were prepared by a combination of electron beam induced damage in self-assembled monolayers (SAMs), creating a stable carbonaceous deposit, and consecutive self-initiated photografting and photopolymerization (SIPGP). This newly applied technique, reactive writing (RW), is investigated with 1H,1H,2H,2H-perfluorooctyltriethoxysilane SAM (PF-SAM) on silicon oxide, which, when modified by RW, can be selectively functionalized by SIPGP. With the monomer N,N-dimethylaminoethyl methacrylate (DMAEMA), we demonstrate the straightforward formation of polymer brush gradients and single polymer lines of sub-100 nm lateral dimensions, with high contrast to the PF-SAM background. The lithography parameters acceleration voltage, irradiation dose, beam current and dwell time were systematically varied to identify the optimal conditions for the maximum conversion of the SAM into a carbonaceous deposit. The results of this approach were compared to patterns prepared by carbon templating (CT) under analogous conditions, revealing a dwell time dependency, which differs from earlier reports. This new technique expands the range of CT by giving the opportunity to not only vary the chemistry of the created polymer patterns with monomer choice but also vary the chemistry of the surrounding substrate.
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35

Lee, Thomas. "Tunable nanopatterns formed by polymer brushes." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10519.

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Tunable nanopatterns formed by polymer brushes A molecular dynamics simulation study of polymer brushes is presented. When exposed to a poor solvent, or when dried out in air, polymer brushes can undergo “constrained dewetting” and collapse into a nanopatterned layer. By changing the chemical environment of the polymer, the pattern can be switched on or off reversibly. Coarse-grained molecular dynamics was used to investigate the morphology and dynamics of these nanopatterns, and their influence on fluid flow and nanoparticle formation. Evaporation of a good solvent film from polymer brushes with a range of grafting densities was simulated in order to study the pattern morphology as a function of solvent content. The pattern type, dynamics, and size and number of features depended on the total amount of adsorbed material, including polymer and solvent. The result suggests the possibility for the use of polymer brushes as surfaces with reversibly tunable nanopatterns. Nonequilibrium molecular dynamics simulations were used to study the boundary condition of fluid flow over a polymer brush. In a good solvent the stagnation length for flow within the brush scaled with the chain spacing D as D-2/3, while the physical height scaled as D2. In a poor solvent the patterns formed by constrained dewetting created variations in the liquid velocity near the surface, suggesting a possible application as a switchable nanofluidic mixer. A simple model relates the boundary condition at the patterned surfaces to the height and polymer surface coverage. The patterns formed by constrained dewetting could be used as a template for surface nanoparticle formation to create surfaces with useful optical and electronic properties. Simulations showed that when a solution of molecular species was evaporated from a polymer brush, the constrained dewetting of the polymer could impart control over the nucleation of nanoparticles. The nanoparticle size and distribution depended on the concentration and solubility of the dissolved species.
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36

Kalan, Steven V. "Surface Modification of Silicon Through Thermal Annealing and Rinsing of Solvent Cast Polystyrene Films." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1316651768.

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37

Jia, Haidong. "Polymer brushes at nanoparticle and planar interfaces." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526480.

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38

Oren, Ron. "Probing the internal structure of polymer brushes." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611682.

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39

Galuschko, André. "Molecular dynamics simulations of sheared polymer brushes." Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/GALUSCHKO_Andre_2010.pdf.

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40

Bisen, Milind Dhaniram. "Synthesis and Characterization of Siloles, Silole-Containing Polymers and Photoswitchable Polymer Brush." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/990.

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In today's world, there is an increasing demand for new and efficient materials to develop future technologies, address the energy crisis, improve the health care system, and in general for the amelioration of our society. There has been substantial ongoing research effort to develop new organic materials for application in electronic devices and alternative energy such as solar cell, and to develop new biomaterials that will provide fast and efficient diagnosis and treatment of diseases. In this dissertation, we report our progress toward the development of new materials with potential for future application as organic electronics and biomaterials. The first part of this dissertation is focused on the method development and synthesis of silole-based small molecules and conjugated polymers. Silole, a silicon analogue of cyclopentadiene is a very interesting molecule due to its unique photo-physical and electronics properties, and a potential candidate for electroluminescent and photo-luminescent based applications. Although the first example of silole has been reported more than 25 year ago, the difficulty in the synthesis of functional siloles diminished the impact of their potential applications. Herein, we report an efficient and feasible synthetic method to synthesize 2,5-reactive siloles. We utilized this method to synthesize silole monomers, which will be applicable for various palladium catalyzed cross-coupling reactions. In cases where the preparation of reactively functionalized siloles were unsuccessful by our method, we were able to accomplish the synthesis in one additional step; nevertheless, our method is still advantageous compare to the other known methods. We have also synthesized silole molecules that can be further functionalized for application as fluorescent sensors. The synthesis and properties of new silole-containing conjugated polymers are described. The polymers were synthesized by the Suzuki, Sonogashira and Stille coupling polymerization. We have studied structure-property relationship of these polymers by exploring their optoelectrical properties. Co-polymers of silole with diketopyrrolopyrrole showed low band gap and low reduction potentials, which are crucial properties in developing n-type materials. We have also fabricated simple photovoltaic device to study photoconductivity, one of the silole-DPP polymer showed fairly high photoconversion efficiency but low current. Further characterization is required to study the conductivity. Silole-containing polymers were also prepared by the direct arylation reaction. The Direct Arylation reaction via C-H bond activation is emerging as a potential alternative to traditional transition metal-catalyzed cross-coupling reactions. We investigated synthetic methods to synthesize silole containing polymers via direct arylation polymerization by screening catalyst, ligand, solvent, temperature and other parameters. Our preliminary results demonstrated the successful copolymerization of 2,5-diarylhalide functionalized silole monomer with various electron accepting benzodiazole scaffolds to give alternating copolymers with low energy band gaps. However, the molecular weights were not optimal, and therefore future work is needed to optimize the reaction conditions in order to obtain higher molecular weight polymers. In the second part of this dissertation, we prepared photo-switchable polymer brush on silicon surfaces. Photoswitchable polymer brushes consisting of N-isopropylacrylamide and photoactive spiropyran moiety were synthesized by Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization method. These brushes reversibly react to external light stimulus by altering their polarity, ionic charge and solubility. In our preliminary study, we have shown that charged species can be adsorbed and release by the brushes with irradiation of UV and visible light, respectively. These polymer brushes can be used for isolation of charged protein/peptides.
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41

Khanduyeva, Natalya. "Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1232556562686-70575.

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The aim of the present work was to screen the main methods for the synthesis of conjugated polymers for their suitability in the preparation of conductive polymer brushes. The main focus was put on the grafting of intrinsically soluble substituted regioregular polyalkylthiophenes because of their excellent optoelectronic properties. The resulting polymer films were characterized and their optoelectrical properties studied. For the first time, a synthesis of conductive polymer brushes on solid substrates using “grafting-from” method was performed. The most important, from my opinion, finding of this work is that regioregular head-to-tail poly-3-alkylthiophenes – benchmark materials for organic electronics - can be now selectively grafted from appropriately-terminated surfaces to produce polymer brushes of otherwise soluble polymers - the architecture earlier accessible only in the case of non-conductive polymers. In particular, we developed a new method to grow P3ATs via Kumada Catalyst Transfer Polymerization (KCTP) of 2-bromo-5-chloromagnesio-3-alkylthiophene. Exposure of the initiator layers to monomer solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The obtained data suggests that the grafting process occurs not only at the poly(4-bromstyrene) (PS-Br)/polymerization solution interface, but also deeply inside the swollen PS-Br films, penetrable for the catalyst and for the monomer The grafting process was investigated in detail and the structure of the resulting composite film was elucidated using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Conductive atomic force microscopy (C-AFM). The obtained data suggests that the grafting process occurs not only at the poly(4-bromostyrene), PS-Br/polymerization solution interface, but also deeply inside the swollen PS-Br film, which is penetrable for the catalyst and the monomer. The process results in an interpenetrated PS-Br/P3HT network, in which relatively short poly(3-hexylthiophene), P3HT grafts emanate from long, cross-linked PS-Br chains. A further method investigated during our work was to covalently graft regioirregular P3HT to substrates modified by macromolecular anchors using oxidative polymerization of 3HT with FeCl3. P3HT layers with variable thicknesses from 30 nm up to 200 nm were produced using two steps of polymerization reaction. The P3HT obtained by oxidative polymerization had always an irregular structure, which was a result of the starting monomer being asymmetric, which is undesired for electronic applications. The third method for the production of conductive polymer brushes was to graft regioregular poly(3,3''-dioctyl-[2,2';5',2'']terthiophene) (PDOTT) by electrochemical oxidative polycondensation of symmetrically substituted 3,3''-dioctyl-[2,2';5',2'']terthiophene (DOTT). A modification of the supporting ITO electrode by the self-assembled monolayers (SAMs) of compounds having polymerizable head-groups with properly adjusted oxidative potentials was found to be essential to achieve a covalent attachment of PDOTT chains. The polymer films produced show solvatochromism and electrochromism, as well as the previous two methods. After polymerization, the next step towards building organic electronic devices is applying the methods obtained in nano- and microscale production. Block copolymers constitute an attractive option for such surface-engineering, due to their ability to form a variety of nanoscale ordered phase-separated structures. However, block copolymers containing conjugated blocks are less abundant compared to their non-conjugated counterparts. Additionally, their phase behaviour at surfaces is not always predictable. We demonstrated in this work, how surface structures of non-conductive block copolymers, such as P4VP-b-PS-I, can be converted into (semi)conductive P4VP-b-PS-graft-P3HT chains via a surface-initiated polymerization of P3HT (Kumada Catalyst Transfer Polymerization (KCTP) from reactive surface-grafted block copolymers. This proves that our method is applicable to develop structured brushes of conductive polymers. We believe that it can be further exploited for novel, stimuli-responsive materials, for the construction of sensors, or for building various opto-electronic devices. The methods developed here can in principle be adapted for the preparation of any conductive block copolymers and conductive polymers, including other interesting architectures of conductive polymers, such as block copolymers, cylindrical brushes, star-like polymers, etc. To this end, one needs to synthesize properly-designed and multi-functional Ni-initiators before performing the polycondensation.
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42

Khanduyeva, Natalya. "Conjugated Polymer Brushes (Poly(3-hexylthiophene) brushes): new electro- and photo-active molecular architectures." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23635.

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Abstract:
The aim of the present work was to screen the main methods for the synthesis of conjugated polymers for their suitability in the preparation of conductive polymer brushes. The main focus was put on the grafting of intrinsically soluble substituted regioregular polyalkylthiophenes because of their excellent optoelectronic properties. The resulting polymer films were characterized and their optoelectrical properties studied. For the first time, a synthesis of conductive polymer brushes on solid substrates using “grafting-from” method was performed. The most important, from my opinion, finding of this work is that regioregular head-to-tail poly-3-alkylthiophenes – benchmark materials for organic electronics - can be now selectively grafted from appropriately-terminated surfaces to produce polymer brushes of otherwise soluble polymers - the architecture earlier accessible only in the case of non-conductive polymers. In particular, we developed a new method to grow P3ATs via Kumada Catalyst Transfer Polymerization (KCTP) of 2-bromo-5-chloromagnesio-3-alkylthiophene. Exposure of the initiator layers to monomer solutions leads to selective chain-growth polycondensation of the monomers from the surface, resulting into P3AT brushes in a very economical way. The grafting process was investigated in detail and the structure of the resulting composite films was elucidated using several methods. The obtained data suggests that the grafting process occurs not only at the poly(4-bromstyrene) (PS-Br)/polymerization solution interface, but also deeply inside the swollen PS-Br films, penetrable for the catalyst and for the monomer The grafting process was investigated in detail and the structure of the resulting composite film was elucidated using ellipsometry, X-ray Photoelectron Spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and Conductive atomic force microscopy (C-AFM). The obtained data suggests that the grafting process occurs not only at the poly(4-bromostyrene), PS-Br/polymerization solution interface, but also deeply inside the swollen PS-Br film, which is penetrable for the catalyst and the monomer. The process results in an interpenetrated PS-Br/P3HT network, in which relatively short poly(3-hexylthiophene), P3HT grafts emanate from long, cross-linked PS-Br chains. A further method investigated during our work was to covalently graft regioirregular P3HT to substrates modified by macromolecular anchors using oxidative polymerization of 3HT with FeCl3. P3HT layers with variable thicknesses from 30 nm up to 200 nm were produced using two steps of polymerization reaction. The P3HT obtained by oxidative polymerization had always an irregular structure, which was a result of the starting monomer being asymmetric, which is undesired for electronic applications. The third method for the production of conductive polymer brushes was to graft regioregular poly(3,3''-dioctyl-[2,2';5',2'']terthiophene) (PDOTT) by electrochemical oxidative polycondensation of symmetrically substituted 3,3''-dioctyl-[2,2';5',2'']terthiophene (DOTT). A modification of the supporting ITO electrode by the self-assembled monolayers (SAMs) of compounds having polymerizable head-groups with properly adjusted oxidative potentials was found to be essential to achieve a covalent attachment of PDOTT chains. The polymer films produced show solvatochromism and electrochromism, as well as the previous two methods. After polymerization, the next step towards building organic electronic devices is applying the methods obtained in nano- and microscale production. Block copolymers constitute an attractive option for such surface-engineering, due to their ability to form a variety of nanoscale ordered phase-separated structures. However, block copolymers containing conjugated blocks are less abundant compared to their non-conjugated counterparts. Additionally, their phase behaviour at surfaces is not always predictable. We demonstrated in this work, how surface structures of non-conductive block copolymers, such as P4VP-b-PS-I, can be converted into (semi)conductive P4VP-b-PS-graft-P3HT chains via a surface-initiated polymerization of P3HT (Kumada Catalyst Transfer Polymerization (KCTP) from reactive surface-grafted block copolymers. This proves that our method is applicable to develop structured brushes of conductive polymers. We believe that it can be further exploited for novel, stimuli-responsive materials, for the construction of sensors, or for building various opto-electronic devices. The methods developed here can in principle be adapted for the preparation of any conductive block copolymers and conductive polymers, including other interesting architectures of conductive polymers, such as block copolymers, cylindrical brushes, star-like polymers, etc. To this end, one needs to synthesize properly-designed and multi-functional Ni-initiators before performing the polycondensation.
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43

Wilshaw, Claire Tamsin. "Directed phase separation of polymer blends on binary-patterned polymer brushes." Thesis, University of Sheffield, 2009. http://etheses.whiterose.ac.uk/573/.

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Self-assembly of well-defined polymer microstructures is of interest for applications such as polymer solar cells, light emitting diodes, microelectronics and biosensors. Chemically patterned substrates can direct the phase separation of thin films of polymer blends, producing controlled morphologies. This has been demonstrated using patterned self-assembled monolayers. Binary-patterned polymer brushes provide a robust, chemically and topographically patterned surface which can interact with the blend, potentially resulting in interesting new behaviour, and greater control over phase separation. Binary-patterned polystyrene/poly(methyl methacrylate) brushes were synthesised by a novel method. A self-assembled monolayer of triethoxysilane was patterned by exposure to ultraviolet light. This produced amine-terminated areas that could react with 2-bromoisobutyryl bromide to produce initiators for atom transfer radical polymerisation, allowing the synthesis of patterned polymer brushes. Dehalogenation of the first brush, followed by deprotection, modification and a second polymerisation produced binary-patterned brushes. Unpatterned and patterned polymer brushes were characterised using ellipsometry, x-ray photoelectron spectroscopy, contact angles, atomic force microscopy, lateral force microscopy, optical microscopy and secondary ion mass spectrometry. An alternative approach, based on direct microcontact printing of an atom transfer radical polymerisation initiator, 11-(2-bromo-2-methyl)propionyloxyundecyltrichlorosilane, was also investigated, although this approach was ultimately unsuccessful. The behaviour of thin films of polystyrene/poly(methyl methacrylate) blends on silicon, patterned self-assembled monolayers and binary-patterned polymer brushes was studied. The morphologies were investigated using atomic force microscopy, optical microscopy, nuclear reaction analysis and secondary ion mass spectrometry, in order to determine the effect of the binary-patterned polymer brushes on the domain structure of the blend. The blend morphology was complex and reflected interactions between the blend and the brushes (as well as other factors). When the natural length scale of the blend is commensurate with the underlying pattern, phase separation may be spatially directed by the substrate.
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44

Van, Velzen Vera. "Enhancing the functionality of hydrogels using molecular polymer brushes." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/226153/1/Vera_Van%20Velzen_Thesis.pdf.

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This thesis studies a new approach to enhance the properties of hydrogels using Molecular Polymer Brushes (MPB’S). It examines the morphology of the MPB’s and the GelMA-MPB’s network, the effect of the brushes on the mechanical properties of the hydrogel and the effect of the brushes on the encapsulated cells. In doing so, a new hydrogel is developed, providing new possibilities in the field of cartilage regeneration with the potential to improve treatment for Osteoarthritis.
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45

Gupta, Smrati. "Immobilization of Inorganic Nanoparticles on Responsive Polymer Brushes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1222086844714-55891.

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Exploitation of well defined responsive polymer brushes for direct and controlled immobilization of metal/semiconductor nanoparticles on macroscopic surfaces has been demonstrated. The employed approach offers the possibility of the organization of a variety of inorganic nanoparticles by irreversible bonding and homogenous distribution on an underlying substrate. The immobilization process has been realized by chemical grafting of a variety of polymer brushes on a suitable substrate followed by the attachment of pre-/in-situ formed nanoparticles exploiting the chemical/physical interactions between surface functionalities of nanoparticles and polymer chain segments. A number of polymer brushes including poly (acrylic acid), polystyrene, poly (2-vinyl pyridine) and poly (N-isopropyl acrylamide) brushes have been prepared on silicon substrate by the “grafting to” approach. A variety of inorganic nanoparticles such as quantum dots (CdTe) noble metals (gold and silver) and magnetic (Fe3O4) were immobilized on macroscopic surfaces to impart them photo luminescent, catalytic or magnetic properties. In addition, responsiveness of grafted polymer brushes in terms of variation in thickness (due to changes in chain conformation) as a function of external stimuli such as solvent and pH allowed to use the resulting polymer brush-nanoparticles nanoassemblies in the fabrication of nanosensors. The design of fabricated nanosensors is based on the modulation in the interparticle distance of immobilized nanoparticles due to swelling/deswelling of underlined polymer brushes in response to some external trigger.
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46

Chen, Meng. "Synthesis and properties of surface-grown polymer brushes." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443606.

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47

Rigby, Matthew. "A friction study of densely grafted polymer brushes." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123065.

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This thesis outlines the development of a new method for friction force measurements using atomic force microscopy. It is compared to the standard friction force microscopy technique for verification. This new method is used to investigate the friction properties in the boundary lubrication regime of a novel polymer brush sample with a very high grafting density. It is found that there is no correlation between friction coefficient and the surrounding fluid's pH or salt concentration, and that the coefficient of friction is on the order of 0.1.
La présente thèse aborde le développement d'une nouvelle méthode pour les mesures de friction à l'aide d'un microscope à force atomique. Elle est comparée à la méthode standard pour vérification. Cette nouvelle méthode est utilisée afin d'investiguer les propriétés dans le régime de la limite de lubrification d'un nouvel échantillon de brosse de polymères à très haute densité. Aucune corrélation n'a été trouvé entre le coefficient de friction et le pH ou la concentration de sel du fluide environnant. Le coefficient de friction mesuré est de l'ordre de 0.1.
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48

Pelras, Theophile Werner Louis. "Nanostructured Soft Matter from Compartmentalised Molecular Polymer Brushes." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/21150.

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Abstract:
Polymer science is rapidly advancing towards the precise construction of synthetic macromolecules of formidable complexity. The impressive advances in control over polymer composition, topology and uniformity, enabled by the living polymerisation revolution, now permit the introduction of compartmentalisation within macromolecules. Despite the straightforward and versatile synthetic approaches to produce block copolymer, nanostructures built-up from these linear building-blocks rarely reaches dimensions beyond the 5–50 nm range and can be sensitive to their environment. The development of robust controlled polymerisation techniques has enabled the synthesis of covalently-bond polymer architectures that can be used as nano-scale building-blocks. One of these architectures are molecular polymer brushes (also known as bottlebrush polymers or cylindrical polymer brushes). Molecular polymer brushes (MPBs) are unique materials that possess astonishing properties arising from their densely grafted and extended chain structure. The field of MPBs, especially as compartmentalised entities, is rapidly growing. Recent efforts have focussed on achieving MPBs with programmed complexity and the introduction of orthogonal chemical functionality. Compartmentalised brushes can elevate their functionality beyond that of their linear constituent parts, thus offering immense potential in self-assembly and template chemistry. The aim of this thesis is to demonstrate how the compartmentalisation in MPBs can be used for the construction of complex, yet precise, polymer nano- and microstructures with the scope to develop advanced functional materials.
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49

Wu, Zhenghao. "Investigating the Effects of Grafting and Chain Stiffness on Nanoconfined Polymers from Molecular Dynamics Simulation." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525861929889197.

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50

Pardo-Figuerez, Maria M. "Designing neuronal networks with chemically modified substrates : an improved approach to conventional in vitro neural systems." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/27941.

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Abstract:
Highly organised structures have been well-known to be part of the complex neuronal network presented in the nervous system, where thousands of neuronal connections are arranged to give rise to critical physiological functions. Conventional in vitro culture methods are useful to represent simplistic neuronal behaviour, however, the lack of such organisation results in random and uncontrolled neurite spreading, leading to a lack of cell directionality and in turn, resulting in inaccurate neuronal in vitro models. Neurons are highly specialised cells, known to be greatly dependent on interactions with their surroundings. Therefore, when surface material is modified, drastic changes in neuronal behaviour can be achieved. The use of chemically modified surfaces in vitro has opened new avenues in cell culture, where the chaotic environment found in conventional culture methods can be controlled by the combination of surface modification methods with surface engineering techniques. Polymer brushes and self-assembled monolayers (SAMs) display a wide range of advantages as a surface modification tool for cell culture applications, since their properties can be finely tuned to promote or inhibit cellular adhesion, differentiation and proliferation. Therefore, when precisely combined with patterning techniques, a control over neuronal behaviour can be achieved. Neuronal patterning presents a system with instructive cues that can be used to study neuron-neuron communication by directing single neurites in specific locations to initiate synapses. Furthermore, although this area has not been much explored, the use of these patterned brushes could also be used in co-culture systems as a platform to closely monitor cell heterotypical communication. This research demonstrates the behaviour of SH-SY5Y neurons on a variety of SAMs and polymer brushes, both in isolation and combination to promote cellular spatial control. APTES and BIBB coatings promoted the highest cell viability, proliferation, metabolic activity and neuronal maturation, whilst low cell adhesion was seen on PKSPMA and PMETAC surfaces. Thereafter, PKSPMA brushes were used as a potential cell repulsive coating and its combination with micro- patterning techniques (photolithography and soft lithography) resulted in a system with instructive cues for neuronal guidance, where neuronal directionality was obtained. In the final chapter of this thesis, a chimeric co-culture system was developed where the patterned SH-SY5Y cells were co-cultured with C2C12 myoblasts in an attempt to obtain an organised neuronal-muscle co-culture system. Whilst preliminary observations showed first stages of a patterned neuronal-muscle co-culture, future work is necessary to refine and improve the patterned co-culture process.
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