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Статті в журналах з теми "Ionic cross-Linking":
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Raak, Norbert, Lars Leonhardt, Harald Rohm, and Doris Jaros. "Size Modulation of Enzymatically Cross-Linked Sodium Caseinate Nanoparticles via Ionic Strength Variation Affects the Properties of Acid-Induced Gels." Dairy 2, no. 1 (March 8, 2021): 148–64. http://dx.doi.org/10.3390/dairy2010014.
Анотація:
Enzymatic cross-linking by microbial transglutaminase is a prominent approach to modify the structure and techno-functional properties of food proteins such as casein. However, some of the factors that influence structure-function-interrelations are still unknown. In this study, the size of cross-linked sodium caseinate nanoparticles was modulated by varying the ionic milieu during incubation with the enzyme. As was revealed by size exclusion chromatography, cross-linking at higher ionic strength resulted in larger casein particles. These formed acid-induced gels with higher stiffness and lower susceptibility to forced syneresis compared to those where the same number of ions was added after the cross-linking process. The results show that variations of the ionic milieu during enzymatic cross-linking of casein can be helpful to obtain specific modifications of its molecular structure and certain techno-functional properties. Such knowledge is crucial for the design of protein ingredients with targeted structure and techno-functionality.
2
Xia, Lin, Jiafeng Meng, Yuan Ma, and Ping Zhao. "Facile Fabrication of Eucommia Rubber Composites with High Shape Memory Performance." Polymers 13, no. 20 (October 11, 2021): 3479. http://dx.doi.org/10.3390/polym13203479.
Анотація:
We processed a series of shape memory Eucommia rubber (ER) composites with both carbon–carbon and ionic cross-linking networks via a chemical cross-linking method. The influence of the carbon–carbon cross-linking and ion cross-linking degree of ER composites on curing, mechanical, thermal, and shape memory properties were studied by DSC, DMA, and other analytical techniques. Dicumyl peroxide (DCP) and zinc dimethacrylate (ZDMA) played a key role in preparing ER composites with a double cross-linking structure, where DCP initiated polymerization of ZDMA, and grafted ZDMA onto polymer molecular chains and cross-linked rubber molecular chains. Meanwhile, ZDMA combined with rubber macromolecules to build ionic cross-linking bonds in composites under the action of DCP and reinforced the ER composites. The result showed that the coexistence of these two cross-linking networks provide a sufficient restoring force for deformation of shape memory composites. The addition of ZDMA not only improved the mechanical properties of materials, but also significantly enhanced shape memory performance of composites. In particular, Eucommia rubber composites exhibited outstanding mechanical properties and shape memory performance when DCP content was 0.2 phr.
3
Li, Lin, and Jin Kuk Kim. "THERMOREVERSIBLE CROSS-LINKING MALEIC ANHYDRIDE GRAFTED CHLOROBUTYL RUBBER WITH HYDROGEN BONDS (COMBINED WITH IONIC INTERACTIONS)." Rubber Chemistry and Technology 87, no. 3 (September 1, 2014): 459–70. http://dx.doi.org/10.5254/rct.14.86976.
Анотація:
ABSTRACT Thermoreversible cross-linking polymers are designed based on reversible cross-linking bonds. These bonds are able to reversibly dissociate and associate upon the input of external energy, such as heat or light. Reprocessibility is possible for this kind of material. The objective was to thermoreversibly cross-link maleic anhydride grafted chlorobutyl rubber (MAH-g-CIIR) via a reaction with octadecylamine, with an excess to obtain amide-salts, which form both hydrogen bonds and ionic interactions. X-ray diffraction experiments showed the presence of microphase-separated aggregates that acted as physical cross-links for both the MAH-g-CIIR precursor and amide-salts. The tensile properties were improved by converting MAH-g-CIIR to amide-salts, because of the combination of hydrogen bonding and ionic interactions. The cross-linked materials could be repeatedly compression molded at 155 °C into homogeneous films. The differential scanning calorimetry curves and Fourier transform infrared spectra indicate that hydrogen bonds are of a thermoreversible nature, but the recovery of ionic bonds is impossible. After treatment with heating-cooling for up to three cycles, the tensile strength of the thermoreversible cross-linking CIIR was greatly reduced. The gradual reduction in the effectiveness of the ionic-hydrogen bonds is the major contribution to the reprocessibility of these materials.
4
Wang, Wei, Shu Ping Liu, Hua Nan Guan, Jin Zhong Liang та Chong Tan. "Dye Adsorbent Prepared by Crosslinking of Poly(γ-glutamic acid) and Gelatin". Advanced Materials Research 989-994 (липень 2014): 809–13. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.809.
Анотація:
The present paper describes the preparation of novel biodegradable adsorbent based on cross-linking of poly (γ-glutamic acid) (γ-PGA) and gelatin and characterization of its Rhodamine B dye adsorption capability. Cross-linking effect was measured with the effect of adsorbent adsorbing ionic dyes Rhodamine B. In the experiment, the various factors which had influence on the adsorption effect, including preparationtemperature, preparation pH value, concentrations of cross-linking agent, cross-linking time were analyzed. The results showed that the adsorbent had good adsorption performance after cross-linking. The adsorbent was characterized by fourier transform infrared spectrum (FTIR), revealing that there were amide bonds between gelatin and poly (γ-glutamic acid) by cross-linking reaction.
5
Deng, Weina, Weiming Liu, Hai Zhu, Liang Chen, Haiyang Liao, and Han Chen. "Click-chemistry and ionic cross-linking induced double cross-linking ionogel electrolyte for flexible lithium-ion batteries." Journal of Energy Storage 72 (November 2023): 108509. http://dx.doi.org/10.1016/j.est.2023.108509.
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Yao, Song Kun, Qiu Jin Li, Wei Zhang, Ji Xian Gong, and Jian Fei Zhang. "Ionic Liquid-Regenerated Cellulose Beads as Solid Support Matrices for Papain Immobilization." Advanced Materials Research 535-537 (June 2012): 2349–52. http://dx.doi.org/10.4028/www.scientific.net/amr.535-537.2349.
Анотація:
A beads based on cellulose and the room temperature ionic liquid 1-butyl-3-methyl imidazolium chloride ([Bmim]Cl) was prepared. Regenerated cellulose beads were modified with silane, and characterized by scanning electron microscopy. Papain was immobilized on the beads used two different methods including glutaraldehyde and covalent cross-linking method. The immobilized enzyme activity of bead was determinated by BAEE (N-benzoyl- DL-arginine ethyl ester hydrochloride) determination. According to the enzyme activity and immobilization rate compared with covalent cross-linking method, glutaraldehyde cross-linking method is more suitable for amino-modified.
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Shim, Youngseon, Munbo Shim, and Dae Sin Kim. "A Computer Simulation Study of Thermal and Mechanical Properties of Poly(Ionic Liquid)s." Membranes 12, no. 5 (April 21, 2022): 450. http://dx.doi.org/10.3390/membranes12050450.
Анотація:
Thermal and mechanical properties of poly(ionic liquid)s (PILs), an epoxidized ionic liquid-amine network, are studied via molecular dynamics simulations. The poly(ionic liquid)s are designed with two different ionic liquid monomers, 3-[2-(Oxiran-2-yl)ethyl]-1-{4-[(2-oxiran-2-yl)ethoxy]phenyl}imidazolium (EIM2) and 1-{4-[2-(Oxiran-2-yl)ethyl]phenyl}-3-{4-[2-(oxiran-2-yl)ethoxy]benzyl}imidazolium (EIM1), each of which is networked with tris(2-aminoethyl)amine, paired with different anions, bis(trifluoromethanesulfonyl)imide (TFSI−) and chloride (Cl−). We investigate how ionic liquid monomers with high ionic strength affect structures of the cross-linked polymer networks and their thermomechanical properties such as glass transition temperature (Tg) and elastic moduli, varying the degree of cross-linking. Strong electrostatic interactions between the cationic polymer backbone and anions build up their strong structures of which the strength depends on their molecular structures and anion size. As the anion size decreases from TFSI− to Cl−, both Tg and elastic moduli of the PIL increase due to stronger electrostatic interactions present between their ionic moieties, making it favorable for the PIL to organize with stronger bindings. Compared to the EIM2 monomer, the EIM1 monomers and TFSI− ions generate a PIL with higher Tg and elastic moduli. This attributes to the less flexible structure of the EIM1 monomer for the chain rotation, in which steric hindrance by ring moieties in the EIM1-based PIL enhances their structural rigidity. The π-π stacking structures between the rings are found to increase in EIM1-based PIL compared to the EIM2-based one, which becomes stronger with smaller Cl− ion rather than TFSI−. The effect of the degree of the cross-linking on thermal and mechanical properties is also examined. As the degree of cross-linking decreases from 100% to 60%, Tg also decreases by a factor of 10–20%, where the difference among the given PILs becomes decreased with a lower degree of cross-linking. Both the Young’s (E) and shear (G) moduli of all the PILs decrease with degree of cross-linking, which the reduction is more significant for the PIL generated with EIM2 monomers. Transport properties of anions in PILs are also studied. Anions are almost immobilized globally with very small structural fluctuations, in which Cl− presents lower diffusivity by a factor of ~2 compared to TFSI− due to their stronger binding to the cationic polymer backbone.
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Ebrahimi, Mohammad, Kateryna Fatyeyeva, and Wojciech Kujawski. "Different Approaches for the Preparation of Composite Ionic Liquid-Based Membranes for Proton Exchange Membrane Fuel Cell Applications—Recent Advancements." Membranes 13, no. 6 (June 11, 2023): 593. http://dx.doi.org/10.3390/membranes13060593.
Анотація:
The use of ionic liquid-based membranes as polymer electrolyte membranes for fuel cell applications increases significantly due to the major features of ionic liquids (i.e., high thermal stability and ion conductivity, non-volatility, and non-flammability). In general, there are three major methods to introduce ionic liquids into the polymer membrane, such as incorporating ionic liquid into a polymer solution, impregnating the polymer with ionic liquid, and cross-linking. The incorporation of ionic liquids into a polymer solution is the most common method, owing to easy operation of process and quick membrane formation. However, the prepared composite membranes suffer from a reduction in mechanical stability and ionic liquid leakage. While mechanical stability may be enhanced by the membrane’s impregnation with ionic liquid, ionic liquid leaching is still the main drawback of this method. The presence of covalent bonds between ionic liquids and polymer chains during the cross-linking reaction can decrease the ionic liquid release. Cross-linked membranes reveal more stable proton conductivity, although a decrease in ionic mobility can be noticed. In the present work, the main approaches for ionic liquid introduction into the polymer film are presented in detail, and the recently obtained results (2019–2023) are discussed in correlation with the composite membrane structure. In addition, some promising new methods (i.e., layer-by-layer self-assembly, vacuum-assisted flocculation, spin coating, and freeze drying) are described.
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Percival, Stephen J., Leo J. Small, Erik D. Spoerke, and Susan B. Rempe. "Polyelectrolyte layer-by-layer deposition on nanoporous supports for ion selective membranes." RSC Advances 8, no. 57 (2018): 32992–99. http://dx.doi.org/10.1039/c8ra05580g.
Анотація:
This work demonstrates that the ionic selectivity and ionic conductivity of nanoporous membranes can be controlled independently via layer-by-layer (LbL) deposition of polyelectrolytes and subsequent selective cross-linking of these polymer layers.
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Zhong, Ming, Yi-Tao Liu, and Xu-Ming Xie. "Self-healable, super tough graphene oxide–poly(acrylic acid) nanocomposite hydrogels facilitated by dual cross-linking effects through dynamic ionic interactions." Journal of Materials Chemistry B 3, no. 19 (2015): 4001–8. http://dx.doi.org/10.1039/c5tb00075k.
Дисертації з теми "Ionic cross-Linking":
1
Forbey, Scott. "Design and Characterization of Electrospun Mats with Tailored Morphologies for Enhanced Active Layer Performance in Energy Conversion and Energy Storage Applications." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/52627.
Анотація:
The goal of this research was to utilize the morphological control inherently imparted by the electrospinning process to improve the active layer performance in energy conversion devices as well as to better understand the relationship between morphology and performance in energy storage devices. Discrete control of the active layer morphology can promote exciton dissociation in organic photovoltaic cells (OPVs), whereas developing efficient ion diffusion pathways and beneficial polymer-ion interaction in polymer-gel electrolytes is demonstrated to result in enhanced battery performance.
We demonstrate the ability to develop unique morphologies in Poly(3-hexafluoro propylene) (P3HT) films with energy storage applications using various electrospinning techniques. Electrospinning in a solvent-saturated atmosphere allows for the design of ribbon architectures with polymer domains on the order of 5-10 um. These ribbon structures form what appear to be bi-continuous films, which could then be filled with an acceptor / fullerene type material to create a bulk heterojucton for OPV devices. Dropping chloroform onto the electrospinning needle during the spinning process results in P3HT fibers with porous surfaces. These fibers have diameters of ~ 2 um. Using a coaxial needle to electrospin a P3HT solution in the core, and a CHCl3 sheath solution created hybrid ribbon-fiber structures. These structures have even smaller domain sizes than the ribbons created using a solvent saturated atmosphere. Cospinning P3HT with sacrificial polymers results in P3HT fiber morphologies upon removal of the sacrificial template polymer. Additionally, introducing P3HT into an established fiber matrix results in fibrous P3HT architectures after the template fibers are removed.
Developing hybrid polymer-gel electrolytes using crosslinked PEO electrospun fibers results in membranes with high affinity for liquid electrolyte components. These electrospun PEO fiber mats exhibit excellent ionic conductivities at room temperature (12 mS/cm) exceeding an electrospun PVDF control. Furthermore, the PEO fiber mats can absorb nearly three times as much liquid electrolyte as the PVDF control. PEO has been show to interact with lithium salts to aid in dissociation and diffusion during battery cycling. Although the ionic conductivity data suggest PEO to be a superior electrolyte, pulsed-field-gradient NMR shows that lithium diffusion is faster in PVDF samples. From coin cell discharge experiments, PEO is believed to interact strongly with Li+ ions, inhibiting them from diffusing rapidly during fast charge/discharge rates. However, PEO/PETA fiber electrolytes show nearly 100% theoretical capacity discharge at C/100 and a capacity retention of ~ 35% at a C/5 discharge rate in contrast to a glass fiber separator which shows only a capacity that is approximately 85% of the theoretical value.
The unique mechanical properties of PEO/PETA electrospun mats could lead to interesting artificial skin and wound healing applications. Upon crosslinking at elevated temperatures (~40 degrees C), the fiber mats exhibit improved tensile strength and much higher ultimate stress at break. The porous nature of the materials lend to easy oxygen diffusion for wound healing, and the hydrophilicity promotes continued adhesion to existing tissue making these mats possible adhesive-less bandages.Ph. D.
2
Young, Thomas. "Dépôts micro structurés pour la réalisation de capteurs d’activité hydrolytique." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN062.
Анотація:
La phytase, une enzyme capable d'hydrolyser séquentiellement l'acide phytique en formant des inositols moins phosphorylés et du phosphate, est de plus en plus souvent ajoutée aux régimes alimentaires des animaux afin d'optimiser l'absorption du phosphore par les animaux monogastriques et de réduire sa présence dans les fèces et les sols. À cet égard, la possibilité de mesurer son activité est évidemment d'un intérêt primordial. Cependant, à ce jour, il existe très peu de méthodes permettant de mesurer facilement l'activité de la phytase dans l'industrie. Les principales raisons sont que les techniques actuelles sont chronophages, ne sont pas adaptées aux échantillons d'aliments complexes et utilisent des réactifs dangereux.Dans ce projet de thèse, nous avons proposé de développer un capteur enzymatique innovant dédié à la détection de l'activité de la phytase dans des échantillons complexes en utilisant une méthode de détection directe grâce à la technologie de Zymoptiq. L'acide phytique, substrat de la phytase, possède de nombreuses charges négatives qui peuvent interagir avec des polymères chargés positivement comme le chitosan pour former des complexes. Ce phénomène est bien connu et documenté dans la littérature et constitue la pierre angulaire de notre capteur. Notre capteur est basé sur la dégradation de micro dépôts basés sur une structure en réseau de chaînes de chitosan insensibles à l'enzyme et réticulées avec de l'acide phytique lorsqu'ils sont incubés en présence d'activité phytase (FTU/mL).Cependant, pour assurer la stabilité du micro dépôt, une étude systématique a été menée pour mieux contrôler et comprendre tous les phénomènes sous-jacents liés à son assemblage. Cela a aussi permis d'améliorer la sensibilité du capteur développé. Grâce à des versions intermédiaires, nous avons démontré la capacité de notre méthode à mesurer l'activité d'un échantillon de phytase pure de 100 FTU/mL et d'un échantillon d'aliment complexe simulé avec des activités aussi faibles que 20 mFTU/mL. Enfin, après avoir caractérisé le mécanisme d'hydrolyse de l'acide phytique complexé avec le chitosan par la phytase, cette étude nous a permis de proposer une méthode de mesure innovante, sûre et rapidePhytase, an enzyme capable of sequential hydrolysis of phytic acid to lower phosphorylated inositols and phosphate, has been increasingly added to animal diets to optimize phosphorus uptake by monogastric animals and to reduce its presence in faeces and soils. In this respect, the ability to measure its activity is obviously of primary interest. However, to date there are very few methods available to easily measure phytase activity in industry. The main reasons are that current techniques are time consuming, not suitable for complex feed samples and use hazardous reagents.In this thesis project, we proposed to develop an innovative enzymatic sensor dedicated to the detection of phytase activities in complex samples using a label-free approach thanks to Zymoptiq's technology. Phytic acid, the substrate of phytase, possesses numerous negative charges that can interact with positively charged polymers such as chitosan to form complexes. This phenomenon is well known and documented in the literature and is the cornerstone of our sensor. Our sensor is based on the degradation of micro deposits-based on a network structure of enzyme-insensitive chitosan chains cross-linked with phytic acid- when incubated in the presence of phytase activity (FTU/mL).However, to ensure the stability of the micro deposit, a systematic study was carried out to better control and understand all the underlying phenomena related to the complexes assembly. This also allows us to tailor our sensor's sensitivity. Through intermediate versions, we have demonstrated the ability to measure the activity of both a pure phytase sample of 100 FTU/mL and a simulated complex feed sample with activities as low as 20 mFTU/mL. Finally, after characterizing the hydrolysis mechanism of phytic acid complexed with chitosan by phytase, this study has enabled us to propose an innovative, safe and time-saving method of measurement
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Lin, Shu-Tsung, and 林樹宗. "Metal Ionic Cross-Linking Reactions of Aqueous-Based Hybridized PU / Epoxy Resin." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/07062629586452678581.
Анотація:
碩士淡江大學
化學學系
88
A water-reducible epoxy resin is prepared by introducing a carboxylic acid onto epoxy resin via a half-esterification of maleic anhydride with hydroxyl group of epoxy resin.An amino-terminated aqueous-based PU dispersion is blended with this water-reducible epoxy resin and result in the formation of hybridized resins comprised carboxyl groups.These polymer carboxyl groups chelate with various metallic ions (such as Cu , Fe , Zn , Ca and etc.) and form a metallic ion cross-linked polymer.The metallic ion extaction is carried out either by polymer films or hybridized resin is depended on temperature,pH value of the solution.The resulted metallic ion cross-linked hybridized polymer are evaluated by the measurements of gel content, water-uptake, alcohol swollen, tensile strength, thermogravimetric analyais dynamic mechanical thermal analysis and etc.
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Lu, Yali. "Ionic cross-linking reagents and tandem mass spectrometry for mapping structures of proteins and protein complexes." Diss., 2008. http://proquest.umi.com/pqdweb?did=1631170231&sid=1&Fmt=2&clientId=3552&RQT=309&VName=PQD.
Частини книг з теми "Ionic cross-Linking":
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Yu, J. R., Y. Zuo, and Y. B. Xiong. "CHAPTER 7. Thermo-responsive Poly(ionic liquid) Nanogels Prepared via One-step Cross-linking Copolymerization." In Polymerized Ionic Liquids, 202–24. Cambridge: Royal Society of Chemistry, 2017. http://dx.doi.org/10.1039/9781788010535-00202.
2
Askari, Vahid Reza, Ramin Roshani, Hooman Hatami, and Vafa Baradaran Rahimi. "Fundamentals and applications of ionic biopolymers." In Ionotropic Cross-Linking of Biopolymers, 33–61. Elsevier, 2024. http://dx.doi.org/10.1016/b978-0-323-96116-5.00021-1.
3
Will, Cindy L., Berthold Kastner, and Reinhard Lührmann. "Analysis of ribonucleoprotein interactions." In RNA Processing, 141–77. Oxford University PressOxford, 1994. http://dx.doi.org/10.1093/oso/9780199633449.003.0005.
Анотація:
Abstract Elucidation of the precise function of small ribonucleoprotein particles (snRNPs) in RNA processing will be greatly aided by information regarding their biochemical composition and higher order structure. To date, significant biochemical and structural information has been gathered for the mammalian spliceosomal snRNPs Ul, U2, U5, and U4/U6, although their characterization is far from complete. The snRNA component of these functionally important RNP particles has been shown to be evolutionarily conserved and, with the exception of U6, possesses a unique 5’ cap structure, namely 2,2,7-trimethylguanosine (m3G). The spliceosomal snRNPs share a set of eight common proteins (referred to as B, B’ , Dl, D2, D3, E, F, and G) which are tightly associated with the snRNA component of the snRNP (1). Particle-specific proteins are also associated with several snRNP species (Ul, U2, U5, and the tri-snRNP [U4/U6.U5] complex), although in many cases their interaction is highly dependent on the ionic strength of the particle’ s environment (1). For this reason, the sedimentation coefficient of an individual snRNP may vary. At intermediate salt concentrations (approximately 0.3-0.5 M), Ul, U2, and U4/U6 sediment as 12S particles and U5 as a 20S particle, whereas at lower ionic strengths, a 17S U2 and a 25S [U4/U6.U5] tri-snRNP particle are also observed. Investigation of intermolecular interactions within RNP particles can be accomplished by a variety of procedures. Since most structural studies are facilitated by the analysis of individual RNP complexes in the absence of contaminating macromolecules, this chapter starts by describing the approaches commonly used for the isolation of snRNP particles. Several procedures are then described which are particularly useful for analysing RNA-protein interactions and/or RNP higher order structure. These include snRNP reconstitution, immunoprecipitation, RNA-protein cross-linking, nuclease protection, and immunoelectron microscopy.
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Erman, Burak, and James E. Mark. "Networks Having Multimodal Chain-Length Distributions." In Structures and Properties of Rubberlike Networks. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195082371.003.0015.
Анотація:
As was mentioned in chapter 10, end-linking reactions can be used to make networks of known structures, including those having unusual chain-length distributions. One of the uses of networks having a bimodal distribution is to clarify the dependence of ultimate properties on non-Gaussian effects arising from limited-chain extensibility, as was already pointed out. The following chapter provides more detail on this application, and others. In fact, the effect of network chain-length distribution, is one aspect of rubberlike elasticity that has not been studied very much until recently, because of two primary reasons. On the experimental side, the cross-linking techniques traditionally used to prepare the network structures required for rubberlike elasticity have been random, uncontrolled processes, as was mentioned in chapter 10. Examples are vulcanization (addition of sulfur), peroxide thermolysis (free-radical couplings), and high-energy radiation (free-radical and ionic reactions). All of these techniques are random in the sense that the number of cross-links thus introduced is not known directly, and two units close together in space are joined irrespective of their locations along the chain trajectories. The resulting network chain-length distribution is unimodal and probably very broad. On the theoretical side, it has turned out to be convenient, and even necessary, to assume a distribution of chain lengths that is not only unimodal, but monodisperse! There are a number of reasons for developing techniques to determine or, even better, control network chain-length distributions. One is to check the “weakest link” theory for elastomer rupture, which states that a typical elastomeric network consists of chains with a broad distribution of lengths, and that the shortest of these chains are the “culprits” in causing rupture. This is attributed to the very limited extensibility associated with their shortness that is thought to cause them to break at relatively small deformations and then act as rupture nuclei. Another reason is to determine whether control of chain-length distribution can be used to maximize the ultimate properties of an elastomer. As was described in chapter 10, a variety of model networks can be prepared using the new synthetic techniques that closely control the placements of crosslinks in a network structure.
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Shahinpoor, Mohsen. "Review of the use of Fibrous Contractile Ionic Polyacrylonitrile (PAN) in Smart Materials and Artificial Muscles." In Fundamentals of Smart Materials, 46–63. The Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/bk9781782626459-00046.
Анотація:
Chapter 5 reviews contractile ionic polyacrylonitrile (PAN) fibers as smart materials and artificial muscles. PAN fibers in an active form (PAN or PAN gel modified by annealing/cross-linking and partial hydrolysis) elongate and contract when immersed in pH solutions (caustic and acidic solutions, respectively). Activated PAN fibers can also contract and expand in polyelectrolyte when electrically and ionically activated with cations and anions, respectively. The change in length of these pH-activated fibers is typically greater than 100%. However, more than 900% contraction/expansion of PAN nanofibers (less than 1 micron in diameter) has been observed in the laboratories. PAN muscles present great potential as artificial muscles for linear actuation. The basic unit of commercially available PAN fibers (Mitsubishi Rayon Co., Japan, Orlon or artificial silk) that can be handled properly from an engineering point-of-view is a “single strand”. One PAN strand consists of approximately two thousand filaments. The typical diameter of each filament is approximately 10 μm in the raw state and 30 μm in the fully elongated state (gel). The advantages of PAN fibers among other electrolyte gels are that PAN fiber gels have good mechanical properties, which can be compared to those of mammalian biological muscles. The large volume change of PAN fiber gels also allows the reduction in the size of the gel, which is an important factor in determining the response time. PAN fibers can convert chemical energy directly into mechanical motion. Based on ion diffusion theory, the response time of swelling will be proportional to the square of the gel fiber diameter. Surface/volume ratio also affects the response time. Note that such pH-induced contraction–expansion of modified PAN fibers can also be induced electrically in a chemical cell by electrolysis and production of H+ and OH− ions.
Тези доповідей конференцій з теми "Ionic cross-Linking":
1
Cortes, Daniel H., Woojin M. Han, Lachlan J. Smith, and Dawn M. Elliott. "Extra-Fibrilar Matrix Properties of Human Annulus Fibrosus are Location and Age Dependent." In ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80536.
Анотація:
Aging and degeneration of the intervertebral discs are cell mediated processes that include biochemical, mechanical and structural changes. Although these processes are similar, disc degeneration is defined as an accelerated aging process that results in a detriment in the function of the disc. Biochemical changes include protein cross-linking, proteoglycan depletion and changes on collagen type. These compositional changes are related to changes in the mechanical properties of the disc and its tissues. For instance, it has been shown that an increase of protein cross-linking by glycation or genipin treatment causes an increase of the stiffness in disc tissues [1,2]. On the other hand, a decrease on the amount of proteoglycan has been shown to cause a decrease on tissue stiffness due to a reduction of the osmotic pressure [3,4]. However, during aging and degeneration, these two processes occur simultaneously with opposing effects on the mechanical properties of the tissue. Consequently, it is important to analyze these effects separately. Additionally, many multiphasic models for soft charged tissues, such articular cartilage and intervertebral disc, also consider the ionic phases separately from non-charged solids. Although multiphasic models for the disc have been used in the past, the mechanical properties of the non-charged extra-fibrillar matrix (EFM) have not been measured directly.