Hydrogels based on alkylated chitosan and polyelectrolyte copolymers

Hydrogels formed by alkylated chitosan with N‐(3‐chloro‐2‐hydroxypropyl) trimethylammonium chloride and synthetic copolymers forming polyelectrolyte complexes are presented. The copolymer polyelectrolytes were synthesized through free‐radical polymerization. Their compositions and reactivity parameters were determined by the Finemann–Ross and Kelen–Tüdos methods. The copolymers have structures that tend to be alternating. The hydrogels were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, scanning electron microscopy, and water solubility tests at different pH values. For the formation of the hydrogels, they were prepared using different molar ratios of alkylated chitosan and polyelectrolyte copolymers. Their stability was determined by rheological analysis, evaluating the response as a function of strain and frequency. The rheological tests showed that the stability of the polyelectrolyte complexes followed the trend ChT‐CP2 > ChT‐CP3 > ChT‐CP1 due to the presence of greater electrostatic interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46556.     

Hydrogels based on graft copolymers of collagen synthesis

Graft copolymerization of 2-hydroxyethyl methacrylate in combination with hydrophobic monomers onto soluble collagen was employed in the synthesis of hydrogels. The hydrogels were formed by simultaneous graft copolymerization and crosslinking. In order to study the effect of various crosslinking agents on the water retention character of the hydrogels, three different crosslinking agents, namely, N,N′-methylene bis acrylamide, 1,4-butanediol dimethacrylate, and hexamethylene urethanediacrylate were used. Hexamethylene urethanediacrylate crosslinked systems require a minimum amount of crosslinking agent to attain maximum water content in comparison to the other systems.     

Hydrogels prepared from polysiloxane chains by end linking them with trifunctional silanes containing hydrophilic groups

A strongly hydrophobic polymer was converted into a hydrogel by introducing hydrophilic side chains of sufficient lengths and amounts to overcome the hydrophobicity but sufficiently well dispersed to avoid disadvantages such as loss of the transparency required in applications. Specifically, poly(dimethylsiloxane) (PDMS) hydrogels were successfully prepared by end linking a combination of long and short chains to give the bimodal distributions of network chain lengths that generally give unusually good mechanical properties. The end linkers were chosen using trialkoxylsilanes R′Si(OR)₃ having R′ side chains that are hydrophilic of variable lengths and of sufficient hydrophilicity to produce the desired hydrogels. The first trialkoxysilane was N-(triethoxysilylpropyl)-O-polyethylene oxide urethane (S1) with 4–6 units of ethylene glycol, and the second was [methyoxy(polyethyleneoxy)propyl]-trimethoxysilane (S2) with 6–9 units of ethylene glycol, and they were used to end link hydroxyl-terminated PDMS chains in standard room-temperature condensation reactions. It was possible to introduce the hydrophilic side chains into the hydrophobic networks without discernible phase separation. These linear side chains increase equilibrium water contents, from 0 to 11.2 wt% in the first series and from 0 to 29.8 wt% in the second. Longer hydrophilic chains clearly migrated to the surfaces of the resulting PDMS hydrogels to give reduction in static contact angles from 105° to 40° for the first series, and to 80° for the second. The longer hydrophilic chains were found to give larger decreases in the contact angles and larger equilibrium water contents. The mechanical properties demonstrated that Young's moduli of the hydrogels did not change upon introduction of the S1 hydrophilic cross linker, but did decrease from the presence of the S2. The tensile strength and elongation at break were relatively insensitive to the amounts of either of the hydrophilic groups.     

The influence of side-chain and main-chain spacer lengths on the thermal and structural properties of diethanolamine based side-chain polyesters

Summary A series of linear side-chain aliphatic polyesters have been synthesized from -(bis(2-hydroxyethyl)amino)--(4-methoxybiphenyl-4-oxy) alkanes and aliphatic acid chlorides. The side-chain and main-chain spacer lengths were varied and their influences on thermal and structural properties of polyesters, as determined by DSC and X-ray diffraction, are discussed.     

Chemically amplified resists based on polymer side-chain rearrangement or electrophilic crosslinking

A variety of resist systems have been studied that owe their sensitivity to the occurrence of catalyzed electrophilic rearrangements or substitution processes. In most designs, polyfunctional or polymer-bound benzylic ethers, esters, or alcohols are used in the key step of the reaction, which is initiated by protonation of the latent electrophilic moiety, resulting in formation of a carbocationic center. Thermal activation of the electrophilic process leads to the formation of new C–C bonds with liberation of a proton; therefore the overall process is catalytic and amounts to chemical amplification. A variety of polymers and active small molecules that provide access to both negative and positive tone images have been tested, and sensitivities as high as 0.1 mJ/cm² have been measured. In addition, several image reversal schemes involving either selective silylation of non-exposed areas or the in situ photogeneration of base have been tested and are presented.     

Hydrogen-bond induced side-chain liquid crystalline polymers based on nicotinic acid derivatives

Supramolecular side-chain liquid crystalline poly(acrylate)s have been prepared by self-assembly of H-bond donor and acceptor complexes through intermolecular complementary hydrogen bond formation. Poly[4-(m-acryloyloxyalkyloxy)benzoic acid]s [m = 6 (P1) and 8 (P2)] were employed as polymer components. Liquid crystalline nicotinic acid derivatives (C1, C2, C3, and C4) were used as complementary H-bond donor/acceptor counterparts. The liquid crystalline properties of the nicotinic acid derivatives, the polymers and their complexes were investigated by DSC and POM. Methylene spacers present at the terminal position of the nicotinic acid derivatives played a key role in mesophase arrangements. The columnar phase exhibited by the nicotinic acid derivatives completely disappeared in the H-bonded complexes to afford a nematic phase, thereby substantiating the complex formation.     

Dynamic mechanical and shape memory properties of polybenzoxazines based on aminopropyl‐terminated siloxanes

Four siloxane‐containing benzoxazine monomers and telechelic benzoxazine oligomers were synthesized from 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane, α,ω‐bis(3‐aminopropyl)polydimethylsiloxane, phenol, o‐allylphenol, and formaldehyde. The length of the siloxane segment affects the polymerization reaction of the benzoxazine monomers and telechelic benzoxazine oligomers. The dynamic mechanical properties of the corresponding polybenzoxazines depend primarily on the structure of phenol and the length of the siloxane segment. The polybenzoxazines exhibit one‐way dual‐shape memory behavior in response to changes in temperature. The thermally induced shape memory effects of the polybenzoxazines were characterized by bending and tensile stress–strain tests with a temperature program based on their glass transition temperatures. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44121.     

Designing the hydrophobic core of Thermus flavus malate dehydrogenase based on side-chain packing

We have developed a computational method for the de novo design ofhydrophobic cores of proteins and tested it experimentally. The method iscomposed of a pair of programs, (i) to optimize side-chain conformationsusing an updated rotamer library for potential hydrophobic residues, basedon the backbone structure of the protein of interest, and (ii) to estimatechanges in Gibbs free energies between the folded and unfolded structuresof the optimized sequence. Using these programs, we have engineered severalvariants of Thermus flavus malate dehydrogenase. To quantitate thestability change in each variant, the circular dichroism spectra of theproteins were measured as a function of guanidine hydrochlorideconcentration and deltadeltaG(H2O) values of the proteins were determinedby extrapolation of the experimental data. However, variants with doublereplacements showed different denaturation cooperativity from that of thewild type and therefore it was difficult to simply compare the theoreticaland experimental stability of each variant using calculated deltadeltaG andexperimental deltadeltaG(H2O) values. When the calculated deltadeltaGvalues were compared with those at 3.5 M guanidine hydrochloride, which wasthe transition midpoint obtained from the denaturation curve of the wildtype, good correlation was observed.     

Organic phase PPO biosensor based on hydrophilic films of electropolymerized polypyrrole

We described herein, the construction of an organic phase enzyme electrode (OPEE) via polyphenol oxidase (PPO) entrapment within a hydrophilic polypyrrole film electrogenerated from on a new bispyrrolic derivative (1) containing a long hydrophilic spacer. The so-called “adsorption step procedure” was adopted for the preparation of the organic phase PPO biosensor. The amperometric detection of catechol was carried out in anhydrous chloroform at −0.2 V versus Ag/AgCl. The electroanalytical parameters of the biosensor strongly depend on its configuration and on the hydration state of the enzyme matrix. The best sensitivity obtained for catechol in chloroform was 15.6 mA M⁻¹ cm⁻².     

Molecular packing and phase transitions of side-chain liquid crystalline polymethacrylates based on p-methoxyazobenzene

The phase structures and transition behaviors of a series of side-chain liquid crystalline (LC) polymethacrylates based on p-methoxyazobenzene (PMnAzs, n = 6, 8, 10, 12) were studied using differential scanning calorimetry, one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction, and Fourier transform infrared spectroscopic experiments. The LC phase transition of PMnAz follows the sequence of smectic A (SmA) ? nematic (N) ? isotropic (I). For PM10Az and PM12Az, the transition of SmA-to-N is not complete upon heating. In the low-temperature SmA phase, the polymers adopt a fully interdigitated side-chain packing with the smectic layer period almost identical to the side-chain length. For all the four samples, the first-order diffraction of the SmA structure only renders when the temperature approaches the transition of SmA ? N, with the intensity much lower than that of the second-order diffraction. The absence of the first-order diffraction at low temperatures is ascribed to the possible matching of the electron densities between the center portion of the side-chain sublayer and the main-chain sublayer of the SmA structure. Since only the mesogens from the same main-chain sublayer can stack parallel together, the distribution of the azobenzene domains may cause some sort of density undulation within the smectic layer. Among the samples, PM6Az presents the strongest undulation with some additional orders. We also examined the annealing effect on the H-aggregation of PMnAzs. It is found that isothermal annealing at a temperature slightly higher than the T_g of PM8Az and PM10Az can significantly enhance the UV absorption at 326 nm, indicating a further development of H-aggregation. However, for PM6Az and PM12Az, the UV–vis spectrum of the annealed sample is nearly identical to that without annealing.     

Hydrogels for biomedical use based on 1-vinyl-2-pyrrolidone crosslinked with macromonomers

Macromonomers of various chain lengths with an average of three allyl double bonds per chain were prepared by anionic copolymerization of allyl methacrylate with methyl methacrylate. The macromonomers were characterized by gel permeation chromatography and nuclear magnetic resonance. The macromonomers were then copolymerized with 1-vinyl-2-pyrrolidone to form three-dimensional structures. Their optical, swelling and mechanical properties were studied and the crosslinking efficiency was determined. The copolymer properties are not greatly affected by macromonomer chain lengths up to 40-mers; above 50-mers there is a slight decrease in the equilibrium water content and a significant increase in the modulus of elasticity. The crosslinking efficiency depends on the macromonomer chain length; a marked increase was observed for the 50-mer because of a greater number of methyl-methyl interactions. Copolymers have favourable strength-strain properties and a low content of water-soluble extracts, in which the IR analysis demonstrated the presence of 1-vinyl-2-pyrrolidone homopolymers. In spite of the good results obtained for all the macromonomers described in this work, the 50-mer seems to be optimal for copolymerization with 1-vinyl-2-pyrrolidone.     

Hydrogels based on polyurethane–polyacrylic acid multiblock copolymers via macroiniferter technique

Polyurethane (PU)–polyacrylic acid (PAAc) multiblock copolymers have been prepared via a macroiniferter technique, and were tested for living mechanism, thermal, and water swell of the cast films. It was found that molecular weight of the PU–PAAc block copolymers linearly increased while molecular weight distribution decreased with conversion. As the PAAc content increases, water swell of the cast films and crystalline melting temperature (T_m) of PU decreased while glass transition temperature of PU increased.     

基于重组蛋白质的水凝胶

基于重组蛋白质的水凝胶在生物医学领域有广泛的潜在应用,因此这一领域在近20年吸引了研究工作者的极大研究热情并取得了巨大的进展。在这篇综述中,我们简要地讨论了基于重组蛋白质的水凝胶领域的最新进展,所涵盖的内容包括以生物识别为驱动力的物理交联的水凝胶以及化学交联的水凝胶的设计和构筑,以及它们在生物医学领域的应用。同时我们也讨论这一进展迅速的生物材料领域的发展前景与方向。     

含木质素水凝胶的研究进展

综述了含木质素水凝胶的研究概况。含木质素水凝胶主要由三种方式制备:木质素或改性木质素直接交联;木质素与亲水性单体接枝,同时加交联剂交联;木质素以互穿或半互穿的形式引入水凝胶中。向水凝胶中引入木质素,可以使凝胶具有pH敏感和溶剂敏感性,或者使其具备吸附与富集金属离子的功能,或者改变温度敏感型水凝胶的最低临界溶解温度。     

Hot-melt pressure-sensitive adhesives based on SIS-g-PB copolymer for transdermal delivery of hydrophilic drugs

SIS-g-PB copolymers were successfully synthesized by grafting living polybutadiene (PB) lithium macroanions onto epoxidized SIS copolymers. Their molecular structures and thermal properties were characterized by TGA, ¹H-NMR and DSC, respectively. SIS, epoxidized SIS (ESIS) and SIS-g-PB copolymers were melt-blended with tackifiers to develop hot-melt pressure-sensitive adhesives (HMPSAs), respectively (named of H-SIS, H-ESIS and H-SIS-g-PB). Their adhesive performances were measured in terms of 180° peel strength and holding power. A modified Franz type horizontal diffusion cell was used to carry out In vitro drug release experiments, in which geniposides were chosen as hydrophilic model drugs. The results showed that H-SIS-g-PB has two times as high a 180° peel strength as H-SIS. Meanwhile H-SIS-g-PB has a slightly lower drug cumulative release rate than H-ESIS. It is indicated that the PB branches not only could impart good adhesive performance to H-SIS-g-PB via improving the compatibility between the epoxidized main chains and tackifier resins but also provide release channels to hydrophilic drugs by retaining most of the epoxide groups in the SIS-g-PB copolymers.     

Composite gel electrolytes based on poly(methylmethacrylate) and hydrophilic fumed silica

Transparent and highly conducting (10⁻³ S cm⁻¹) composite gel electrolytes (cges) based on poly(methylmethacrylate) (PMMA) with 1 M LiClO₄ in propylene carbonate (PC) and hydrophilic fumed silica (SiO₂) added in different proportions up to 5 wt.% as the constituents were prepared. The unique property of the aggregates of surface hydroxyl groups of hydrophilic fumed silica to link together through hydrogen bonding to form a network and the interactions between various constituents, probed by FTIR spectroscopic technique, have revealed to control both the transport and rheological properties of the cges. The high mechanical and electrochemical stability of these cges makes them potential candidates as electrolytes in “All Solid State Electrochromic Windows” (ECWs). Detailed room temperature conductivity and viscosity measurements correlated to FTIR spectroscopic analysis of cges along with their optical and electrochemical investigations is reported in the present paper.     

Hydrogels based on N-isopropylacrylamide and methacrylic acid: thermal stability and glass transition behaviour

Summary The thermal stability and glass transition behaviour of crosslinked poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], their random copolymers and sequential interpenetrating polymer networks (IPNs) have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). P(MAA) shows a two-step process of degradation. P(N-iPAAm) shows an unique process of degradation at higher temperature. Copolymers having higher content in N-iPAAm units have a lower thermal stability than their component homopolymers and show an unique degradation process at high temperature. On the contrary, enriched MAA copolymers show better stability but they exhibit two degradation steps at the main degradation region. Sequential IPN samples exhibit a better stability than their component homopolymers and copolymers. The high temperature backbone degradation occurs in only one step, which indicates the formation of a true interpenetrating network. The T _g of the same series of materials has been also measured. A T _g vs composition plot of P(N-iPAAm-co-MAA) copolymers presents a S-shaped curve indicating that structural units interact among them through strong specific interactions. For interpenetrating polymer networks, it seems that only one T _g occurs indicating a good compatibility and interpenetration. Received: 1 December 2001 /Revised version: 12 February 2002/ Accepted: 12 February 2002     

Synthesis and properties of highly hydrophilic polyurethane based on diisocyanate with ether group

Highly hydrophilic polyurethane elastomers (PUEs) were synthesized from 1,2-bis(isocyanate) ethoxyethane (TEGDI), poly(ethylene oxide-co-propylene oxide) copolyol (EOPO) and 1,4-butane diol/1,1,1-trimethylol propane (75/25) (wt/wt) by a prepolymer method. 4,4′-Diphenylmethane diisocyanate (MDI)-based PUEs were synthesized as a control as well. Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) measurements revealed that the degree of microphase separation of the TEGDI-based PUEs was much weaker than for the MDI-based PUEs. Young's modulus and elongation at break of the TEGDI-based PUEs were quite lower and larger than for the MDI-based PUEs, respectively. This is due to quite weak cohesion force of the hard segment chains in the TEGDI-based PUEs. The degree of swelling of the TEGDI-based PUEs was five times larger than for the MDI-based one. This is associated with the hydrophilic nature of TEGDI and weak cohesion force in the TEGDI-based PUEs.     

Synthesis of siloxanes containing reactive side chains

The synthesis and characterization of siloxanes containing methacrylate, epoxy, and amino side chains are described. Direct hydrosilylation of unsaturated methacrylate or epoxy compounds with methyl hydrogen siloxanes resulted in the attachment of methacrylate or epoxy groups as side chains on the siloxane in good yields. Amino side chains on siloxanes were formed by acidic hydrolysis of the ketenimine side chains, obtained by hydrosilylation of unsaturated ketenimines with methyl hydrogen siloxanes. Details of the preparation and characterization of such unsaturated ketenimines are reported.This paper is from the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.