Preparation and characterization of molecularly imprinted polymer of bovine serum albumin

Molecularly imprinted polymer beads of bovine serum albumin (BSA) were prepared via inverse phase suspension polymerization, using BSA as the template molecule, a combination of acrylamide and methacrylic acid (MAA) as double functional monomers, and N, N′‐methylene bisacrylamide as the crosslinker. The effect of different monomer ratios and degrees of crosslinking were investigated. When both selectivity and physical properties of the resultant polymer beads were taken into account, the ratio of MAA in the total monomers was chosen at 40% (m/m) and the degree of crosslinking at 30% (n/n), the resultant polymer beads had good selectivity (α = 2.77) and good physical properties. The effects of pH and temperature were studied. It turned out that the functionalization of polymers of BSA prepared via inverse‐phase suspension polymerization exhibited specific recognition for BSA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A facile and efficient method for preparation of chiral supported poly(styrene–divinylbenzene) copolymers

A new and efficient method for preparation of optically active poly(styrene–divinylbenzene) copolymers (PS-DVB) is presented here. This is carried out by Friedel–Crafts acylation reaction of chiral N-phthaloyl -leucine acid chloride with PS-DVB beads in the presence of aluminum chloride as Lewis acid catalyst and 1,2-dichloroethane as the solvent at ambient temperature. Reagents’ amounts and reaction conditions are mentioned and four samples with different amounts of functionality have been prepared. Final products were characterized by FT-IR and elemental analysis. The results obtained confirm that the above modification in preparation of chiral supported PS-DVB has been achieved well and in moderate yield.     

Effect of method of preparation on properties of temperature and pH-sensitive gels: Chemical crosslinking versus irradiation with e-beam

Two problems that have impeded a broader application of polyelectrolytic smart polymers are their low speed of response and their faulty behavior in the presence of salts. To contribute to the solution of those problems we prepared two series of gels based on N-isopropylacrylamide (NIPAAm) containing ampholytic units using chemical crosslinking methods and electron beam irradiation. In the first method, the gels prepared contain NIPAAm, N-N′-dimethylaminoethylmethacrylate (DMAEM) and a methacrylate of the ortho-, meta- or para-benzoic acid, respectively, to impart amphoteric behavior. They were crosslinked using N-N′-methylenebisacrylamide (BIS) as crosslinker by standard free-radical techniques. In the second method aqueous solutions containing mixtures of polyNIPAAm and charge balanced copolymers of DMAEM with the methacrylates of the ortho-, meta- and para-benzoic acid, respectively, prepared previously, were irradiated by e-beam. Both series were characterized by DSC, mechanical compression and swelling–shrinking tests in deionized water, buffers solutions at different pH-values and in water having different salt concentrations. The results show that the gels prepared by irradiation have a swelling degree up to four times higher than that of the gels prepared by chemical crosslinking, furthermore, their shrinking velocity is up to twenty times higher than that of gels prepared by chemical crosslinking. The results also showed that the gels prepared by chemical crosslinking using monomers show only polyelectrolyte behavior, while those prepared by e-beam irradiation of polymer solutions show in fact amphoteric behavior; while all gels retained their temperature sensitivity between 32 and 39 °C.     

Hydrophilic polymer supports grafted by poly(ethylene glycol) derivatives via atom transfer radical polymerization

In this study, a newly structured hydrophilic polymer supports are prepared by the chemical modification (grafting) of the polystyrene-based preformed beads via atom transfer radical polymerization (ATRP) employing the CuBr/PMDETA catalyst system. Hydrophilic monomers including N,N-dimethylacrylamide (DMA) and poly(ethylene glycol) (PEG) macromonomers were grafted onto Merrifield type resin. Based on optical microscopic data, the particle sizes of the resins were increased in the order of 10 μm after the polymerization. This increment indicated that monomers are grafted not only to the particle surface but also to within a polymer matrix. These resins demonstrate well-swellability in polar solvent, and they enable high functional loadings up to 0.7-1.8 mmol g⁻¹. The high loading capacity in polar solvents and favorable mechanical properties of resins render them to have great potential applications in peptide and oligonucletide syntheses.     

Functionalization of crosslinked polystyrene by radiation-induced grafting

γ-ray irradiated beads of poly(styrene-divinylbenzene) (PS-DVB) have been graft copoly-merized with polyacrylic acid. Preirradiated PS-DVB beads were refluxed with acrylic acid in water, benzene, or toluene. Percentage of grafting was studied under various reaction parameters like total dose, reaction time, and molar concentration. Effects of reaction media, temperature of reaction, and presence of Mohr salt on the percentage of grafting were also studied. From the swelling property of PS-DVB beads in DMF and dichloro-methane, it appeared that no appreciable cross-linking had occurred in the process of grafting. © 1996 John Wiley & Sons, Inc.     

Zwitterionic hydrogels crosslinked with novel zwitterionic crosslinkers: Synthesis and characterization

Two novel zwitterionic sulfobetaine dimethacrylate crosslinkersN,N-bis(methacryloxyethyl)-N-methyl-N-(3-sulfopropyl)ammonium (CL1) and N,N-bis(methacryloxyethyl)-N-methyl-N-(4-sulfobutyl)ammonium (CL2) betaines were synthesized and used for preparation of zwitterionic hydrogels formed from N-(methacryloxyethyl)-N,N-dimethyl-N-(3-sulfopropyl)ammonium betaine (SBDMA) via redox-initiated free-radical polymerization. The commercially available crosslinkers N,N′-methylene bisacrylamide (BIS) and ethylene glycol dimethacrylate (EDMA) were also used. Equilibrium water content, sorption degree, diffusion coefficient of water, state of water, degree of crosslinking and mechanical properties were determined for hydrogels crosslinked using different crosslinking conditions. A minor difference in the spacer length between the charged moieties in CL1 and CL2 crosslinkers, respectively, was shown to influence the hydrogel properties. The CL1 and CL2 crosslinkers with chemical structure similar to SBDMA resulted in hydrogels with higher stiffness, mechanical strength and crosslink density compared to hydrogels crosslinked by BIS and EDMA. This difference was assigned to suppression of the compositional drift during the hydrogel formation when crosslinkers with chemical structure similar to monomer were used. PolySBDMA hydrogels exhibited a low adhesion of RAT-2 fibroblasts-like cells.     

From high molecular weight precursor polyrotaxanes to supramolecular sliding networks. The ‘sliding gels’

This paper presents the synthesis and characterization of an original class of supramolecular networks, the ‘sliding’ gels. In this new class of network materials the crosslink points are not fixed but sliding. The molecular structure is based on intermolecularly crosslinked α-cyclodextrins/poly(ethylene-glycol) precursor polyrotaxanes. A synthetic method was developed to obtain various high molecular weight precursor polyrotaxanes with various amounts of α-cyclodextrins (α-CD) per template chain (the so-called degree of complexation, N). The crosslinking reaction of the precursor polyrotaxanes was carried out with the divinyl-sulfone allowing an efficient and good control of the crosslinking density. This control permitted to obtain various network materials with unusual physical/mechanical properties depending on the crosslinker amount and on N. The unusual properties originate from the sliding character of the crosslink points, in these new network materials, which induces a variable and eventually controllable mean mass distribution of the entanglement length. The mechanical spectroscopy and rheological experiments showed two viscoelastic regimes evidencing the molecular mechanism of the change of the mean mass distribution between the crosslink points due to the sliding of α-CD rings on the template PEG chain.     

Tailoring thermoresponsive microbeads in supercritical carbon dioxide for biomedical applications

The preparation of smart polymeric particles in supercritical carbon dioxide (scCO₂) presents many advantages for biomedical applications over conventional processes due to the easy elimination of trace contaminants rendering highly pure particles. Herein we report the successful optimization of poly(N-isopropylacrylamide) (PNIPAAm) synthesis strategy to obtain cell-sized hydrogel microbeads with defined and systematically varied mechanical properties. The effect of using different hydrophilic cross-linkers such as N,N-methylenebisacrylamide (MBAm), di(ethylene) glycol dimethacrylate (DEGDMA) and glycerol dimethacrylate (GDMA), on beads morphological, physico-chemical and mechanical properties was investigated. In agreement with a larger water uptake ability beads cross-linked with DEGDMA are more compliant than those containing MBAm or GDMA, having lower stiffness as accessed through oscillatory measurements on a rotational rheometer. Cytotoxicity assays showed that the obtained cross-linked PNIPAAm microbeads do not present any toxic effect on fibroblast cell cultures. Microbeads biocompatibility and adequate mechanical compliance enable their potential application on biomedical settings.     

Thermally crosslinkable poly(styrene sulfonic acid-co-maleic acid) (PSSA-MA)/polyvinyl alcohol (PVA) ion-exchange fibers

The aim of this study was to prepare poly(styrene sulfonic acid-co-maleic acid) (PSSA-MA)/polyvinyl alcohol (PVA) ion-exchange fibers using the electrospinning technique and a post-thermal treatment. First, intermediate PSSA-MA/PVA fibers were prepared from solutions of PSSA-MA/PVA combined at ratios of 0.2/1 to 1/1; the fibers were subsequently crosslinked at 80–150 °C for 0.25–7 h. The effect of the crosslinking time, the temperature and the PSSA-MA/PVA ratio on various properties of the obtained ion-exchange fibers was investigated. When the PSSA-MA/PVA ratios were greater than 0.4/1, bead formation was observed. Thus, only smooth fibers without beads prepared from PSSA-MA/PVA mixed in ratios up to 0.4/1 were subjected to the thermal crosslinking treatment. When the crosslinking time and temperature were increased, the degree of crosslinking increased, which caused a decrease in the water solubilization and water uptake and an increase in the Young’s modulus. These parameters also appeared to significantly affect the ion-exchange capacity value. The temperature and time for successful crosslinking were 120–140 °C and 1–7 h, respectively.     

Stabilization of higher-order structure of poly(phenyleneethynylene)s by metathesis polymerization at the side chains

Novel poly(m-phenyleneethynlene-p-phenyleneethynylene)s bearing polymerizable diene or norbornene groups were synthesized by the Sonogashira–Hagihara coupling polymerization of the corresponding d-hydroxyphenylglycine-derived diiodo monomers with p-diethynylbenzene. These polymers exhibited strong Cotton effects derived from a predominantly one-handed helical conformation in CHCl₃ and tetrahydrofuran, but exhibited weak or no Cotton effects in N,N-dimethylformamide. The metathesis polymerization of the diene and norbornene moieties was performed at the side chains of the polymers under diluted conditions in the presence of a chain-transfer agent, if necessary. The reaction took place intramolecularly, which was confirmed by size exclusion chromatography (SEC) measurements. The polymers exhibited stronger Cotton effects even in polar media after the intramolecular crosslinking, which indicated stabilization of the predominantly one-handed helical structures.     

Structure and properties of porous poly(vinyl alcohol) hydrogel beads prepared through a physical–chemical crosslinking method

Porous poly(vinyl alcohol) (PVA) hydrogel beads (PC beads) are potential microorganism carriers applied in wastewater treatment industries. However, improving the mechanical strength and stability of traditional PVA hydrogel beads in water is still a challenge. In this research, a new kind of PC bead was successfully prepared by a combination of physical and chemical crosslinking methods. The structures and properties of the PC beads and conventional PVA beads obtained by individual chemical (boric acid) or physical (cyclic freezing and thawing) processes were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and tensile and hydraulic stability testing. Compared with the conventional products, the PC beads displayed a more homogeneous and porous structure, bigger surface area, higher hydraulic stability, and better mechanical properties and showed better applicability for the water treatment field. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46402.     

Solid phase peptide synthesis on an acrylate copolymer attached to porous silica beads

Porous silica beads have been internally coated with a new copolymer prepared from N-[2-(4-acetoxyphenyl)ethyl]acrylamide and N-[3-(triethoxysilyl)propyl]acrylamide. The derivatized silica beads have been used as a solid phase support for the synthesis of the opoid heptapeptide H-Try-Gly-Gly-Gly-Lys-Met-Gly-OH.     

Preparation of Dicarboxylic Acid Containing Sulfonamide Based Resin and Removal of Basic Dyes

Polymer and dye interaction leading to polymer-dye complex formation exhibits many interesting and important practical features. For this purpose, dicarboxylic acid containing resin was prepared in two steps starting from poly (styrene-divinyl benzene) (PS-DVB) (10% crosslinking) based beads with a particle size of 400-590 µm, according to the synthetic protocol; chlorosulfonation, sulfamidation with iminodiacetic acid. Dye extraction experiments were carried out by contacting wetted resin samples with aqueous dye solutions at room temperature. Capacities were determined by colorimetric analysis of the residual dye content. Dye sorption capacity of the resin was found to be (0.67-0.63 g g^?1 resin). This material is also able to remove the cationic dyes completely even from highly diluted aqueous dye solutions.     

Preparation of interpenetrating polymer network gel beads for dye absorption

Preparation of interpenetrating polymer network (IPN) gel beads for dye absorption was carried out by using simultaneous crosslinking method. First, sodium alginate (SA), 3‐(methacrylamido) propyl trimethyl ammonium chloride (MAPTAC), and/or acrylamide (AM), K₂S₂O₈, and N,N′‐methylenebisacrylamide (MBAM) were mixed in aqueous solution. The beads were prepared using K₂S₂O₈ and MBAM as the initiator and crosslinking agent, respectively. Then, the solution was dropped into CaCl₂ solution mixed with N,N,N′,N′‐tetramethylethylenediamine (TMEDA). The former was used as the crosslinking agent of alginate and the latter was used as the accelerator for the polymerization of monomer in the alginate solution. The gel bead composed of only alginate was also prepared to compare the properties with IPN gel bead. The components in IPN gel bead were examined by FTIR analysis. The factors effecting the particle size of alginate and IPN gel beads were investigated. In alginate gel bead, the concentration of solution affected the particle size, whereas type of monomer affected the particle size of IPN gel bead. The IPN gel bead had smooth surface (from SEM results), different from the alginate bead. Alginate content caused the swelling behavior of dried IPN beads. Cationic dye was absorbed by crosslinked alginate gel bead. The absorption of reactive dye by IPN gel bead was a result of its cationic charge. The absorption density of IPN gel beads was the reciprocal of the absorbent dosage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1585–1591, 2006     

Effects of Acylation and Crosslinking on the Material Properties and Cadmium Ion Adsorption Capacity of Porous Chitosan Beads

Abstract

Chitosan is a novel glucosamine biopolymer derived from the shells of marine organisms. This biopolymer is very attractive for heavy metal ion separations from wastewater because it is selective for toxic transition metal ions over less toxic alkali or alkane earth metal ions. Highly porous, 3-mm chitosan beads were prepared by an aqueous phase-inversion technique for casting gel beads followed by freeze drying. In the attempt to simultaneously improve material properties and adsorption capacity, chitosan was chemically modified by 1) homogeneous acylation of amine groups with nonanoyl chloride before bead casting, and 2) heterogeneous crosslinking of linear chitosan chains with the bifunctional reagent glutaric dialdehyde (GA) after bead casting but before freeze drying. The random addition of C₈ hydrocarbon side chains to about 7% of the amine groups on uncrosslinked chitosan beads via N-acylation improved the saturation adsorption capacity from 169 to 216 mg Cd²⁺/g-bead at saturation (pH 6.5, 25°C) but only slightly reduced solubility in acid solution. Crosslinking of the N-acylated chitosan beads with 0.125 to 2.5 wt% GA in the crosslinking bath increased the internal surface area from 40 to 224 m²/g and rendered the beads insoluble in 1 M acetic acid (pH 2.36). However, crosslinking of the N-acylated chitosan beads reduced the saturation adsorption capacity to 136 mg Cd²⁺/g-bead at 0.75 wt% GA and 86 mg Cd²⁺/g-bead at 2.5 wt% GA. Crosslinking also significantly reduced the compression strength. There was no clear relationship between internal surface area and adsorption capacity, suggesting that the adsorbed cadmium was not uniformly loaded into the bead.     

The effect of synthesis methods on the mechanical properties of self‐crosslinkable poly(n‐butyl methacrylate‐co‐N‐methylolacrylamide) films

The effects of particle size and parent polymer characteristics on the mechanical properties, gel fraction, and swelling index of self‐crosslinkable poly(n‐butyl methacrylate‐co‐N‐methylolacrylamide) films made by two‐stage emulsion or microemulsion polymerization in the presence of variable amounts of the chain transfer agent, n‐butyl mercaptan, are reported here. In films prepared with latexes made by microemulsion polymerization, the crosslinking degree increased greatly on curing; by contrast, in those made by emulsion polymerization, the crosslinking degree practically did not increase after curing. Stress–strain tests of uncured and cured films indicate that microemulsion‐made films are tougher than the emulsion‐made films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photopolymerised thermo-responsive poly(N,N-diethylacrylamide)-based copolymer hydrogels for potential drug delivery applications

Novel thermo-sensitive N,N-diethylacrylamide (DEAAm) based copolymer hydrogels were prepared via UV-induced free radical bulk polymerisation. UV polymerisation was employed to avoid the use of potentially toxic solvents; solution polymerisation has been the most common means for the preparation of PDEAAm-based hydrogels in the literature to date. The resultant hydrogels were analysed using nuclear magnetic resonance, Fourier transform infrared spectroscopy and modulated differential scanning calorimetry. Parameters such as the crosslinking degree and the nature of the incorporated hydrophilic component, N-vinyl-2-pyrrolidone (NVP) or N,N-dimethylacrylamide (DMAAm) were found to impact hydrogel structure, mechanical properties and swelling kinetics. Pulsatile swelling studies indicated that the hydrogels had thermo-reversible properties which were greatly affected by test temperature, nature of hydrophilic monomer used and crosslinker content. Aminophylline was selected as a model solute for drug loading and release studies by thermal deswelling in HCl buffer (pH 1.4) and phosphate buffer media (pH 6.8). The observed lag time prior to significant drug release from the more crosslinked P(DEAAm-NVP) hydrogels could make them suitable for delayed specific release in the intestine and potential alternatives to layers or membranes in time-specific and site-specific swelling-controlled drug delivery systems.     

Semi‐interpenetrating networks based on poly(N‐isopropyl acrylamide) and poly(N‐vinylpyrrolidone)

Three series of novel semi‐interpenetrating polymer networks, based on crosslinked poly(N‐isopropylacrylamide), PNIPA, and different amounts of the linear poly(N‐vinylpyrrolidone), PVP, were synthesized to improve the mechanical properties and thermal response of PNIPA gels. The effect of the incorporation of the linear PVP into the temperature responsive networks on the temperature‐induced transition, swelling/deswelling behavior, and mechanical properties was studied. Polymer networks with four different crosslinking densities were prepared with varying molar ratios (25/1 to 100/1) of the monomer (N‐isopropylacrylamide) to the crosslinker (N,N′‐methylenebisacrylamide). The hydrogels were characterized by determination of the equilibrium degree of swelling, the dynamic shear modulus and the effective crosslinking density, as well as tensile strength and elongation at break. Furthermore, the deswelling kinetics of the hydrogels was studied by measuring their water retention capacity. The inclusion of the linear hydrophilic PVP in the PNIPA networks increased the equilibrium degree of swelling. The tensile strength of the semi‐interpenetrating networks (SIPNs) reinforced with linear PVP was higher than that of the PNIPA networks. The elongation at break of these SIPNs varied between 22% and 55%, which are 22 – 41% larger than those for pure PNIPA networks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Super‐macroporous dextran cryogels via UV‐induced crosslinking: synthesis and characterization

Cryogenic treatment and UV irradiation were exploited for the preparation of super‐macroporous cryogels from non‐modified high‐molar‐mass dextran. The photo‐crosslinking process was initiated by (4‐benzoylbenzyl)trimethylammonium chloride and N,N′‐methylenebisacrylamide (BAAm) was used as a crosslinking agent. Gel fraction yield and degree of swelling of the dextran cryogels were determined gravimetrically. Cryogel morphology and mechanical properties were studied using environmental scanning electron microscopy and dynamic rheological measurements, respectively. The effects of dextran concentration in the initial polymer solution, polymer molar mass and BAAm content on the crosslinking efficacy, physico‐mechanical properties and morphology of the cryogels were evaluated. The dextran cryogels were assessed as carriers of the model water‐soluble drug metoprolol. © 2017 Society of Chemical Industry     

液体聚硫橡胶对聚硫密封剂性能的影响

以G系列液体聚硫橡胶为生胶、MnO2为密封剂的硫化剂,制备相应的聚硫密封剂。考察了生胶的不同相对分子质量(Mr)和交联度对相应密封剂性能的影响。结果表明:不同Mr或交联度的生胶均赋予相应密封剂良好的力学性能,特别是由低Mr的G44制成的密封剂具有相对更好的力学性能;密封剂的耐高温性能与生胶的Mr关系不大,主要受交联度影响较大;生胶的Mr越大或交联度越高,密封剂的耐水性越好,但Mr或交联度对密封剂的耐油性能(增重率<3%)和粘接性能影响较小。