Increased enzyme activity in immobilised cell composites with a highly hydrophilic polymer matrix

Streptomyces phaeochromogenes cells were immobilised by radiation polymerisation of hydrophilic monomers; highest levels of glucose isomerase activity were found in immobilised cell composites with highly hydrophilic polymer matrices. The enzyme activity in the composites from the copolymerisation of hydroxyethyl acrylate (or methacrylate) and N-vinyl-2-pyrrolidone monomer increased markedly with increase in the content of the N-vinyl-2-pyrrolidone monomer, owing to the higher water absorption by the polymer matrix, and was close to that of the non-immobilised cells. The enzyme activity was affected by monomer concentration, the hydrophilicity, and chemical structure of the polymer matrix. The Michaelis constant of the composites from hydrophilic monomers was close to that of the intact cells.     

Synthesis of smart hydrogels by radiation polymerisation for use as slow drug delivery devices

This article deals with the modification of medicinally important psyllium polysaccharide with acrylamide through radiation crosslinked polymerisation for the design of double potential hydrogels meant for slow release of insulin. Here the double potential is due to the inherent blood sugar lowering ability of psyllium and release of insulin in controlled manner from the drug loaded hydrogels. Synthesis of hydrogels and their characterisation by scanning electron micrography (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and swelling studies have been discussed. The release dynamics of model drug insulin from the hydrogels has been studied for the evaluation of the release mechanism. The release of the drug from the hydrogels occurred through non‐Fickian diffusion mechanism.     

Optimised immobilisation of microbial lipase on hydrous niobium oxide

The aim of this work was to establish appropriate conditions for immobilising Candida rugosa lipase on a low‐cost inorganic matrix, hydrous niobium oxide, using a multivariate statistical approach. A 2³ full factorial design was employed to determine the effects of support activation with glutaraldehyde (concentration 2.5–4.5%, pH 7–10) and lipase loading (200‐700 U g^?1 matrix) on the hydrolytic and synthetic activities of the immobilised derivatives. From the results the following conditions were established: lipase loading of 450 U g^?1 matrix and niobium oxide activation with glutaraldehyde at a concentration of 2.5% and pH 8. Under these conditions, high activity recovery (47.21%) and esterification yield (86.90%) were attained. The results also show that hydrous niobium oxide can be a valid alternative to replace high‐cost, commercially available inorganic matrices such as controlled pore silica. Copyright © 2006 Society of Chemical Industry     

Using controlled radical polymerisation techniques for the synthesis of functional polymers containing amino acid moieties

There is great current interest in bridging the gap between robust synthetic polymers and complex biological polymers to allow for the preparation of novel functional, well‐defined, biocompatible and tailorable materials. In this mini‐review recent reports on the preparation of functional amino acid polymers using controlled radical polymerisation techniques are discussed. The future potential applications of these materials as well as the proposed further directions in the field are also highlighted. Copyright © 2010 Society of Chemical Industry     

Stochastic model for living radical polymerisation of styrene initiated by epoxide radical ring opening

A stochastic model was developed to simulate the polymerisation kinetics and the detailed microstructure of the resulting polymers made by the living radical polymerisation of styrene initiated by epoxide radical ring opening. The model was used to predict monomer conversion, average molecular weight, polydispersity index, and molecular weight distribution as a function of polymerisation time. Simulations were used to explore the effects of rate constant values on chain microstructures and polymer properties and validated with experimental data published in the literature. It was found that some parameters, such as the exchange rate constant, have no significant effect on the polymerisation kinetics, whereas major effects were observed when other rate constants, such as the reduction rate constant, were changed.     

辐射接枝改性聚合物的研究进展

本文介绍了辐射接枝技术改性聚合物的研究与应用情况，并讨论了辐射接枝过程中的主要影响因素。     

高分子吸水剂的辐射聚合及其性能研究

利用^60Coγ射线引发辐射聚合,合成了聚丙烯酸钠、聚丙烯酸-丙烯腈、聚丙烯酸-醋酸乙烯、聚乙烯醇接枝丙烯酸等几种高分子吸水剂,考察了辐射剂量对单体聚合和吸水倍数的影响,并对所合成高分子吸水剂的吸水特性进行了研究。     

Immobilization of microbial cells on cellulose–polymer surfaces by radiation polymerization

Streptomyces phaeochromogenes cells were immobilized on cellulose–polymer surfaces by radiation polymerization using hydrophilic monomers and paper. The enzyme activity of immobilized cell sheets was higher than that of immobilized cell composites obtained by the usual radiation polymerization technique. The enzyme activity of the sheets was affected by monomer concentration, the thickness of paper, and the degree of polymerization of paper. The copolymerization of hydroxyethyl methacrylate and methoxytetraethyleneglycol methacrylate in the sheets led to a further increase of the enzyme activity due to the increase of the hydrophilicity of the polymer matrix. The Michaelis constant of the sheets from low monomer concentration was close to that of intact cells.     

Chelating polymer granules prepared by radiation‐induced homopolymerization. I—Kinetic study of radiation polymerization process

Chelating polymer granules containing amidoxime chelating groups were synthesized by radiation‐induced homopolymerization of acrylonitrile monomer. The chemical reactive intermediate polyacrylonitrile was treated with hydroxylamine solution to convert the chemical active cyano groups into the amidoxime groups. Kinetic study of the effects of monomer concentration, radiation dose, dose rate, and temperature on the polymerization process was investigated. It was found that at low monomer concentration, the rate of polymerization is roughly independent on the initial monomer concentration, while at high monomer concentration, 35–65%, a marked acceleration on the rate was observed. The order of the dependence of the initial rate of polymerization on the dose rate is 0.77, which deviates from the classical square‐root law due to the precipitation of the formed polymer. The conversion percent and molecular weight of the produced polymer are inversely proportional to dose rate at constant radiation dose. The activation energy was found to be 2.7 kcal/mol, and the rate constant of initiation is independent of temperature. The effect of type of solvent on the polymerization was studied. DMF solvent of the closest solubility parameter to the solubility parameter of polyacrylonitrile is the best solvent for the polymerization process. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1405–1412, 2000     

Polyaniline/porous carbon electrodes by chemical polymerisation: Effect of carbon surface chemistry

Polyaniline/porous carbon composite electrodes were prepared by chemical polymerisation and characterized in terms of porosity and performance as electrochemical capacitors.To obtain the composite electrodes two methods were used. The first method consisted of mixing, directly, the activated carbon with chemically polymerised polyaniline. The second one consisted of mixing the activated carbon with aniline and subsequent chemical polymerisation. Additionally, the second process was carried out with the porous carbon previously thermally treated in N₂ up to 900 °C in order to remove surface oxygen groups.Changes in porosity with the polyaniline addition were analysed. It has been proved that the method used strongly affects the porous structure. Dealing with the electrochemical performance, polyaniline and carbon mechanically mixed seem to work independently, being the composite behaviour a combination of the corresponding performance of both materials separately. The composites prepared by the second method (polymerisation over carbon) reveal the key role of surface chemistry in polyaniline coating. Aniline reacts with the oxygen complexes and their positive effect in capacitance is not observed.The second method (polymerisation over carbon) using a thermally treated carbon seems to be the best one since a more porous (or thinner) polyaniline film is produced.     

不同聚合物基体对复合材料性能的影响

研究了以不同类型聚合物为基体的高分子夏合材料的导电性和力学强度的变化规律，并从聚合物的结晶性，对填料的粘结性及其表面张力等方面进行了分析。若基体的结晶性和极性较强，则在导电性提高的同时，冲击强度下降；若基体本身比较柔软且对填料有足够的亲和力，则在一定的填料含量范围内，导电性和冲击强度可同时提高。     

Influence of moisture on the photochemically induced polymerisation of epoxy groups in different chemical environment

The influence of atmospheric humidity on the photochemically induced cationic polymerisation of epoxy groups in different chemical environments is shown. With increasing humidity, the polymerisation rate of glycidylethers decreases, whereas for epoxides with endocyclic epoxy groups the rate of polymerisation increases and the rate for epoxides with exocyclic epoxy groups is nearly not influenced. The reasons for the different behaviour are energetic differences for the reactions between the positively charged chain ends with water and the following proton transfer. Furthermore the reaction rate is influenced by the different stereochemistry of the attack of the next monomer.     

Redox polymerisation—kinetics of polymerisation of acrylamide initiated by the Mn3+-citric acid redox system

The kinetics and mechanism of polymerisation of acrylamide initiated by manganese(III) acetate-citric acid (CA) redox system in aqueous acetic acid and sulphuric acid medium were studied over the temperature range 30-50° C. The overall rates of polymerisation (R_p), disappearance of manganic ion (—R_m), and degree of polymerisation (X?_n) were measured with variation in [monomer], [Mn³⁺], [CA], [H⁺], μ and temperature. The polymerisation is initiated by the organic free radical arising from the Mn³⁺-CA reaction and the termination is by metal ions. The various rate parameters were evaluated and discussed.     

Studies on the kinetics of photo-initiated radical polymerisation of modified epoxy resin

The diglycidyl ether of bisphenol-A (DGEBPA) was modified by acrylic acid. The reaction between the active epoxy groups of DGEBPA and the carboxylic group of acrylic acid was catalysed by triphenyl phosphine to prepare di(vinyl-2-hydroxypropanoate) ether of bisphenol-A (DEBA). The DEBA so formed was co-polymerised with 2-ethylhexylacrylate using benzophenone as the photo-initiator to yield a flexible polymer. The kinetics of the photo-initiated radical polymerisation was studied by a new technique called differential photo-calorimetery and the results thus obtained were analysed to determine the Arrhenius activation energy and pre-exponential factor.     

Effects of diacrylate monomers on the bond strength of polymer concrete to wet substrates

The bond strengths of polymer concretes containing up to 15% (based on polymer resin) of diacrylate (DA) monomers were examined and compared with those without DA. A change occurring with the addition of DA monomers was an increase in the bond strength of polymer concrete to wet substrates. Zinc diacrylate (ZDA) and calcium diacrylate (CDA) were each used as an additive to monomers and resins [methyl methacrylate (MMA), polyester, and two kinds of epoxies]. The variables were amount of the DA monomers and surface conditions (wet or dry and smooth or rough). Bond strengths were measured by tension bond. ZDA was found to improve the bond strength of MMA and polyester, whereas CDA improved the bond strength of epoxies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 991–1000, 2003     

辐射加工技术在医用高分子材料中的应用研究进展

介绍了辐射加工技术的特点,概述了它在医用高分子材料方面的应用研究情况,并综述了其主要研究进展。     

Drop stabilisation by inorganic solids in suspension polymerisation: Effect of inorganic particle size using a wax model

Inorganic solids can be used for drop stabilisation in suspension polymerisation and, in some cases, the particle size can affect the drop stability significantly. Three theoretical models, each based on different theories for this drop stabilisation by inorganic solids, have been formulated. Experiments have been carried out using a wax model. These experiments were similar to those described previously [Brooks, B. W., Bygate. F. & Lane, A. C, Brit. Polym. J., 20 (1988) 19-24; Brooks, B. W., Trans. I. Chem. E., 57 (1979) 210-12]. Particulate calcium phosphate, in different sizes, was used as the stabiliser. The theoretical models have been compared with the experimental results and it was found that two of the models bore some resemblance to the experimental results.     

Influences of metallic polymeric materials on the properties of fresh polyester and acrylic polymer concrete

To investigate the influences of three metallic polymeric materials in polyester and acrylic fresh polymer concretes (PCs), PC‐incorporated different levels of these materials have been investigated for their properties of fresh PC. The mix design was made and optimized for workability, strength, and economy, depending on the resin viscosity, the intended use, and the additional quantities of these polymeric materials. The properties investigated include workability, working time, and curing time of fresh PC. It is concluded that these polymeric materials offer the possibility of improving properties of polyester and acrylic fresh polymer concretes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Determination of the methyl methacrylate monomer in its polymer latex by headspace gas chromatography

This article reports a headspace gas chromatography (GC) method for the determination of the residual monomer in a methyl methacrylate polymer latex or emulsion. Because of the multiphase nature of a polymer latex, the level of the residual monomer cannot be quantified by headspace GC on the basis of its vapor–liquid equilibrium (VLE) without significant thermodynamic assumptions. With a significant dilution of a polymer latex sample followed by vapor–liquid equilibration at an elevated temperature, the monomer droplets are completely dissolved in the aqueous phase, and monomer absorption in the polymer particles can be minimized. Thus, VLE is established in the diluted latex, and a linear relationship between the monomer concentration in the vapor and aqueous phases can be obtained. This technique eliminates sample pretreatment procedures such as solvent extraction in the conventional GC method, and it avoids the risk of polymer deposition on the GC column caused by a direct injection of a monomer‐containing solvent. It also eliminates the possibility of solvent interference in the conventional GC monomer analysis. This method is simple, accurate, and automated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 392–397, 2006     

辐射引发分散聚合反应制备聚合物微球研究进展

介绍了辐射作用原理、辐射引发分散聚合反应技术和机理、及其最新研究进展：重点阐述了超声、紫外光、γ射线、微波辐射在分散聚合中的应用。