Novel Interpenetrating Networks (IPNs) Hydrogels Prepared In Situ by Liquid-Phase Photopolymerization

Novel interpenetrating networks (IPNs) hydrogels responsive to temperature were prepared in situ by liquid-phase photopolymerization. The first network of the IPNs (poly isopropyl acrylamide) were formed with a special kind of hectorite (Laponite XLS) modified by tetrasodium pyrophosphate as cross-linker and 2-oxogultaric acid as photoinitiator. The samples were subsequently immersed in an acrylamide (AAm) aqueous solution for at least one day for preparing IPNs hydrogels, in which acrylamide aqueous solution containing N,N′-Dimetyl acrylamide (MBAA) as cross-linker and 2-oxogultaric acid as photoinitiator. Then the second networks were in situ formed by introducing ultraviolet light irradiated PNIPAAm gels. The swelling/deswelling behaviors of IPNs hydrogels were measured. Compared with the corresponding nanocomposite PNIPAAm hydroges(NC hydrogels), chemically cross-linked PNIPAAm and PAAm IPNs hydrogels, the results indicate that the new IPN hydrogel has a faster deswelling rate above its LCST (≈32 °C). The effect was explained as being an additional contribution of the PAAm chains in IPN hydrogels, which may act as a water-releasing channel when the hydrophobic aggregation of PNIPA takes place.     

Coating of Tetraethylorthosilicate (TEOS)/Vinyltriethoxysilane (VTES) Hybrid Solution on Polymer Films

Tetraethylorthosilicate (TEOS)/vinyltriethoxysilane (VTES) hybrid materials were prepared and the hydrolysis and condensation reactions during processing were investigated by means of 29Si NMR solution spectroscopy. The variation of drying characteristics of the coating films was examined with respect to the tetraethylorthosilicate (TEOS)/vinyltriethoxysilane (VTES) ratio, as well as drying temperature, by FT-IR spectroscopy. It is shown that the TO mode of Si–O–Si stretching absorption was enhanced with increasing tetraethylorthosilicate (TEOS) content and drying temperature. Also, the wettability of the coating films on polymer films was independent of the solution composition but enhanced by the precoating of poly(4-hydroxystrene) (PHS) as a wetting agent. The adhesion between the coating and the films was also enhanced when the vinyltriethoxysilane (VTES) content in the coating solution was increased.     

Conducting Polyaniline Confined in Semi‐Interpenetrating Networks

Conducting semi‐interpenetrating network composites with low conductivity percolation threshold were synthesized from waterborne conducting polyaniline (cPAn) and melamine‐urea resin. A perfect network of cPAn in the composite was observed by means of TEM (see Figure). The conductivity stability of cPAn in water was improved by confining the chain mobility of cPAn via in‐situ crosslinking of melamine‐urea resin. Cyclic voltammetry of the composites reveals electrochemical activities and reversibilities similarly to those of pure cPAn.     

Interpenetrating Polymer Networks with Spatially Graded Morphology Controllable by UV-Radiation Curing

Interpenetrating Polymer Networks (IPNs) composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were synthesized from a precursor mixture by using dissimilar photo-cross-link reactions. When the reation yields exceeded a certain threshold, the mixture was quenched from one-phase region into two-phase region, leading to phase separation. Upon irradiation with strong UV-light, an intensity gradient was formed along the propagating direction of the exciting light, generating a gradient of quench depth via the spatial inhomogeneity of the cross-link reactions. As a consequence, a gradient of the characteristic length scales was continuously generated from the top to the bottom of the mixture. The resulting three-dimensional (3-D) morphology was in-situ observed at different depths of the mixture by using a laser-scanning confocal microscope (LSCM). From this 3-D observation, it was found that phase separation was accelerated at the bottom of the mixture and proceeded in an autocatalytic fashion. The mechanism for the formation of the graded morphology was discussed in conjunction with the kinetics of the autocatalytic phase separation.     

Interpenetrating polymer networks of poly(carbonate-urethane) and polyvinyl pyridine

Simultaneous interpenetrating polymer networks (IPN's), pseudo IPN's, and liner blends of aliphatic poly(carbonate-urethane) (PCU) and polyvinyl pyridine (PVP) have been prepared and characterized by DSC, DMA, and TEM. The full IPN's of PCU and PVP had a single phase morphology only above 50 wt % PCU, as determined by both DSC and DMA and confirmed by transmission electron microscopy (TEM). However, in both pseudo IPN's of PCU and PVP and in their linear blends there exist multiple glass transitions and melting points seen by DSC and DMA indicating phase incompatibility. The full IPN's exhibited superior ultimate mechanical properties and solvent resistance as compared to the pseudo IPN's, liner blends, and the pure crosslinked PCU and PVP networks.     

聚氨酯互穿聚合物网络阻尼性能研究进展

介绍了聚氨酯互穿聚合物网络（ＰＵ ＩＰＮ）作为阻尼材料的研究进展,分别讨论了聚氨酯（ＰＵ）／环氧树脂（ＥＰ）ＩＰＮ和ＰＵ／乙烯基聚合物ＩＰＮ的阻尼性,以及影响阻尼性能的因素,并比较了不同类型的ＰＵ ＩＰＮ的优缺点及新的可能的探讨方向。     

Scaffolds of Hyaluronic Acid–Poly(Ethyl Acrylate) Interpenetrating Networks: Characterization and In Vitro Studies

Hyaluronic acid (HA) provides many advantages to regenerative implants through its bioactive properties, but it also has many limitations as a biomaterial if it is not chemically modified. In order to overcome some of these limitations, HA has been combined with poly(ethyl acrylate) in the form of interpenetrating polymeric networks (IPNs), in which the HA network is crosslinked with divinyl sulfone. Scaffolds of this IPN have been produced through a template‐leaching methodology, and their properties have been compared with those of single‐network scaffolds made of either PEA or crosslinked HA. A fibroblast cell line has been used to assess the in vitro performance of the scaffolds, revealing good cell response and a differentiated behavior on the IPN surface when compared to the individual polymers. Altogether, the results confirm that this type of material offers an interesting microenvironment for cells, which can be further improved toward its potential use in medical implants.

     

聚氨酯／聚（苯乙烯—甲基丙烯酸甲酯—甲基丙烯酸互穿聚合物网络的研究

研究了聚氨酯／聚互穿合笺网络，动态力学性能及透射电镜结果均表明该体系相分离较严重。ＩＮＰ具有两个玻璃化转变温度，它们有不同程度的内移，形成一定程度分子水平的混合。而ＩＰＮ（５０／５０）其分子混合水平较大，互穿缠结程度较高。     

聚氨酯／聚（苯乙烯－甲基丙烯酸甲酯－甲基丙烯酸）互穿聚合物网络的研究

研究了（蓖麻油－聚乙二醇）聚氨酯／聚（苯乙烯－甲基丙烯酸甲酯－甲基丙烯酸）（ＰＵ／Ｐ（Ｓｔ－ＭＭＡ－ＭＡＡ））互穿聚合物网络（ＩＰＮ）．动态力学性能及透射电镜结果均表明该体系相分离较严重；ＩＰＮ具有两个玻璃化转变温度，它们有不同程度的内移，形成一定程度分子水平的混合，而ＩＰＮ（５０／５０）其分子混合水平较大，互穿缠结程度较高。形成ＩＰＮ后，其力学性能得以改善。透射电镜结果表明，聚氨酯网的交联密度直接影响ＩＰＮ的相区尺寸。形成ＩＰＮ后热稳定性提高，易于降解断链的Ｓｔ－ＭＭＡ－ＭＡＡ单体起到了自由基消除剂的作用。     

In situ Synthesis of Magnetic Iron Oxide Nanoparticles in Thermally Responsive Alginate‐Poly(N‐isopropylacrylamide) Semi‐Interpenetrating Polymer Networks

A novel semi‐interpenetrating polymer network based on alginate and poly(N‐isopropylacrylamide) (PNiPAAm) has been synthesized that shows response to temperature and magnetic fields. Highly homogeneous porous hydrogels are obtained by copolymerizing N‐isopropylacrylamide and bis‐acrylamide in the presence of an aqueous alginate solution. The synthesis of magnetic iron oxides by in‐situ oxidation of iron cations coordinated to the alginate network results in a hydrogel with an enhanced deswelling rate with respect to pure PNiPAAm.

     

Transparent inorganic/organic copolymers by the sol-gel process: Thermal behavior of copolymers of tetraethyl orthosilicate (TEOS), vinyl triethoxysilane (VTES) and (meth)acrylate monomers

Three types of inorganic/organic copolymers have been prepared in a one-step sol-gel process, and their thermal stabilities have been studied. The one-step sol gel process was carried out in mixtures of three monomeric components: HEMA (hydroxyethyl methacrylate)-VTES (vinyl triethoxysilane)-TEOS (tetraethyl orthsilicate), HDDA (hexanediol diacrylate)-VTES-TEOS and GPTA (glycerol propoxy triacrylate)-VTES-TEOS. Copolymers with HEMA, which is able to form a linear organic polymer, were the least thermally stable materials. They lost the highest proportion of weight during heat treatment to 600°C and exhibited the lowest decomposition temperatures. Copolymers with HDDA and GPTA, which are able to form crosslinked organic polymers, had higher decomposition temperatures, and their weight loss during heat treatment to 600°C was small. The skeletal densities of all copolymers increased slightly during heat treatment.     

Interpenetrating polymer networks of poly(dimethyl siloxane–urethane) and poly(methyl methacrylate)

Simultaneous IPNs of poly(dimethyl siloxane-urethane) (PDMSU)/poly(methyl methacrylate) (PMMA) and related isomers have been prepared by using new oligomers of bis(β-hydroxyethoxymethyl)poly(dimethyl siloxane)s (PDMS diols) and new crosslinkers biuret triisocyanate (BTI) and tris(β-hydroxylethoxymethyl dimethylsiloxy) phenylsilane (Si-triol). Their phase morphology have been characterized by DSC and SEM. The SEM phase domain size is decreased by increasing crosslink density of the PDMSU network. A single phase IPN of PDMSU/PMMA can be made at an M_c = 1000 and 80 wt % of PDMSU. All of the pseudo- or semi-IPNs and blends of PDMSU and PMMA were phase separated with phase domain sizes ranging from 0.2 to several micrometers. The full IPNs of PDMSU/PMMA have better thermal resistance compared to the blends of linear PDMSU and linear PMMA. © 1993 John Wiley & Sons, Inc.     

反应注射成型聚氨酯互穿聚合物网络的进展

本文将介绍有关反应注射成型聚氨酯同步互穿聚合物网络（ＲＩＭ ＳＩＮ）方面的研究工作。综合文献报道和我们研究扬实验工作，重点描述了不饱和聚酯树脂或乙烯基酯树脂为刚性相的聚氨酯互穿聚合物网络，讨论了它们的生成反应动力学及其形态结构发展进程，并与样品力学性能相关联。     

Hydrolysis and polycondensation of ethyl silicates. 1. Effect of pH and catalyst on the hydrolysis and polycondensation of tetraethoxysilane (TEOS)

The effect of pH and of catalysts on the course of the hydrolysis and condensation of tetraethoxysilane (TEOS) in water—ethanol solution was studied with the aid of chromatography, potentiometry and gelation tests. Strong acids (HCl, HClO₄, HNO₃, H₂SO₄, p-toluenesulphonic acid), weak acids (Cl₃CCOOH, (COOH)₂, ClCH₂COOH, CH₃COOH, HCOOH) and LiOH were used as catalysts. The rate of hydrolysis depended on the pH of the solution and not on the chemical structure of the catalyst. The hydrolysis was both acid and base catalysed and its rate was at a minimum at pH 7.0.

The rate of condensation of the reaction products of the hydrolysis of TEOS (water—ethanol solutions of ethoxyhydroxysiloxanes) was at a minimum at a pH of about 2.0. The condensation was both acid and base catalysed and was markedly accelerated by both HF and H₃PO₄.     

Interpenetrating Polymer Networks of Uralkyd Resin Based on Hydrogenated Castor Oil and Poly(Butyl Acrylate)

Abstract

Semi‐ and full‐interpenetrating polymer networks (IPNs) of uralkyd (UA) resin based on hydrogenated castor oil and poly(butyl acrylate) (PBA) were prepared by the sequential mode of synthesis. These IPNs were characterized for their resistance to thermal behavior, swelling (%), and mechanical properties. The morphology of the IPNs was studied by scanning electron microscopy (SEM). The effect of the variations of the blend ratios on the above‐mentioned properties was examined. The mechanical properties significantly enhanced by increasing UA component in the blend. Full‐IPNs exhibited higher apparent densities, mechanical properties, and thermal stability than the corresponding semi‐IPNs.     

Interpenetrating polymer networks based on polyurethane and poly(butyl methacrylate): Interrelation between reaction kinetics and microphase structure

The effect of the reaction kinetics on the formation of semi-IPNs based on crosslinked polyurethane and linear poly(butyl methacrylate) of various compositions has been studied. New data are presented concerning the interconnection between the reaction kinetics, gelation and rheokinetics of IPN formation, between kinetics and crosslinking density, microphase structure and degree of microphase separation. It was shown that kinetic factors determine the conditions of microphase separation and formation of microphase structure.     

Transparent inorganic/organic copolymers by the Sol-Gel process: Copolymers of tetraethyl orthosilicate (TEOS), vinyl triethoxysilane (VTES) and (meth)acrylate monomers

Vinyl triethoxysilane (VTES) and (meth)acrylate monomers were mixed to create covalently bonded inorganic/organic copolymers, with and without tetraethyl orthosilicate (TEOS). Vinyl groups underwent free radical polymerization along with copolymerization with (meth)acryl groups of the monomer. For the two-monomer system, (meth)acrylate monomer and VTES, polymerization resulted in mechanically strong copolymers with flexure strengths greater than 40 MPa. Three-component materials obtained by polymerization of (meth)acrylate monomer, VTES and TEOS were homogeneous, highly transparent, with flexure strengths similar to those for silica xerogels, about 20 Mpa.