尺寸排除色谱扩展因子的分子量依赖性与填料的孔洞表面结构

用聚苯乙烯标样作为探针,对多种SEC柱的分离和扩展效应作同时的校准,扩展因子随探针分子量的增加而增大,增大的幅度与SEC填料的孔洞表面结构有关。大孔径多孔硅球的比表面积较低,孔洞表面比较平滑,溶质分子在孔洞中运动时阻碍粳少,高分子量聚苯乙烯(M?10~6)的扩展因子只比低分子量(M?10~3)的大2—3倍。交联聚苯乙烯型凝胶的比表面积较大,表面比较粗糙,高分子量探针的扩展因子要比低分子量的高出几十倍,显示溶质分子在孔洞中运动所受阻碍较大。后一现象可用有机交联凝胶永久性孔洞的骨架表面具有自由链端得到说明。     

交联聚苯乙烯型多孔吸附剂的中孔性质研究

采用77K温度下的氮气吸附方法,测定了经悬浮聚合制备的不同交联度的交联聚苯乙烯多孔吸附剂的吸附/脱附等温线.根据BET吸附模型计算了比表面,由吸附量计算了总的孔体积,由孔体积和比表面计算出平均孔径,并依据脱附等温线采用BJH方法计算孔径分布.结果表明,交联度对交联聚苯乙烯多孔吸附剂的孔结构均具有显著影响.随着交联聚苯乙烯多孔吸附剂的交联度升高,其孔径变小,比表面增大,而且低交联度吸附剂的中孔接近圆柱形,高交联吸附剂的中孔形状接近“墨水瓶”形.显然,交联度对孔性质的影响与孔结构在交联聚苯乙烯多孔吸附剂制备和后处理过程中的稳定性密切相关.交联度低时,初期形成的小孔不能保持稳定,在后续聚合及后处理过程中合并为大孔,结果造成低交联吸附剂大孔径、低比表面的现象.通过对孔径分布的研究,揭示了不同吸附剂在中孔范围内的孔特征,并对其形成机制进行了分析.     

起始共聚物的结构对超高交联聚苯乙烯的结构和抗溶胀破碎性能的影响

本文以凝胶型低交联聚苯乙烯为起始共聚物，合成了各种超高交联聚苯乙烯，研究了起始共聚物的化学交联和物理缠结对合成的超高交联聚苯乙烯的表面和孔道结构的影响。此外，本文还以干态超高交联聚苯乙烯加入液体介质中时的碎球率为指标，考察了起始共聚物的结构对合成的超高交联聚苯乙烯机械性能的影响。     

起始共聚物的结构对超高效联聚苯乙烯的结构和抗溶胀破碎性…

本文以凝胶型低交联聚苯乙烯为起始共聚物，合成了各种超高效联聚苯乙烯，研究了起始共聚物的化学交联和物理缠结对合成的超高交联聚苯乙烯的表面和孔道结构的影响。     

互贯型螯合树脂的研究(Ⅰ)─交联聚苯乙烯－聚丙烯腈互贯树脂的合成

研究了交联聚苯乙烯-聚丙烯腈新型互贯树脂(PS-PAN)的合成,考察了交联度、重量比、孔结构和溶剂对互贯量的影响。结果表明,以凝胶型树脂为第一网时,交联度的影响比较显着,两网交联度相同时互贯量最大;以大孔型树脂做第一网时,孔结构的作用较突出。此外,溶剂对互贯量的影响非常大。     

磺化聚苯乙烯纳米微球-聚丙烯酰胺杂化水凝胶的制备及性能

首先通过乳液聚合法合成了聚苯乙烯(PS)微球,该微球经浓硫酸磺化后得到了磺化聚苯乙烯(SPS)微球;然后将合成的SPS微球作为多功能交联点加入丙稀酰胺(AAm)化学水凝胶网络中制备了SPS-PAAm杂化水凝胶。通过扫描电镜、透射电镜观察了SPS微球及杂化水凝胶的微观结构。研究了SPS微球对SPS-PAAm杂化水凝胶的凝胶分数、溶胀性能和力学性能的影响。结果显示:随着SPS微球用量的增加,SPS-PAAm水凝胶的凝胶分数先增加后降低,平衡溶胀度降低;SPS微球的加入能改善水凝胶的力学性能,随着SPS含量的增加,水凝胶的拉伸强度和能量损耗增加;SPS微球和PAAm分子链间存在物理相互作用。     

一种四臂聚苯乙烯凝胶的激光光散射研究

采用原子转移自由基方法(ATRP)合成窄分布的末端基为巯基的四臂星型聚苯乙烯(4-PS-SH).巯基容易被空气中的氧气氧化生成二硫键,会引起四臂星型聚苯乙烯分子间交联.利用激光光散射研究了四臂聚苯乙烯在亚浓溶液中氧化交联生成大的胶束进而生成宏观化学凝胶的过程.静态激光光散射测量结果表明四臂聚苯乙烯亚浓溶液以及凝胶样品的时间平均散射光强不随测量位置的变化而涨落,说明此凝胶是结构均一的化学凝胶.动态光散射结果表明在四臂聚苯乙烯亚浓溶液氧化生成凝胶的过程中,动态强度-强度时间相关函数的慢运动衰减的贡献最初随着氧化时间的增加逐渐增强,当氧化反应进行到一定程度时慢运动的贡献又逐渐减弱,最终慢运动消失.生成的化学凝胶的相关函数与最初亚浓溶液的相关函数几乎重合.静态和动态激光光散射结果表明生成的四臂聚苯乙烯凝胶是结构均匀的化学凝胶.     

两步后交联法制备氯甲基化聚苯乙烯交联微球

以平均粒径为40μm的非交联氯甲基化聚苯乙烯(CMPS)微球为出发物料,采用水解-轻度交联与重度交联两步骤的后交联方法,制备了氯甲基化聚苯乙烯交联微球.用红外光谱表征了交联前后微球化学结构的变化,使用扫描电镜观察了交联微球的形貌,重,点考察了各种交联条件对微球交联度的影响规律,分析了交联反应机理.结果表明:先将非交联氯甲基化聚苯乙烯微球部分水解并轻度交联,然后使CMPS微球在良溶剂中溶胀,使用Friedel-Crafts催化剂,再度进行交联反应,可顺利地制得氯甲基化聚苯乙烯(CCMPS)交联微球;控制交联反应的条件,如反应温度、反应时间、溶剂性质、催化剂种类与用量等,可获得交联度不同的微球,其球形度依然保持良好.     

薄层色谱、凝胶色谱、薄层扫描分析核-壳型微交联聚苯乙烯微粒

本文用薄层色谱成功地将微交联核-壳结构聚苯乙烯微粒中的少量线性PS分子与微交联组分相分离,用凝胶色谱法测得线性PS的分子量为104-105数量级;0.2-1.6×10-6g的点样量,薄层扫描吸收峰面积与样品量成良好的线性关系;可直接由峰面积计算线性PS分子的含量;结合微粒的表观粘度,对微粒的核-壳结构进行了定性分析。     

交联网络和浓溶液中高分子链运动的NMR研究：Ⅱ质子自旋—自旋？…

用自旋－自旋弛豫时间考察了线型聚苯乙烯溶液与溶胀交联聚丙烯酰胺－丙烯酸凝胶的质子弛豫行为。发现在溶胀交联体系中，不论交联度高低，聚丙烯酰胺－丙烯酸质子的弛豫时间弛豫都呈现出双指数衰减特征；而在线型溶液体系中，聚苯乙烯质子的弛豫时间弛豫符合单指数衰减特征。     

Inhomogeneity control in polymer gels

Inhomogeneities, that is, nonrelaxing frozen concentration fluctuations, are inevitably present in polymer gels because they are introduced during the crosslinking of the constituent polymer chains in a solvent. Therefore, inhomogeneities increase as the number of crosslinks increases in a gel. The ionization of polymer gels is one of the methods used to suppress inhomogeneities. However, because crosslinking also means a freezing‐in of the conformation and topology of polymer chains in a solvent according to the chemistry of crosslinking, inhomogeneity control is quite sophisticated. In this article, we discuss the relationship between the inhomogeneities and the molecular/environmental parameters of polymer gels, such as the polymer concentration, the degree of crosslinking, the degree of ionization, and the interaction parameter, by considering the memory effect of gels. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 617–628, 2005     

Synthesis of porous divinylbiphenyl copolymers and their sorptive properties towards phenol and its derivatives

Seven porous divinylbiphenyl polymers having the same nominal crosslinking degree (51.8 wt.%) have been synthesized using suspension polymerization method in the presence of the following inert diluents or their mixtures: toluene, heptane, dodecane, isooctane. The use of various inert diluents was aimed at changing the extent of polymeric network-diluent interactions. The obtained polymers have specific surface area in the range 50-300 m²/g depending on the type and amount of inert diluents used during polymerization. Their sorptive properties have been studied using dilute (0.5 mmol/l) aqueous solutions of phenol and its derivatives (2-chlorophenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,6-dimethylphenol, 4-hydroxyphenol). It has been found that sorption, at low equilibrium concentration, follows the order: 2,4,5-trichlorophenol > 2,4-dichlorophenol > 2-chlorophenol > 2,6-dimethylphenol > phenol > 4-hydroxyphenol. Full characteristic of the porous structure of polymers has been obtained by nitrogen adsorption at 77K.     

丙烯酰胺-丙烯酸交联共聚凝胶结构与分子运动的~1H NMR自旋晶格弛豫研究

用1HNMR方法测定了交联度分别为10％,7.5％，5％，25％，1％，0．5％及0．25％的丙烯酰胺-丙烯酸与N，N’－亚甲基双丙烯酰胺交联共聚水凝胶中水及主链质子的化学位移谱及自旋晶格弛豫时间T1，并用BBP模型进行了讨论。结果表明，水和凝胶主链的质子线宽随交联度加大而明显增宽，只有在低交联度下，由空间立规度造成的精细分裂才能呈现出来；水凝胶体系中水自旋晶格弛豫时间T1随交联度加大而非单调地减小，寓示凝胶内部有较强的键合束缚水存在，并满足双相快交换模型。聚合物主链质子T1与水质子的T1弛豫行为相反，随交联度加大主链运动受限加强而使其运动减慢，反映了聚合物主链的大分子运动特征，发现主链（-CH-）与（－CH2－）质子T1之比可表征凝胶内部分子链运动的强弱；讨论了NMR弛豫与凝胶孔径结构的关联。     

Basic study of the gelation of dimethacrylate‐type crosslinking agents

An investigation was made of the gelation of dimethacrylate‐type crosslinking agents in view of an application for separation media. The study mainly centered on a crosslinking agent, glycerol dimethacrylate (GDMA), which is relatively hydrophilic because of a hydroxyl group in the middle of its structure. The gelation of GDMA was compared with that of other hydrophobic crosslinking agents such as ethylene glycol dimethacrylate and 1,6‐hexanediol dimethacrylate. The diluents used in the study were toluene, toluene with methanol, and cyclohexanol. The gelation was observed in real time with a charge coupled device camera and dynamic light scattering (DLS). Also, the separated dry gels were extensively characterized with scanning electron microscopy, BET (N₂ absorption and desorption isotherm), and Fourier transform infrared. DLS analysis showed a stronger molecular interaction of GDMA gelation in toluene, whereas this interaction was much weaker in an alcoholic solvent such as toluene with methanol or cyclohexanol. This indicated that GDMA gelation might proceed through hydrogen bonding as well as a crosslinking reaction of vinyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 949–958, 2006     

Comparison of the sensitivity of 11 crosslinked hyaluronic acid gels to bovine testis hyaluronidase

Crosslinked hyaluronan gels are used in various applications where their stability is a prerequisite. The sensitivity of such gels to hyaluronidase can be determined as an index of stability by several approaches: chromatography, electrophoresis, and viscometry. We describe here a test based on the colorimetric determination of the N-acetyl-d-glucosamine released by hyaluronidase in standardized conditions. The sensitivities to bovine testicular hyaluronidase of 11 different gels used to fill skin wrinkles (Restylane; Perlane; Juvéderm 18, 24, 24HV, 30, and 30HV; Surgiderm 18, 24XP, 30, and 30XP) were compared.The method was reproducible, easy to perform, not time-consuming and allowed us to demonstrate that the sensitivity to testicular hyaluronidase was dependent on the degree of crosslinking of the gels and also on their monophasic/biphasic nature. Under our conditions, Surgiderm 30, 24XP and 30XP were the most resistant gels.We propose to retain the hyaluronidase test to predict the in situ stability of a crosslinked gel used to fill skin wrinkles.     

Assessment of nonrandom crosslinking in polymer networks by small-angle light scattering

The angle-dependent, isotropic light scattering exhibited by a diluent-swollen, ideal network is theoretically derived and compared with the light scattering exhibited experimentally by swollen real networks. In good diluents the difference is a measure of the spatial nonrandomness of the degree of crosslinking. A nonrandomness index (NRI) is introduced in terms of the Rayleigh ratios at zero scattering angle. A procedure is given for reliably obtaining the zero-angle Rayleigh ratio from experimental data at finite angles (2–30°). Measurements are reported for a series of poly(2-hydroxyethyl methacrylate) (PHEMA) networks, prepared at varying stages of dilution (in ethylene glycol, EG) and varying amounts of crosslinker (ethylene glycol dimethyacrylate, EGDMA). The theoretical Rayleigh ratios are calculated by employing the equilibrium degrees of swelling, refractive indices, and Young's moduli of the gels, measured in EG. The NRI is found to decrease upon decreasing the dilution during network formation and upon increasing the average crosslinking density. The NRI provides a probe of the network structure on a (sub)microscopic level. It is suggested that the NRI is closely correlated with the performance of elastomers under mechanical loading conditions.     

Sorption of textile dyes on β-cyclodextrin-epichlorhydrin gels

-Cyclodextrin (CD), hydroxypropyl -cyclodextrin (HPCD), poly(vinylalcohol) (PVOH) have been reacted with epichlorhydrin yielding different gels. The sorption capacity of the gels has been tested with acid, direct, mordant and reactive textile dyes as substrates, by the batch method. CD gels were more efficient than HPCD gels. No correlation has been observed between the performances of the CD gels and their respective crosslinking degree. The influence of pH is rather low whilst that of ionic strength is prominent on the sorption rate. The addition of anionic surfactants have either positive (CPA) or negative (SDS) effect on adsorption. The mechanism of sorption of dyes on gels could be physical adsorption in the polymer network and /or a host-guest inclusion complex formation     

Synthesis of Beaded Polyvinyl Alcohol by Suspension Methanolysis of Polyvinyl Acetate: Derivatization and Some Applications

A new procedure for the synthesis of porous and nonporous polyvinyl alcohol beads by controlled methanolysis of different concentrations of polyvinyl acetate suspension is described. By crosslinking with epichlorohydrin, insoluble crosslinked polyvinyl alcohol gels were obtained. These gels exhibit some peculiar swelling properties related to the reticulation degree, probably due to the interchain hydrogen associations. Crosslinked polyvinyl alcohol beads can be used as supports for liquid chromatography and for enzyme immobilization. Some new stationary phases for affinity chromatography and for ion-exchange chromatography were obtained. No substantial modifications in the catalytic properties of enzyme immobilized on crosslinked polyvinyl alcohol gels were established.     

高交联大孔苯乙烯-二乙烯苯共聚物的磺化反应

研究了高交联大孔苯乙烯－二乙烯本共聚物在有溶胀剂和无溶胀剂条件下,反应温度、 反应时间及共聚物合成时所用致孔剂对其磺化反应的影响．结果显示,当磺化反应在不同溶胀 剂介质中进行时,共聚物的交换容量随交联度变化可是现不同的关系．与低交联大孔共聚物（交 联度７％）比较,高文联大孔共聚物（交联度６０％）磺化反应速度更快,反应能在低得多的温度下 进行,同时溶胀介质对磺化产物的交换容量的影响变得很小．６０％交联的共聚物于３５Ｃ反应３ｈ, 可获得接近于表面磺化的产物．     

Interpenetrating Networks Obtained by Crosslinking in the Vinylacetate (VAc)-Triethoxyvinylsilane (VTES)-Tetraethoxysilane (TEOS) System

In the present work the sol-gel process in the ternary system VAc-VTES-TEOS was approached. The monomer that ensures the crosslinking of the obtained networks is VTES, which could react with VAc by free-radical polymerisation and with TEOS by hydrolysis-polycondensation. The early stage evolution of the process was monitored by gas chromatography coupled with mass spectrometry (GC-MS). The gels obtained were characterised by IR spectroscopy, DTA/TG analysis and DSC measurements. Important differences in the gelling process and in the properties of the obtained gels could be noticed, related to the presence of VAc and VTES in the reaction mixtures. The investigation allowed to establish the compositions and the experimental conditions in which gels with high degree of crosslinking could be obtained.