一种古老而又年轻的天然高分子—杜仲胶

本文简述了杜仲胶的开发史及资源情况。指出,杜仲胶高弹性体的出现,是其研究开发进入新阶段的标志。指出临界交联度是杜仲胶获得高弹性的关键概念。这种由有序柔性链组成的大分子网络,其高弹性不宜用分子链无规线团的贡献来解释,而是由于大分子网络的整体无序性。     

交联网络和浓溶液中高分子链运动的NMR研究Ⅲ.质子自旋-晶格弛豫时间与凝胶和浓溶液体系中高分子链段的运动

用自旋－晶格弛豫时间（Ｔ１）研究了溶胀的交联聚丙烯酰胺－丙烯酸网络和线型聚苯乙烯溶液中质子的弛豫行为。交联网络中，随着交联度增大，Ｔ１ＣＨ／Ｔ１ＣＨ２的值由１．１７逐渐趋近于１；而线型聚苯乙烯溶液中，Ｔ１ＣＨ／Ｔ１ＣＨ２的值由最稀浓度下的１．７过渡到１。说明在交联网络中，交联度很低时，链段的运动已经相当受约束；但交联度很大时，充分溶胀的交联网络中链段运动仍有一定自由度。而在线型高分子浓溶液中，链段的运动严重受阻，导致自旋扩散效应非常完全，彻底平均掉了各质子间Ｔ１时间的差异。     

杜仲胶研究新进展

本文从和天然橡胶对比开始,对杜仲胶作了简要介绍;根据杜仲胶链结构的三大特征:双键,柔性及反式链结构,及其在橡胶一塑料材料谱中的特殊位置,对杜仲胶结构与性能的关系进行了讨论,作者指出:由于杜仲胶硫化过程三阶段特征的揭示,而通过与橡胶,塑料进行多途径共混,又可获得广性能的材料,从而使杜仲胶研究进入材料工程学新阶段。文中用图示描述了杜仲胶硫化弹性网络的非无规线团模型,并指出:其弹性来自分布于整个网络中各交联点的备向同性构象记忆。     

交联网络和浓溶液中高分子链运动的NMR研究 Ⅱ质子自旋-自旋弛豫与凝胶和浓溶液体系中高分子链段运动

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。说明在线性聚苯乙烯溶液中，高分子的链段运动是一种均匀行为，而在溶胀交联聚丙烯酰胺－丙烯酸体系中，不论交联度高低，高分子链段运动始终存在快慢不同的两部分。     

同步辐射显微红外光谱法应用于杜仲的研究

同步辐射显微红外光谱具有高亮度、高信噪比等优势.应用同步辐射显微红外光谱对于中药进行研究,可以进行微区分析,从而更加深入了解中药的组成.应用同步辐射显微红外光谱对于杜仲的冰冻切片进行研究,采集不同微区的一系列红外光谱;同时对选定区域进行化学成像,进一步研究该区域中化学组成的分布,从而对于杜仲红外光谱中各个峰的归属有深入...     

醋酸纤维素／聚乙烯基吡咯烷酮共混体系的特殊相互作用表征（Ⅱ）

通过测定醋酸纤维素（ＣＤＡ）和聚乙烯基吡咯烷酮（ＰＶＰ）共混物溶液的绝对粘度和特性粘数，发现ＣＤＡ和ＰＶＰ分子链段间有缔合现象．用富里哀变换红外光谱（ＦＴＩＲ）研究了共混物的吸收光谱，发现共混物中ＣＤＡ的羟基吸收峰和ＰＶＰ的羰基吸收峰均向低频方向迁移，证明了ＣＤＡ的羟基和ＰＶＰ的羰基之间有氢键形成．研究结果表明ＣＤＡ和ＰＶＰ的相容性及其特殊相互作用来源于不同分子链段间的氢键相互作用．     

交联网络和浓溶液中高分子链运动的NMR研究：I.NMR质子线型分析

用质子ＮＭＲ谱对交联凝胶高分子（聚丙烯酰胺－丙烯酸）网络与线型高分子（聚苯乙烯）浓溶液体系的ＮＭＲ线型进行了比较研究，结果表明，两种体系中高分子链段运动具有不同的特征。在充分溶胀的交联凝结胶高人子网络中，交联点间的链段运动比较自由，交联点的运动则比较慢，使其质子谱呈现“超洛伦兹”线型；而在线型高分子浓溶液中，缠结点间链段与缠结点一样，运动并不自由，使谱线呈现出类似固体的宽线宽的高斯线型。     

尼龙6升温过程的二维红外相关分析研究

通过二维红外相关分析来研究尼龙6在25～200℃范围内酰胺氢键和碳氢链段的结构变化．结果证明，尼龙6中酰胺氢键的吸收峰和主链上亚甲基的伸缩振动对于温度变化所导致的结构变化是十分敏感的，因此可以通过对二维红外相关谱图的分析，确定尼龙6在升温过程中酰胺氢键的解离和碳氢链段结构变化的先后顺序．     

红外光谱法研究交联淀粉的退化行为

用红外光谱研究了交联淀粉的退化过程, 结果表明, 交联淀粉具有与原淀粉大分子类似的退化过程, 即淀粉大分子临近的链段间形成双螺旋局部有序化结构, 再进一步规则地排列成结晶有序的结构. 由于交联键的限制, 交联淀粉的有序化过程相对较慢、 程度较低, 而且当交联度过高时无法形成结晶结构.     

结晶聚合物品相相容性的研究

通过ＤＳＣ、Ｘ－射线衍射、红外光谱及拉伸试验研究了ＨＤＰＥ与ＬＬＤＰＥ、ＨＤＰＥ与ＬＤＰＥ之间的晶相相容性．结果表明，链结构相近的ＨＤＰＥ和ＬＬＤＰＥ的晶相相容性好，能形成共晶；而链结构差异较大的ＨＤＰＥ和ＬＤＰＥ的晶相相容性较差，倾向于分别结晶，但有部分链段被对方的晶区夹持．不论是支化度大的ＬＤＰＥ链段插入以ＨＤＰＥ为主的晶区，还是支化度小的ＨＤＰＥ链段插入以ＬＤＰＥ为主的晶区，都可破坏晶区的规整性．共晶的形成使共混物的熔点、结晶度、晶粒体积等低于两组份的线性加和，而力学性能，尤其是断裂伸长率，则显著提高，呈协同效应．     

Thermoxidative Decomposition of Some Polysulfones under Dynamic Conditions of Heating

Kinetic aspects of the first step of thermoxidative decomposition, under dynamic conditions of heating, of some polysulfones have been studied. The dependence of the kinetic parameters on the heating rate and conversion degree has been established. The compensation effect and conversion function have also been discussed. Polysulfone decomposes by the breaking of the main chain, a process involving very high activation energy. Chemically modified polysulfones show the first step of thermoxidative decomposition at relatively low temperatures. This step corresponds to the elimination of functional side - groups for the bromomethylated polysulfone while in the case of the carboxylated polysolfone, the loss of the carboxyl group is probably accompanied by a crosslinking reaction. This revised version was published online in July 2006 with corrections to the Cover Date.     

采用重复互贯聚合用废弃白球末合成凝胶型阳离子交换树脂的研究

采用重复互贯聚合工艺将废弃白球末加入单体－交联剂－引发剂体系中充分溶胀，再按照常规悬浮聚合和磺化反应工艺合成凝胶型阳离子交换树脂，结果显示，细粒度白球的交联度在4％－7％，单体吸收比为100％，采用盐水滴加工艺保证单体在白球中的均匀扩散和吸收，所合成的阳树脂的各项性能指标均国家标准，这种重复互贯聚合白球与相同交联度的普通白球比较，具有较高的磺化反应活性，较高的交联度，湿真密度，湿视密度和较高的交换容量。     

Long term environmental effects on physical properties of vinylester composite pipes

Glass fiber reinforced vinylester pipes (GFRP) have been exposed to outdoor conditions for 60 months. The effect of the outdoor exposure on the glass transition temperature (Tg) and the crosslinking index is discussed. The Tg and the degree of crosslinking has been determined using differential scanning calorimetry (DSC). DSC has become a preferred technique for rapid determination of transition temperatures and crosslinking for pure polymers, however, the use of this technique for composites is quite complex. This complexity arises from the fact that, in addition to the temperature overlap between the Tg and that of the crosslinking range, the amount of glass fibers in the GFRP is not constant. For this reason, a special measuring technique has been developed for the measurement of the amount of crosslinking of GFRP material. In this paper, it is illustrated that the DSC results clearly show the glass transition temperature and the exothermic crosslinking reaction of the vinylester composites. The results show that the glass transition temperature of the vinylester rapidly increases with respect to exposure time up to 12 months and then slightly decreases for longer exposure times. Similar trends were also observed for the change of the degree of crosslinking. The outdoor environment has also affected the weight of the exposed GFRP samples. It is observed that the weight of GFRP has gradually decreased with the exposure time. These physical changes of Tg, crosslinking and weight have impact on the tensile strength of the GFRP. For the initial outdoor exposure up to 24 months there is a 12% increase in strength from 250 MPa to 280 MPa. This increase is attributed to about 12% increase in crosslinking of the GFRP. However, for longer exposure the tensile strength has decreased back to 250 MPa due to slight decrease in crosslinking and small reduction of weight. It is observed that most of the weight loss has taken place at the surface of the GFRP samples.     

Synthesis and characterization of new polyimides containing ethynylene linkages

We have synthesized a series of new diamines containing bis(ethynylaniline) linkages by bromine substitution reaction of ethynylaniline with 4,4′-bis(4-bromophthalimido)diphenylether (PODA) or 1,4-bis(4-bromophthalimido)benzene (PPDA). The intermediates were separated at each step, purified and characterized by the spectroscopic techniques. The model compound having imide and triple bond moiety was synthesized in order to elucidate the nature of the products formed from the ethynyl curing by FT-IR spectroscopy. The polymerization reaction of ethynylaniline diamines with various dianhydrides gave fully imidized and soluble aromatic polyimides. The thermally cured polyimide samples displayed good solvent resistance. The thermal crosslinking of triple bond moieties in the main chain was carried out by heating in the temperature range from 150 to 400 °C. The glass transition temperature of polyimide completely disappeared after heat treatment at 400 °C for 5 min. The polyimides derived from diamines containing bis(ethynylaniline) groups were thermally stable after heat treatment.     

Sequential crosslinking for mechanical property development in high sulfur content composites

This report details how sequential crosslinking processes can be applied to develop properties in sulfur-bisphenol A composites. Olefinic carbons were first crosslinked by inverse vulcanization (InV) at 180°C and then aryl carbon crosslinking was affected via radical-induced aryl halide-sulfur polymerization (RASP) at 220°C. To demonstrate that these two crosslinking mechanisms are orthogonal and can be used to affect stepwise property changes, O,O′-diallyl-2,2′,5,5′-tetrabromobisphenol A was selected as a comonomer. After InV of the monomer with 90 wt% sulfur, a flexible plastic material having an elongation at break of 89% was obtained, whereas after heating this premade polymer to initiate RASP, the polymer develops a threefold increase in its tensile strength and has an elongation at break of only 29%. The sequential crosslinking strategy demonstrated herein thus provides an innovative approach to tuning the properties of high sulfur-content materials.     

Injectable Hyaluronic Acid/Poly(γ-glutamic acid) Hydrogel with Step-by-step Tunable Properties for Soft Tissue Engineering

Injectable hydrogels as an important class of biomaterials have gained much attention in tissue engineering. However, their crosslinking degree is difficult to be controlled after being injected into body. As we all know, the crosslinking degree strongly influences the physicochemical properties of hydrogels. Therefore, developing an injectable hydrogel with tunable crosslinking degree in vivo is important for tissue engineering. Herein, we present a dual crosslinking strategy to prepare injectable hydrogels with step-by-step tunable crosslinking degree using Schiff base reaction and photopolymerization. The developed hyaluronic acid/poly(γ-glutamic acid)(HA/γ-PGA) hydrogels exhibit step-bystep tunable swelling behavior, enzymatic degradation behavior and mechanical properties. Mechanical performance tests show that the storage moduli of HA/γ-PGA hydrogels are all less than 2000 Pa and the compressive moduli are in kilopascal, which have a good match with soft tissue. In addition, NIH 3 T3 cells encapsulated in HA/γ-PGA hydrogel exhibit a high cell viability, indicating a good cytocompatibility of HA/γ-PGA hydrogel.Therefore, the developed HA/γ-PGA hydrogel as an injectable biomaterial has a good potential in soft tissue engineering.     

Amphiphilic sorbents based on polysiloxanes crosslinked by an N,N′‐heterocycle

New amphiphilic sorbents have been synthesized by crosslinking of the chloromethyl side‐functionalized polysiloxanes with piperazine. Three structures, differing by the crosslinking degree, have been synthesized as potential sensitive materials for humidity sensors able to work at high humidity or as metal sorbents. Correlations between structure and morphology of the polymeric matrix, as well as their swelling capacity in solvents with different polarities, are discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Computational synthesis,structure, and glass transition of (1,4) Cis‐polyisoprene‐based nanocomposite by multiscale modeling

The main goal of the present study was to produce insights from the atomistic modeling into the structural changes in elastomer‐based polymer nanocomposites caused by the surface modifications of the filler particles, and by the crosslinking of the participating polymer matrix. The fully atomistic molecular‐dynamics computer simulations of crosslinked (1,4) cis‐polyisoprene (PI) films capped by amorphous silica substrates was set‐up, in the presence of realistic coupling and covering agents. The PI film stratified structure has been studied in the proximity of the corresponding glass transition, by varying the degree of crosslinking and the PI film thickness. Some monomer ordering induced by the pristine (bare) silica disappeared almost completely in films with modified surfaces. The average monomer density increased with degree of crosslinking. As compared with PI bulk, the glass‐transition temperature was slightly larger for highly crosslinked PI films with bare silica and surfaces with coupling agents, and increased with increasing confinement. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 473–485     

Synthesis and Physicochemical Properties of Hypercrosslinked Polysterene Restricted-Access Materials

With a view to simplifying and reducing the cost of the synthesis of novel selective restricted-access materials based on microporous hypercrosslinked polystyrene for solid-phase extraction, various polystyrene crosslinking agents and Friedel–Crafts catalysts in various combinations have been studied. It has been found that the most effective crosslinking agent is monochlorodimethyl ether; in addition, expensive tin chloride has been effectively replaced with a smaller amount of cheap ferric chloride. Under special conditions for the suspension copolymerization of styrene with 1, 2, and 3% of divinylbenzene, copolymers with a bead size of 30–70 μm have been synthesized. Each of the copolymers has been further crosslinked with monochlorodimethyl ether to a degree of crosslinking of 100, 150, and 200%. These polymers are porous materials swellable in water and any organic solvents. The hypercrosslinked polymer network is not accessible to large molecules of proteins (Cytochrome C and albumin) and does not cause protein adsorption; owing to this feature, the sorbents can be classified as novel selective restricted-access materials.