SYNTHESIS OF ORGANOGERMANE OLIGOMERS VIA LIGAND SUBSTITUTION POLYMERIZATION FROM 1, 4-DIOXANE COMPLEX OF GERMANIUM DICHLORIDE

Some organogermanium oligomers with different side groups were synthesized via li-gand substitution polymerization from 1, 4-dioxane complex of germanium dichloride withdifferent organolithitum compounds. The oligomers were isolated through either precipi-tation from methanol or extraction using toluene with a yield of no less than 50%. Theweiglit average molecular weight (M_w) of the oligomers is ranging from 1.4×10~3 to 5.9×10~3depending on the type and alkyl length of the organolithium compounds used.     

Water absorption of a diglycidyl ether of bisphenol A/1,3-bisaminomethylcyclohexane (DGEBA/1,3-BAC) epoxy resin system

The diffusive and dynamic mechanical behavior of the DGEBA/1,3-BAC epoxy resin system was studied during water absorption. The diffusion of water was investigated at 100% relative humidity, by immersion of specimens in water at 60, 80 and 100°C. In all absorption experiments, water diffusion followed Fick's law. Diffusion coefficients and saturated water concentrations are given for these temperatures. The activation energy for diffusion was determined from the relationship between the diffusion coefficient and the reciprocal of the absolute temperature. The value obtained was 31.2 kJ mol^–1. Dynamic mechanical analysis of samples immersed in 100°C water and with various water contents showed both a shift of T_g, defined by thetan peak, to lower temperatures and a slight decrease in the dynamic modulus in the presence of water. These effects are probably a result of plasticization.This work was supported by the Xunta de Galicia through grant XUGA-17201A92.     

Degradation Kinetics of an Epoxy/Cycloaliphatic Amine Resin Under Isothermal and Non-isothermal Conditions

A study of an epoxy-cycloaliphatic amine system has been realized using a thermogravimetric technique (TG). Isothermal and non-isothermal (dynamic) methods were employed to determine the kinetic data of this system. Five methods were used for determining the activation energies of this system in the dynamic heating experiments. In two of them (Flynn-Wall-Ozawa, and Kissinger) it is not necessary to have a prior knowledge of the reaction mechanism of the degradation behaviour for this system. In the other ones (Coats and Redfern, Horowitz and Metzger, and Van Krevelen et al.) it is necessary to know this reaction mechanism, besides Criado et al. method was used for determining it. The results have shown that good agreement between the activation energies obtained from all methods can be achieved if it is assumed that the degradation behaviour of this system is of sigmoidal-rate type. This revised version was published online in August 2006 with corrections to the Cover Date.     

液体色谱,凝胶色谱分析低聚芳砜及其双烯大分子单体

本文用液相色谱和凝胶色谱对双酚A、双酚S型低聚芳砜及α,ω-双甲基丙烯酸聚芳砜酯大分子单体进行了组分分析,通过改合成条件、测定数均分子量等辅助手段确定液相色谱各峰的归属,计算其分子量及分子量分布指数,并对两种方法测定的结果进行了比较。用液相色谱观察低聚体每个组分的含量及其反应过程中的消长情况比凝胶色谱清晰。     

环状碳酸酯低聚物的合成及其开环聚合的研究

环状碳酸酯低聚物的合成及其开环聚合的研究陈雨萍魏玮李革（中国科学院化学研究所工程塑料国家重点实验室北京１０００８０）关键词环状碳酸酯低聚物，聚碳酸酯，开环聚合环状单体的开环聚合在合成高聚物方面具有突出的优点，即在聚合过程中没有副产物、热效应低、聚合...     

The pockels coefficient of new polymers for nonlinear optics and its time dependence after poling,compared with dielectric measurements

Epoxy polymers with donor–acceptor type side groups were synthesized for application in nonlinear optics. The stability of the Pockels coefficient was measured in thin films after poling. The relaxation times and their temperature dependence seem to be correlated with dielectric measurements. Guest–host systems (polystyrene and polymethylmethacrylate with dimethylaminonitrostilbene) were investigated for comparison.     

Regioselective hydrosilations. III. The synthesis and polymerization of ambifunctional silicon-containing epoxy monomers

Silicon-containing epoxide compounds bearing Si ? H groups can be readily prepared in high yields by the regioselective rhodium-catalyzed monohydrosilation of α,ω-dihydrogen functional siloxanes and silanes with vinyl epoxides. The remaining Si ? H groups in these compounds can be further selectively hydrosilated with unsaturated epoxides to give a series of unique ambifunctional monomers containing two different epoxide groups in the same molecule. The photopolymerization of these monomers has been studied using analytical techniques including real time infrared spectroscopy and differential scanning photocalorimetry. On photopolymerization, the new monomers yield interesting networks. © 1993 John Wiley & Sons, Inc.     

新型热反应大分子单体的合成与表征

溶液法合成了一些低分子量的羟端基低聚苯醚砜,并由相转移催化剂将之转为热反应大分子单体——α,ω-双甲基丙烯酸聚苯醚砜酯;用FTIR、~1H-NMR对其结构进行了表征,GPC、VPO对其分子量进行了分析和测定;用DSC、DTA对聚苯醚砜双烯大分子单体的转变温度、热反应过程进行了测定和分析。     

Study of the influence of isomerism on the curing properties of the epoxy system DGEBA (n=0)/1,2 DCH by DEA and MDSC

Summary Modulated differential scanning calorimetry (MDSC) and dielectric analysis (DEA) have been used to characterize the cure process of the system diglycidyl ether of bisphenol A (DGEBA(n=0)/1,2 diaminocyclohexane (1,2 DCH). The trans isomer and a mixture cis/trans(30-70% respectively) of 1,2 DCH were used to find their different behaviour. The study allowed to check the influence of the cisisomer on the thermoset curing process. Gelation times were obtained through the equation proposed by Johari and vitrification times from the point of inflection of the complex calorific capacity modulus.     

Mechanistic study of thermal behavior and combustion performance of epoxy resins: I homopolymerized TGDDM

Tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) undergoes homopolymerization on heating. Intramolecular reactions which compete with crosslinking favor the formation of cyclic structures with increasing thermal and fire resistance of the resin, whereas physical mechanical properties tend to decrease. The mechanism of thermal decomposition of TGDDM is studied by thermogravimetry, differential scanning calorimetry and thermal volatilization analysis with characterization of volatiles evolved and residue left. Thermal degradation of poly-(TGDDM) starts at 260°C with elimination of water from secondary alcoholic groups which is a typical pathway for epoxy resin degradation. Resulting unsaturations weaken bonds in the β-position and provoke the first chain breaking at allyl–amine and allyl–either bonds. With increasing temperature, saturated alkyl–ether bonds and alkyl carbon–carbon bonds are broken first, followed by the most stable alkyl–aryl bonds at T>365°C. The combustion performance of TGDDM is discussed on the basis of the thermal degradation behavior.