采用不同的测试方法，对双酚A型苯并■嗪和两种苯并■嗪模型化合物热聚合体系固化过程中的体积变化从表观体积收缩率、密度-固化时间曲线、恒温固化收缩率以及密度-温度曲线几方面进行了研究，深入探讨了苯并■嗪在固化过程中是否发生体积膨胀，并着重讨论了不同酚核结构苯并■嗪开环聚合过程中体积变化的差异及影响因素。结果表明，同结构的苯并■嗪均呈现出宏观体积膨胀效应，但在恒温固化过程中却均呈现体积收缩，且这种体积变化的大小与苯并■嗪的分子结构、聚合反应程度和交联密度相关。

以苯酚、苯胺和甲醛为原料，合成了三种不同结构的低粘度苯并噁嗪中间体树脂。根据RTM成型工艺中注塑和成型过程对基体树脂的特殊要求和不同组分的反应活性，系统研究了树脂粘度和凝胶化时间与温度的关系，及玻璃布层压板的力学性能和耐热性，详细讨论了树脂组成和催化剂种类及用量的影响。结果表明，以有机酸或环氧-叔胺为催化剂，以低粘度苯并口恶嗪树脂为主体所构成的多组分树脂体系，是一类可用于RTM成型工艺的新型树脂；该类树脂基复合材料可用做耐高温结构材料在155℃长期使用。

The structures and properties of benzoxazines were investigated by virtue of molecular modeling at a molecular level. By means of Cerius software (versopm 4.0) supplied by Molecular Simulations Ine., the molecular mechanies and the molecular dynamies were performed under a PCFF force field. Five kinds of the polymeric chains of benzoxazines were ereated by using polymer builder and energy minimization, The relaxation process was conducted with both energy minimization and molecular dynamies.

A novel polyimide (PI) containing pendent biphenyl ester groups was synthesized from 3, 52 diaminobenzoic-4'-biphenyl ester (DABBE) and 3, 3', 4, 4'-oxydiphthalic dianhydride (ODPA) by a one-step hightemperature polycondensation in m-cresol. This PI is a semicrystalline polymer. Lots of short fine fibric crystals with length and diameter about 20μm and 1μm respectively disperse randomly in the PI film. The optical textures and the X-ray diffraction patterns of the PI solution and film show that the PI main chains are in the extended conformation and pack parallel to each other, and the pendent biphenyl ester groups occupy the space between the main chain layers, more or less perpendicular to the main chains. At the same time, mechanical and thermally stable properties of the PI film were investigated. The excellent mechanical properties of general polyimide films are reasonably maintained, the polyimide filmwith pendent groups showes higher tensile strength and modulus and lower Tg. TGA study showes a typical two-step weight loss behavior corresponding to the pyrolysis of pendent groups and main chains of the PI, respectively.

This is a part of our systematic research work on polyimides with mesogenic unit side chain. In this study, a new 4'-phenylphenyl 4-(3", 5"-diaminobenzoyloxy) benzoate and polyimide were synthesized, and characterized by FTIR, 1H-NMR, inherent viscosity, mechanical properties, and solubility measurements. The diamine composed with mesogenic unit aryl ester groups and biphenyl group with longer L/D ratio, was synthesized by two key steps. Firstly, the hydroxyl group of 4-hydroxybenzoic acid was protected by acetoxy group for avoiding self-polymerization of 4-hydroxybenzoic acid, and then selectively hydrolyzed after esterification of carboxyl. Secondly, a selective catalysis hydrogenation was adopted to prevent the aryl ester from deoxidation. Based on this diamine, a novel polyimide was prepared by polycondensation of 4'-phenylphenyl 4-(3", 5"-diaminobenzoyloxy)benzoate and 4-aminophenyl ether(ODA) with 4, 4'-oxydiphthalic anhydride(ODPA) in N-methyl-2-pyrrolidone (NMP). The resulting polyimide with longer side chain showed better solubility and more regular structure. Its inherent viscosity is lower than that without side chains, but its modulus and strength not only maintained, even improved.