【作者】 左瑞霖；

【导师】 梁国正；

【作者基本信息】 西北工业大学 ， 材料学， 2003， 博士

【摘要】 热固性液晶树脂兼具热固性树脂与液晶树脂两者的优点，其力学性能、耐热性、尺寸稳定性以及光电性能等均优于普通热固性树脂，成型工艺性等优于热塑性液晶聚合物，有望作为高性能树脂基体使用。热固性丙烯酸酯液晶树脂是最早开发的热固性液晶树脂之一，其相转变温度较低，溶解性较好，因此热固性丙烯酸酯液晶树脂比其它液晶树脂具有更好的应用前景。 目前国外对热固性丙烯酸酯液晶树脂虽已开展了大量研究，但对其力学性能的报道相对较少，某些热固性丙烯酸酯液晶树脂还存在耐热性低等缺点。本文针对高性能树脂基体的要求，合成了耐热性较高的无间隔链型热固性丙烯酸酯液晶树脂ME1、AE1以及短间隔链型热固性丙烯酸酯液晶树脂ME2、AE2，研究了树脂的合成、性能及影响因素，并对固化树脂的力学性能、耐热性进行了表征，对固化树脂结构与性能之间的关系进行了分析。结果表明，四种液晶树脂均具有预期的结构及良好的溶解性，其固化产物的介晶域具有较高的热稳定性。特别是ME2与AE2，其合成借鉴了环氧丙烯酸酯的合成路线，避免了传统路线原料贵、毒性大、步骤多、产率低等问题，其分子中存在短间隔链，克服了无间隔链型液晶树脂熔点过高的缺点，保持了较高的耐热性，赋予树脂以较高的韧性。与普通环氧丙烯酸酯树脂ME、AE相比，ME2、AE2的固化产物中存在介晶域，因此具有较高的冲击强度、弯曲强度、模量及耐热性。 热固性树脂普遍存在冲击强度低、韧性差等缺点，而目前常用的橡胶、热塑性树脂改性剂在提高树脂基体韧性的同时，却影响到体系的耐热性、模量、成型工艺性等性能。本文利用耐热性较高的热固性丙烯酸酯液晶树脂ME1、ME2对热固性树脂间苯二甲酸二烯丙酯(DAIP)进行增韧改性，研究了改性剂种类、用量以及固化工艺等对改性体系性能的影响，结果表明，改性体系在冲击强度改善的同时，弯曲强度、模量、耐热性等均有提高；提出热固性丙烯酸酯液晶树脂增韧DAIP的机理主要是刚性粒子的增韧作用以及原位复合自增韧作用。比较了相容性及初始相态对改性体系性能的影响，发现在制定改性体系固化工艺时，应同时考虑改性体系相容性、介晶域形成、反应性、固化温度之间的矛盾。 结合ME2对乙烯基酯树脂的改性以及ME1对聚甲基丙烯酸甲酯的改性研究，发现被改性树脂基体与改性剂之间相容性好、共聚程度高、改性剂含量低，均会妨碍相分离的进行、介晶域的生成，造成改性效果的降低。更多还原

【Abstract】 Thermoset liquid crystalline resin (TLCR) is a new material which has properties of both thermoset and liquid crystalline (LC). Its high mechanical strength and heat resistance, good dimensional stability and processability, excellent optical and electrical properties make it be promisingly used as a high-performance resin matrix. As a member of the family of TLCR, thermoset acrylate liquid crystalline resin (TALCR) has drawn much attentions compared to other TLCRs because of its low thermotropic transition temperature, good solubility in common solvents.Although studies on TALCRs have been conducting relatively longer, investigation on their mechanical properties remains a fewer. Some TALCRs also show low heat resistance due to the presence of long spacer. Besides, the present synthesis routes are involved in too much acryloylchloride and chloro-nol, which are either poisonous or expensive. With these considerations, four novel TALCRs are firstly designed and synthesized. Two of them are TALCRs without spacer, and the other two are TALCRs with short spacer. The latter are synthesized with a new route, which relies on the esterification of epoxy and acrylic acid. All TALCRs possess desired structure and good solubility in common solvents such as acetone. Most of them have mesogenic phase, which is proved with POM and DSC. At the same time, the factors influencing mesogenic phase are also discussed. Furthermore, mechanical properties and heat resistance of the cured resins are characterized with DMA, DTA, TGA and other related methods. Compared with the cured resins of common vinyl ester, the cured TALCRs have good performances with higher ’impact and bend strength, higher modulus and glass transition temperatures. It is the mesogenic phase in the cured TALCRs that contribute to these advantages over the common resins, and the presence of the mesogenic phase is characterized with SEM and WAXD.In’addition, thermosets often show low impact strength and poor fracture toughness, so it is desirable to improve their toughness. However, the present approaches to toughen thermosets such as incorporating reactive rubbers or thermoplastics to thermosets usually result in decrease of other properties, such as heat resistance, modulus and processability. For the first time, the TALCRs are used to toughen diallyl isophthalate (DAIP), and the factors influencing the properties such as type and content of modifier, curing procedure are discussed. With a great improvement of impact strength, the modified DAIPs also show the increase in bend strength, .modulus and heat resistance. Moreover, the toughness mechanism of the modified systems is studied with DMA, SEM and WAXD.Modification of vinyl ester (VE) and poly(methylmethacrylate) (PMMA) with TALCRs is also studied. Same as modified DAIP systems, these two modified systems are also characterized with above methods. It is found that good compatibility, high copolymerziation of modified systems and low content of modifiers can influence the phase-separation and the appearance of mesogenic phase, which may reduce the modifying effect.更多还原