新型复合电流变材料的设计、制备及性能研究

【作者】 侯家祥；

【导师】 石磊；

【作者基本信息】 中国科学技术大学 ， 凝聚态物理， 2006， 博士

【摘要】 电流变液(Electrorheological Fluids简称ERF)是固体微颗粒在基液中组成的悬浮液(也可为均相液体，如液晶)。在外加电场作用下，它们的结构和性能表现出独有的特征，可在瞬间(千分之一秒左右)由液态转变成固态，其粘度陡然增大以至失去流动性。在电场作用下的电流变液表现出类似固体的行为，具有一定的屈服强度，且随外加场强增加，材料的强度增加，即性能可由外加电场连续调控。当外场撤除后材料迅速恢复到原来的状态。因而电流变液在液压系统、减振装置、印刷、光学以及机电一体化等领域显示出巨大的应用前景。然而，材料综合性能的不足，如剪切强度低、易沉降、温度效应显著等因素，严重地制约了电流变技术的工业化。通常认为电流变效应是由于电场作用下悬浮颗粒的极化，进而导致颗粒间相互作用的变化，使流体流变性能发生改变。 因此，根据介电极化理论，从电流变液材料物理设计的介电常数、电导率和介电损耗等参数出发，我们采用利用可控活性自由基聚合、溶胶凝胶方法，制备出两亲性高分子材料、聚合物／蒙脱土复合材料和核壳结构的新型电流变液材料。从分子水平上通过对材料的结构进行调节，以期获得对电流变材料性能的调控，从而为电流变材料的化学设计提供一种有效方法。 本论文的主要工作如下： 1．成功的通过四步反应，合成了链段中央带有ATRP引发基团的两亲性大分子引发剂。并以乙醇和THF混合体系为溶剂，CuBr／5，5，7，12，12，14-hexamethyl-1，4，8，11-tetraaza-macrocyclotetradecane为引发催化体系，使用得到的大分子引发剂引发St与二乙烯基苯(DVB)进行聚合，得到了纳米球。测试了制备出的新型聚合物电流变体的ER性质，通过比较可以发现，不同固体比例的电流变液在相同直流电场下，剪切应力表现出随着固体比例的增加而增加的趋势，这与悬浮型电流变流体的纤维化理论基本吻合。 2．用RAFT原位聚合方法使苯乙烯分别和丙烯腈以及聚苯乙烯-b-聚乙烯基吡啶在蒙脱土层间进行共聚，制备了聚苯乙烯-丙烯腈／蒙脱土和聚苯乙烯-b-聚乙烯基吡啶／蒙脱土纳米复合电流变材料。前者蒙脱土片层产生了剥离并且均匀分散在聚合物中，而后者为纳米插层材料。聚苯乙烯-b-聚乙烯基吡啶插入蒙脱土层后，在100Hz，30℃时，介电常数比蒙脱土提高了约45％，比纯PS-b-QP4VP更多还原

【Abstract】 Electrorheological fluids （ERF）, composed of small particles being dispersed in nonconductive liquids, are fascinating materials whose structure and rheological properties are dramatically altered by an external electric field. The rheological properties （viscosity, shear yield stress, shear modulus, etc.） of an ER suspension could reversibly change in several orders of magnitude under an external electric field of several kilovolts per millimeter. Since its mechanical properties can be easily controlled within a wide range almost from pure liquid to solid, the ER fluid could be used as various mechanical devices, such as clutches, valves, damping devices, and others areas, such as polishing, display, human muscle stimulator, and so on. Their potential wide utilization has stimulated a great deal of interests both in academic and industrial areas. Unfortunately, some available ER materials, some with relatively low shear stress and narrow operating temperature, some with poor suspension stability, are not satisfactory in engineering. Therefore, the development of high performance ER fluids via optimizing and tuning conducting materials has been a main subject of considerable interest for the application.Considering the influence of dielectric constant, conductivity and dielectric loss on electrorheological（ER） effects, an effective approach to prepare diblock copolymer, polymer/MMT nanocomposites and core-shell structure ER materials was proposed by controlled living radical polymerization method or sel-gel method. Based on this point, our aim to obtain the high performance materials should be carried out as well as the ER behavior be actualized through the chemistry design.All these facts are the origin and impetus of this thesis. The main results obtained in this thesis are as follows:1. A diblock copolymer, PEO-block-PMA, has been successfully prepared by atom transform radical polymerization with （CuBr/5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazamacrocyclotetradecane） and PEOOOCCHBrCH₂COOCH₂CH₂- OH as catalyst and initiator. And then the macro initiator is obtained by the reaction of PEO-b-PMA with BSA. Sub-micrometer sized micelles can be prepared by更多还原