聚合物结构及氢键对共混聚合物的热导率调控及其机理研究

Nowadays, the thermally conductive and electrically insulating polymers are widely used as electronic packaging and electrical insulating materials. However, the thermal conductive particles filled polymers often show high thermal conductivity, as well as the reduced electrical resistivity, breakdown strength, deterioated mechanical properties, and inferior processing compared with pure polymer. In order to overcome these drawbacks, in this study, two kinds of polymers possessing interchain hydrogen bonding interactions, i.e., rigid and low-mass H-bond-accepting polymer, and high-mass H-bond-accepting polymer, were choosen as polymer pairs. The polymer blend film can be obtained through solution mixing by a spin-cast method, followed by thermally annealed at high temperature. By properly choosing the chemical structures of H-bond-capable moieties, the H-bond-accepting polymers and H-bond-donating polymer are required to be not only homogeneously dispersed, but also miscible at the molecular level to allow polymers to interwine within the radius of gyration, thus realizing a uniform and homogenegous distribution of H-bonds. The H-bond-accepting polymer transitions from a highly self-entangled state to a state in which the backbone is extended by means of the strong interchain interactions and the synergetic effect between interchains. The interwined chains begin to form local microscale ordered structure owing to the H-bonding self-assblemly behavior resulted from the templating effect of the rigid low-mass polymer. So, the thermal conductivity of polymer blend can be obviouly enhanced due to the thermal conductive paths formed from the local microscale ordered structure along polymer backbone and the homogeneous distribution interchain H-bonds network in the matrix ,which increases the phonon free path, suppresses the phonon scattering, leading to an enhanced thermal conduction. In this investigation, the effect of structure of H-bond-accepting polymer and H-bond-donating polymer on the interchain interactions, density and distribution of H-bonding will be discussed, and the dependence of the structure of polymer blend on the the H-bonding self-assblemly bahavior and the templating effect of rigid low-mass polymer will be exmained also. Based on the above results, the relations between the thermal conductivity and structures of polymer blend will be obtained, and the thermal conduction mechanism of the polymer blend with local microscale ordered structure will be revealed. The obtained results will provide new ideas and methods for the preparation of thermal conductive polymers with high electrical resistivity, breakdown strength, and good mechanical properties.

导热聚合物广泛用作电子封装及电气绝缘材料，填充型高导热聚合物存在绝缘电阻和电击穿强度低、力学性能下降及成型困难等问题。为克服上述缺陷，本研究选择两种能彼此形成氢键作用的聚合物：刚性短链聚合物A和长链聚合物B，采用溶液共混、旋转涂布及退火处理等过程制备共混聚合物。基于分子水平均匀混溶的聚合物分子链间的强氢键作用及链节协同效应使聚合物B长链从高度自缠结状态发生解缠、主链向舒展状态转变，借助于氢键自组装及短链聚合物的刚性主链模板效应，使分子链形成微尺度有序结构，利用分子链方向的微尺度有序结构和分子链间氢键网络提高共混聚合物导热性能。研究聚合物结构对氢键强度、密度及分布影响，探明氢键及分子链间协同效应、自组装行为对聚合物结构调控及其机理，建立聚合物热导率同分子链自组装行为及微结构之间关系，揭示微尺度有序结构聚合物的导热机理。为制备具备高绝缘及电击穿、良好力学性能的导热聚合物提高新的思路和方法。

导热聚合物广泛用作高频电子封装及高压电气绝缘材料，填充型导热聚合物的热导率的提升是以牺牲聚合物基体的优良介电强度及绝缘电阻为代价的，此外，复合材料还面临着力学性能下降及加工成型困难等问题。从聚合物结构上进行解耦调控，并实现协同提升其本征导热与介电强度是导热聚合物在基础研究及工业应用方面长期面临的严峻挑战。. 为协同提升聚合物的本征导热性能与介电强度，本研究选择了两种能彼此形成氢键作用的聚合物：刚性短链聚合物PAP和长链聚合物PVA及PAA等组成具有不同氢键作用大小的共混聚合物体系。首先合成了AP单体及不同分子量的PAP聚合物，然后和氢键给体聚合物采用溶液共混、旋转涂布及退火处理等过程制备了系列共混聚合物。基于分子水平均匀混溶的聚合物分子链间的强氢键作用及链节间的协同效应使氢键给体聚合物的长链从高度自缠结状态发生解缠、主链向舒展状态转变，借助于氢键自组装及短链聚合物的刚性主链模板效应，使分子链形成微尺度有序结构，利用分子链方向的微尺度有序结构和分子链间氢键网络提高了共混聚合物的导热性能，在最佳条件下PAP/PAA热导率最高达1.16W/(mK)，且具有很高的介电强度及很低的介电常数及损耗，以及低电导率及高绝缘电阻。本项目系统研究了聚合物结构对共混体系的氢键强度、密度及分布影响，探明氢键及分子链间协同效应、自组装行为对共混聚合物的微结构调控机理，诠释了聚合物热导率同分子链自组装行为及微结构之间关系，揭示了基于氢键网络结构的聚合物声子导热机理。此外，基于几类有机小分子在聚合物溶液形成不同结构及形态的有机晶体，利用形成的连续结构有机晶体构筑声子传递路径，提升聚合物的导热性能。. 本项目的研究结果为制备具备高绝缘及电击穿、良好力学性能的导热聚合物提高新的思路和方法。