交联型POSS/PU杂化体系的网络构建机制研究

Crosslinked inorganic/organic hybrid polymers which possessed excellent properties of both inorganic and organic materials had become one of the hotspots of the researches. The terminal properties of the polymer depended on the formation of the network during crosslinking process, however, the crosslinking process of this kind of polymers has not been investigated systematically and deeply due to the factors of distributions of crosslinking junctions and crosslinking densities. In this proposal, N-phenylaminomethyl POSS/PU with well dispersed crosslinking junctions and controllable crosslinking densities were investigated, and the small molecule organic crosslinking system was chosen as reference. (1) First, the character of the gel point was investigated by time- resolved mechanical spectroscopy. (2) A series of intermediate state was obtained by cancellation during the gelation process, rheology and SAXS was used to investigate the change of dynamic properties of the chain and the microstructure. (3) At last, low-field 1HNMR was introduced to analyze the content of different phase and the mobility of the chain during the crosslinking process, the crosslinking process was analyzed in molecule level. Based on the result of the rheology and NMR, the construction of network of POSS/PU was proposed, which will make the theoretical basis for investigating the crosslinking mechanism of crosslinked inorganic/organic polymers.

交联型有机无机杂化聚合物兼具了有机材料和无机材料的优良特性，已成为目前研究的一个热点。交联过程中网络结构的构建对聚合物最终性能的影响至关重要。然而由于交联中心分布以及交联密度难以控制，目前对该类聚合物交联过程系统深入的研究尚未开展。本项目选取交联中心分布均匀、交联密度可控的苯胺甲基POSS复合聚氨酯体系作为研究对象，并以小分子有机交联体系作为参比（1）首先利用时间分辨流变学对比分析其交联过程中凝胶点的特性；（2）进而通过反应淬灭在凝胶点前后得到一系列特殊中间态，并利用流变和SAXS分析其分子链动力学行为和微观结构的变化过程；（3）最后利用低场氢谱核磁共振分析其交联过程中不同组分含量以及链运动性的变化规律，从分子层面分析交联过程中结构的变化。结合流变和核磁分析结果，最终描绘出苯胺甲基POSS交联聚氨酯体系交联过程中网络的构建过程，为研究有机无机杂化交联聚合物的交联机制提供理论基础。

有机无机杂化交联型聚合物是一类新型交联体系，由于其兼具了无机填料和有机聚合物的特性，因而受到人们的广泛关注。聚合物发生交联时就会形成凝胶网络。凝胶时间在聚合物加工成型过程中的有着十分重要的意义。如果控制不好凝胶时间，就会出现爆聚等现象，从而极大地浪费了资源，增加了生产成本和时间。因此，监测交联体系在交联过程中的特性显得尤为重要。而在研究有机无机杂化交联型聚合物的交联特性过程中，由于涉及到交联中心的分布，交联密度的控制等因素使得该类体系的研究非常复杂，此外分析该类交联体系交联特性的有效手段也较少，致使目前对这类有机无机杂化交联体系交联特性的研究尚不多见。因此，选取一个理想的交联体系并利用一种有效的手段来研究其交联特性显得十分必要。. 本项目选取交联型的苯胺甲基POSS复合聚氨酯(POSS/PU)体系作为研究对象。利用流变学首先对交联体系的交联过程进行研究，进而得知网络生长过程信息；在此基础上利用Winter-Chambon准则分析出体系在不同交联条件下的凝胶点，并研究交联体系在凝胶点的特性；最终根据不同交联条件制备一系列交联型POSS/PU，从微观形貌和性能上对制备的材料进行分析。研究表明当POSS含量在2.5%-6% 之间时，材料具有自相似性。TEM进一步表明在此区间内，POSS几乎纳米级别分散。继续提高POSS含量会导致POSS的聚集效应。该方法为制备过程可控、性能优异的纳米交联型聚合物提供技术支持，为研究有机无机杂化交联体系的凝胶化特征行为提供理论依据。