基于超分子结构的成核剂成核聚甲醛结晶过程及成核机理研究

Controlling the crystallization of polyoxymethylene (POM) to improve the properties of POM through adding nucleating agent is an effective and practical way to balance the POM’s stiffness and toughness. A new inclusion complex nucleating agent would be synthesized through supermolecular host-guest recognization.The molecular architecture would be designed to adjust the compatibility of nucleating agent and POM in the melt by studying the kinetics of recognition reaction through temperature and reaction time control. Crystallization morphologies and non-isothermal crystallization kinetics of POM modified by nucleating agents would be studied by polarized optical microscopy and differential scanning calorimetry to understand the influence of inclusion complex on the crystallization behavior of POM. The molecular structure of highly effective nucleating agent would be determined by investigating the crystallization behaviors, crystallization morphologies and mechanical properties of POM nucleated with inclusion complex. The nucleating mechanism of effective nucleating agent would be understood by analyzing the single crystal structure of inclusion complex by wide angle x-ray scattering and transmission electron microscopy and discussing molecular interaction between host polymer and POM polymer chains to optimize the molecular structure of nucleating agent.

在聚甲醛改性研究中，通过改变聚甲醛的凝聚态构造，调节聚甲醛的晶体生长方式和结晶度，为聚甲醛的高性能化和提高韧性提供了一个有效途径本项目拟通过超分子主-客体识别合成一类新型高分子成核剂，通过探索超分子识别反应动力学，实现对高分子成核剂“嵌段”结构的精确控制，调控高分子成核剂与聚甲醛熔体间相容性。通过系统考察高分子成核剂对聚甲醛结晶行为的影响，构建高分子成核剂分子构造-聚甲醛凝聚态结构-材料性能的相互关系。解析高分子成核剂晶体结构，探讨高分子成核剂与聚甲醛分子间相互作用，揭示其成核机理并由此对高分子成核剂结构进行优化，制备聚甲醛高效专用成核剂。

本研究针对聚甲醛韧性差，热稳定性差的主要缺点，通过超分子主客体相互作用，设计和成了一系列不同客体分子与环糊精的包合物，并首次将包合物作为添加剂通过简单熔融共混制备了综合性能优异的聚甲醛复合材料。与传统聚甲醛改性剂相比，包合物由于其独有的超分子自组装结构，将两种或多种对聚甲醛具有增韧或增强效果的助剂通过非共价键力进行有效结合，形成具有特殊结构的包合物，既能实现助剂的均匀分散同时体现改性剂的多功能性：减小球晶尺寸，在增韧聚甲醛的同时提高其强度和模量并大幅度提高复合材料热稳定性。共混过程中包合物在聚甲醛基体中自组装成为“软壳-硬核”的阶层式结构，实现了复合材料的刚韧平衡。由于包合物合成方法简便易行且具有结构可调控性，有望成为高效多功能且具有普适性的聚合物改性剂在工业上获得广泛应用。