热固性树脂中嵌段共聚物纳微尺度蠕虫结构的构筑及增韧研究

The certain drawbacks in fracture toughness substantially restricted the application of epoxy thermosets as reliable encapsulation materials. Recently developed nanostructured thermosets with wormlike morphology permits the increase in toughness, modulus and Tg. However, it's hard to achieve wormlike morphology because of nanostructures coalescence during matrix network formation. Prior study shows that curing has less influence on nanostructures templated by reactive block copolymers. In this fashion, the project proposed a strategy to toughen epoxy blends based on the concept of hierarchical structure. Through carefully designed reactive triblock copolymers, the nanostructures can be quenched before curing. The composition window between spherical micelles and vesicles enables the successful formation of nano/micro worm-like micelles in epoxy blends. The relationship and mechanism of hierarchical structure and performance of thermosets will be investigated. The hierarchical structure toughened epoxy thermosets with increased physical properties would like to provide theoretical foundation for novel encapsulation materials.

环氧热固性树脂缺口韧性差的缺点制约了其使用范围，影响到灌封器件的有效性和可靠性。近期研究发现，蠕虫状纳米结构改性环氧树脂可实现缺口韧性、模量与玻璃化温度同步提升，体现出显著优势。然而，蠕虫结构难以获得，原因是纳米结构在固化后易聚并。对此，申请人开展的初步研究表明引入反应性基团可减少固化剂与固化反应对微相形貌的影响。在此基础上，本项目从分子设计出发，制备反应性基团精确设计的嵌段共聚物。减少形成蠕虫结构的不利因素；结合嵌段结构的调节得到具有蠕虫结构的热固性树脂。利用其纳微多尺度特点，提高环氧树脂的缺口韧性、模量、耐热性，为制备新型特种灌封材料提供依据。

针对环氧热固性树脂缺口韧性差的缺点，项目设计了链段结构可控的对称反应性嵌段聚合物增韧剂。在链转移试剂二苄基三硫代碳酸酯（DBTTC）调控下，以苯乙烯、马来酸酐和丙烯酸正丁酯为单体，通过RAFT聚合合成了聚（苯乙烯-alt-马来酸酐）-b-聚丙烯酸正丁酯-b-聚（苯乙烯-alt-马来酸酐）（SMA-PnBA-SMA）。将SMA-PnBA-SMA与E51/MCDEA共混，得到了纳米结构改性的环氧热固性树脂。调控SMA-PnBA-SMA的嵌段结构，可以有效地控制基体中分散相的尺寸。进一步调节SMA含量，可以在环氧树脂基体中观察到短蠕虫结构。对共混物的性能表征表明，具有纳微多尺度特征的短蠕虫结构提高了环氧树脂的缺口韧性、模量和耐热性。