Olefin block copolymer is one class of promising high-end material that has the potential to combine the performance advantages of individual blocks. In this work, a series of isotactic polypropylene (PP)-based diblock copolymers was designed and synthesized by coordinative chain transfer polymerization using a dimethyl(pyridylamido)hafnium/[PhC][B(CF)]/AlBu catalytic system. The prepared diblock copolymers were composed of the regular PP segments and the propylene/1,5-hexadiene (1,5-HD) random segments. The incorporated 1,5-HD existed exclusively as methylene-1,3-cyclopentane units in the polymer chains, because of the complete cyclization selectivity of the employed dimethyl(pyridylamido)hafnium catalyst. These block copolymers possessed high melting temperatures over 158 °C. Moreover, the block copolymers exhibited remarkably improved mechanical properties with respect to PP, which could be systematically tuned by adjusting the content of 1,5-HD. In the 1,5-HD content range of 3.4–11.0 mol%, the block copolymers exhibited both high yield stress and high elongations at break. The copolymerization approach of block copolymers provided an effective method to achieve the strength-ductility balance of PP-based copolymers.

中文翻译：

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含环状单元的等规聚丙烯嵌段共聚物的制备及表征

烯烃嵌段共聚物是一类有前途的高端材料，有潜力结合各个嵌段的性能优势。在这项工作中，使用二甲基(吡啶氨基)铪/[PhC][B(CF)]/AlBu催化体系通过配位链转移聚合设计并合成了一系列等规聚丙烯(PP)基二嵌段共聚物。制备的二嵌段共聚物由规则的PP链段和丙烯/1,5-己二烯(1,5-HD)无规链段组成。由于所采用的二甲基（吡啶酰氨基）铪催化剂具有完全环化选择性，因此掺入的 1,5-HD 仅以亚甲基-1,3-环戊烷单元的形式存在于聚合物链中。这些嵌段共聚物具有超过 158 °C 的高熔融温度。此外，嵌段共聚物相对于PP表现出显着改善的机械性能，可以通过调整1,5-HD的含量来系统地调节机械性能。在 1,5-HD 含量范围为 3.4–11.0 mol% 时，嵌段共聚物表现出高屈服应力和高断裂伸长率。嵌段共聚物的共聚方法为实现PP基共聚物的强度-延展性平衡提供了有效的方法。