Synthesis of gradient copolymers through coordination insertion copolymerization is an unmet goal since the prerequisite is not only the copolymerization being performed in a living manner but also the composition drift being sensitive to the change of comonomer concentration. Herein, these challenging issues to ethylene/1-hexene polymerization were simultaneously solved by carefully tuning the steric of the ortho-substituent of the amine bis(phenolate) moiety within the corresponding titanium complex. The titanium complex 1 catalyzed ethylene/1-hexene copolymerization to give gradient copolymers P1–P4 within a certain range of 1-hexene concentrations through in situ polymerization and block copolymer P5 through a sequential feeding strategy. The structure–property relationship between the phase structure and the mechanical property and electric breakdown voltage were elucidated. Compared to P4 containing a tiny crystalline phase, the gradient copolymer P3 with a large discrete crystalline phase shows a much higher electric breakdown voltage (209.6 kV/mm vs 146.6 kV/mm) and tensile strength (23.6 MPa vs 3.8 MPa). With the accumulation of crystalline phase in P2, the electric breakdown voltage slightly decreases to 199.7 kV/mm, but the tensile strength improves to 34.0 MPa, which are similar to those of block copolymer P5 (E_b = 183.7 kV/mm, σ_b = 32.8 MPa) and superior to those of P1 (E_b = 160.7 kV/mm, σ_b = 25.9 MPa) with continuous crystalline phase.

中文翻译：

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通过原位共聚制备梯度乙烯/α-烯烃共聚物


通过配位插入共聚合成梯度共聚物是一个未实现的目标，因为前提条件不仅是以活生生的方式进行共聚，而且成分漂移对共聚单体浓度的变化敏感。在此，通过仔细调整相应钛配合物中胺双（酚酸酯）部分的邻位取代基的空间位位，同时解决了乙烯/1-己烯聚合的这些具有挑战性的问题。钛络合物 1 催化乙烯/1-己烯共聚，通过原位聚合在 1-己烯浓度的一定范围内得到梯度共聚物 P1-P4，并通过顺序进料策略得到嵌段共聚物 P5。阐明了相结构与机械性能和电击穿电压之间的结构-性能关系。与含有微小晶相的 P4 相比，具有大离散晶相的梯度共聚物 P3 显示出更高的击穿电压（209.6 kV/mm 对 146.6 kV/mm）和拉伸强度（23.6 MPa 对 3.8 MPa）。随着晶相在 P2 中的积累，电击穿电压略微降低至 199.7 kV/mm，但拉伸强度提高到 34.0 MPa，与嵌段共聚物 P5 （E_b = 183.7 kV/mm， σ_b = 32.8 MPa） 相近，优于连续晶相的 P1 （E_b = 160.7 kV/mm， σ_b = 25.9 MPa）。