(Z)-1,3-pentadiene (Zp) exhibits a rigid planar molecular structure and is known for the typical 1,5-sigmatropic hydrogen shift, while it is commonly considered an inert monomer during polymerization. Herein, by utilizing the steric effect of the terminal methyl in Zp, the high trans-1,4-polypentadiene (HTPD) with highly ordered microstructure and well-defined sequence are successfully synthesized using barium dithymol/tert-butyllithium/tri-ethylaluminum trimetallic initiators based on anionic polymerization. The significant dependence of polymerization rate and trans-1,4-selectivity on ratio of Ba/Al/Li is demonstrated. The modification in microstructure (trans-1,4 content ranging from 75 % to 92 %) and stereo-regularity (isotactic triad mm% > 65 %) are confirmed by nuclear magnetic resonance (NMR). Compared with the poly((Z)-1,3-pentadiene) (PZp) prepared by n-BuLi containing σ-ligand modifiers, the strategy using a large steric initiator to achieve regular insertion of Zp into polymer chains is proved to be effective. Kinetics studies demonstrated that Ba–Al–Li system is characterized by retarded anionic polymerization (RAP), yet it shows a quasi-living process and enabling the preparation of stereometric block polymers such as polyisoprene-b-HTPD (PI-b-HTPD). Thermal performance analysis indicates that the obtained highly ordered polymers show superior thermoplastic properties (Tm = 77.4 °C) with crystallinity as an elastomer. Furthermore, reasonable interpretations for the structure formation, sequence, and rate reduction effected by the Ba/Al/Li trimetallic initiator are proposed.

中文翻译：

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使用 Ba/Al/Li 三金属引发剂对 （Z）-1,3-戊二烯进行阴离子聚合，合成结晶性高反式-1,4-聚戊二烯


（Z）-1,3-戊二烯 （Zp） 表现出刚性平面分子结构，以典型的 1,5-σ 氢转移而闻名，而它在聚合过程中通常被认为是惰性单体。在此，利用末端甲基在 Zp 中的空间位阻效应，使用基于阴离子聚合的二胸腺醇/叔丁基锂/三乙基铝三金属引发剂成功合成了具有高度有序微观结构和明确序列的高反式 1,4-聚戊二烯 （HTPD）。证明了聚合速率和 trans-1,4-选择性对 Ba/Al/Li 比率的显着依赖性。核磁共振 （NMR） 证实了微观结构（反式 1,4 含量范围为 75 % 至 92 %）和立体规则性（等规三联体 mm% > 65 %）的改变。与含有 σ-配体修饰剂的 n-BuLi 制备的聚（（Z）-1,3-戊二烯）（PZp） 相比，使用大空间位阻引发剂实现 Zp 规则插入聚合物链的策略被证明是有效的。动力学研究表明，Ba-Al-Li 系统的特点是延迟阴离子聚合 （RAP），但它显示出准生活过程，能够制备立体嵌段聚合物，例如聚异戊二烯-b-HTPD （PI-b-HTPD）。热性能分析表明，获得的高度有序聚合物表现出优异的热塑性性能 （Tm = 77.4 °C） 和弹性体的结晶度。此外，对 Ba/Al/Li 三金属引发剂对结构形成、序列和降速的影响提出了合理的解释。