η3‐π‐Allyl Acetoxyl Ni Complex, an Efficient Initiator for Synthesis of Hydroxyl‐Terminated Polybutadiene with High cis‐1,4 Unit Content.

A novel Ni‐based initiator is designed and synthesized for obtaining a hydroxyl‐terminated polybutadiene (HTPB) with higher cis‐1,4 unit content (≥90%). By investigating the effect of the butadiene skeleton structure and counterion on initiating efficiency, it is found that [η3‐Ni(CH2CHCHCH2OOCH3)][BPhF4] complex is a feasible combination to be used as an initiator. 1H‐NMR data prove that the initiator structure obtained is in accordance with the original design. The result of 1H‐NMR, 13C‐NMR, FT‐IR confirms that HTPB synthesized not only gains a significant amount in cis‐1,4 unit content (≥90%) compared with the HTPBs by free radical and anionic polymerizations, but also its molecular weight and molecular weight distribution can be effectively controlled during synthesis process. Because of the much higher cis‐1,4 unit content, the glass‐transition temperature of HTPB obtained via [η3‐Ni(CH2CHCHCH2OOCH3)][BPhF4] is markedly reduced; as a result, its low‐temperature mechanical property can also be significantly improved. A novel Ni‐based initiator Ni(CH2CHCHCH2OOCH3)][BPhF4] is designed and synthesized for obtaining a hydroxyl‐terminated polybutadiene (HTPB) with higher cis‐1,4 unit content (≥90%). The glass‐transition temperature of HTPB obtained via [η3‐Ni(CH2CHCHCH2OOCH3)][BPhF4] is markedly reduced; as a result, its low‐temperature mechanical property can also be significantly improved. [ABSTRACT FROM AUTHOR]