Isoprene Polymerization: Catalytic Performance of Iminopyridine Vanadium(III) Chloride versus Vanadium(III) Chloride

Mengmeng Zhao; Qaiser Mahmood; Chuyang Jing; Liang Wang; Guangqian Zhu; Xianhui Zhang; Qinggang Wang

doi:10.3390/polym11071122

Isoprene Polymerization: Catalytic Performance of Iminopyridine Vanadium(III) Chloride versus Vanadium(III) Chloride

Polymers (Basel). 2019 Jul 2;11(7):1122. doi: 10.3390/polym11071122.

Authors

Mengmeng Zhao¹, Qaiser Mahmood¹, Chuyang Jing^{1

2}, Liang Wang¹, Guangqian Zhu^{1

2}, Xianhui Zhang^{1

2}, Qinggang Wang^{3

4}

Affiliations

¹ Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266000, China.
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266000, China. wangqg@qibebt.ac.cn.
⁴ Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China. wangqg@qibebt.ac.cn.

Abstract

A series of vanadium complexes bearing iminopyridine bidentate ligands with various electronic and steric properties: V1 [CH₂Ph], V2 [CMe₂CH₂CMe₃], V3 [Ph] and V4 [2,6-ⁱPr₂Ph] were prepared and characterized by IR spectroscopy and microanalytical analysis. The catalytic capacity of all the complexes has been investigated for isoprene polymerization and was controlled by tuning the ligand structure with different N-alkyl and N-aryl groups. Activated by methylaluminoxane (MAO), the aryl-substituted complex V3 [Ph] exhibited high cis-1,4 selectivity (75%), and the resultant polymers had high molecular weights (M_n = 6.6 × 10⁴) and narrow molecular weight distributions (PDI = 2.3). This catalyst showed high activity up to 734.4 kg polymer (mol V)^-1 h^-1 with excellent thermostability even stable at 70 °C. Compared to the traditional VCl₃/MAO catalytic system, iminopyridine-supported V(III) catalysts displayed higher catalytic activities and changed the selectivity of monomer enchainment from trans-1,4 to cis-1,4.

Keywords: VCl3/MAO; Ziegler-Natta polymerization; iminopyridine ligands; polyisoprene; vanadium complexes.