Half-titanocenes catalysts based on titamium-phosphinimide for producing atactic elastomeric polypropylenes with high molecular weight

Jian jun Chen*, Tie shi Wang, Zheng wei Tang, Yi bing Xu, Lin Xu, Mao sheng Cao, Zeng guo Feng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Two half-titanocenes, containing a phosphinimide ligand [(t-Bu)3P=N]CpTiCl2 (PT1) and [(t-Bu)3P=N]CpTiMe2 (PT2) as the main catalysts for olefin polymerization, were examined in propylene polymerization in the presence of methylaluminoxane (MAO) or [Ph3C][B(C6F5)4] as the co-catalyst. The catalytic performance was also compared with typical {rac-[En(IndH4)2]ZrC12} (1), CpTiCl3 (2) and Cp2TiCl2 (3) catalysts. The effects of experimental conditions, including feeding molar ratio of the co-catalyst to the main catalyst [Al]/[Ti], temperature, propylene pressure and reaction time, on the catalytic activity of the polymerization, the molecular weight and molecular weight distribution of the resulting polypropylenes (PPs) were investigated in detail. A maximal activity of 3.25 × 106 g PP/molTi·h was attained using PT2/[Ph3C][B(C6F5)4] in the presence of MAO at [Al]/[Ti] = 800. Meanwhile, a highest molecular weight of Mw = 4.42 × 105 with a molecular weight distribution of 1.73 was reached with PT1/MAO at [Al]/[Ti]=1200. The molecular weights were increased with decreased polymerization temperature, increased reaction pressure and polymerization time (tp). Interestingly, it was noted that an asymptotic plot of Mw versus tp was almost linear up to 15 min, indicating a “single-site” catalytic polymerization. 13C-NMR and IR analyses revealed that the resulting polymers were atactic PPs, which were more or less syndiotactically enriched atactic ones with higher diads r (62.28%) than m (37.72%). Furthermore, a calculated value of 1.04 for [mr/(2mm + mr)] + [mr/(2rr + mr)] indicated that the polymerization was conducted in agreement with the statistical model of Bernoullian. DSC measurements further confirmed the atactic microstructure of the PPs with a glass transition temperature (Tg) ranged from ?3.7 ºC to ?2.6 ºC without any melting endotherm. Accordingly, the PPs produced in this study by the phosphinimide catalysts were mainly made up of 1,2-insertion units together with a small number of 2,1-insertion units.

Original languageEnglish
Pages (from-to)1294-1303
Number of pages10
JournalActa Polymerica Sinica
Issue number8
DOIs
Publication statusPublished - 20 Aug 2017

Keywords

  • Half-titanocene
  • Phosphine nitrogen ligand
  • Propylene polymerization
  • Sequence distribution

Fingerprint

Dive into the research topics of 'Half-titanocenes catalysts based on titamium-phosphinimide for producing atactic elastomeric polypropylenes with high molecular weight'. Together they form a unique fingerprint.

Cite this