Studies on chain shuttling polymerization reaction of nonbridged half-titanocene and bis(phenoxy-imine) Zr binary catalyst system.

Qinwen Xu,Rong Gao,Dongbing Liu

doi:10.1098/rsos.182007

Abstract

In this contribution, olefin block copolymers were produced via chain shuttling polymerization (CSP), using a new combination of catalysts and a chain shuttling agent (CSA) diethylzinc (ZnEt2). The binary catalyst system included nonbridged half-titanocene catalyst, Cp*TiCl2(O-2,6-iPr2C6H3) (Cat A) and bis(phenoxy-imine) zirconium, {η2-1-[C(H)=NC6H11]-2-O-3-tBu-C6H3}2ZrCl2 (Cat B), as well as co-catalyst methylaluminoxane (MAO). In contrast to dual-catalyst system in the absence of CSA, the blocky structure was obtained in the presence of CSA and rationalized from rheological studies. The binary catalyst system could cause the CSP reaction to occur in the presence of CSA ZnEt2, which yielded broad distribution ethylene/1-octene copolymers (Mw/Mn: 35.86) containing block polymer chains with high Mw. The presented dual-catalytic system was applied for the first time in CSP and has a potential to be extended to produce a library of olefin block copolymers that can be used as advanced additives for thermoplastics.

Highlights

Chain shuttling polymerization (CSP) process involves the shuttling of growing polymer chains via a chain shuttling agent (CSA) between two catalyst active sites, which efficiently prepare block polymers
The results of ethylene polymerization using either composed of nonbridged halftitanocene (Cat A) or Cat B, and the CSA ZnEt2 are listed in table 1 (Runs 1– 4)
In the case of the individual catalyst in the presence of ZnEt2, there was a significant decrease in molecular weight and a little decrease in molecular weight distribution compared to the dual-catalyst system (Cat A þ Cat B)/MAO (Run 2, Run 4 versus Run 5 in figure 1)

Summary

Introduction

Chain shuttling polymerization (CSP) process involves the shuttling of growing polymer chains via a chain shuttling agent (CSA) between two catalyst active sites, which efficiently prepare block polymers. CSP is based on reversible chain transfer reactions, including catalyzed chain growth [1,2] and coordinative chain transfer polymerization [3,4,5]. According to the literatures reported by Valente et al [6] and Zinck [7], CSP catalysts can be selected from FI catalyst, pyridylamide catalyst, a-diimine catalyst, rare earth catalyst and metallocene catalyst. 6: 182007 Ti O Cl Cl N ZrCl2 O2 Cat A tBu Cat B. Structures of the nonbridged half-titanocene complex (Cat A) and bis( phenoxy-imine) zirconium complex (Cat B)

Methods

Results

Conclusion