Ethylene-co-norbornene Copolymerization Using a Dual Catalyst System in the Presence of a Chain Transfer Agent.

Finizia Auriemma,Diego Sidari,Incoronata Tritto,Laura Boggioni,Rocco Di Girolamo,Claudio De Rosa,Simona Losio,Udo Stehling,Anna Malafronte

doi:10.3390/polym11030554

Abstract

Ethylene-co-norbornene copolymers were synthesized by a dual catalyst system at three concentrations of norbornene in the feed and variable amounts of ZnEt2, as a possible chain transfer agent. The dual catalyst system consists of two ansa-metallocenes, isopropyliden(η5-cyclopentadienyl)(η5-indenyl)zirconium dichloride (1) and isopropyliden(η5-3-methylcyclopentadienyl)(η5-fluorenyl)zirconium dichloride (2), activated with dimethylanilinium tetrakis(pentafluorophenyl)borate, in presence of TIBA. Values of norbornene content, molecular mass, glass transition temperature, and reactivity ratios r11 and r21 of copolymers prepared in the presence of 1+2 are intermediate between those of reference copolymers. The study of tensile and elastic properties of ethylene-co-norbornene copolymers (poly(E-co-N)s) gave evidence that copolymers were obtained in part through transfer of polymer chains between different transition metal sites. Mechanical properties are clearly different from those expected from a blend of the parent samples and reveal that copolymers obtained in the presence of 1+2 and ZnEt2 consist of a reactor blend of segmented chains produced by exchange from 2 to 1 and 1 to 2 acting as the ideal compatibilizer of chains produced by the chain transfer from 1 to 1, and from 2 to 2.

Highlights

Progress in polymerization catalysis has permitted the synthesis of olefin block copolymers.Tailored block copolymers are synthesized by sequential synthesis block by block through living polymerization catalysts [1,2,3]
ZnEt are rather brittle, and to widen their applications, we recently explored the effect of ZnEt2 as 2a as a potential chain transfer agent on the ethylene-norbornene copolymerization [33], by means
Catalyst precursors were activated by addition of dimethylanilinium tetrakis(pentafluorophenyl)borate, known to generate non-coordinating species in the activation process [40,41,42,43,44], and being appropriate for the study of the diethylzinc interactions with active catalytic species, where the presence of an intimate ion pair of the cationic zirconium species with a coordinating anionic species might decrease or even inhibit the chain transfer mechanism

Summary

Introduction

Tailored block copolymers are synthesized by sequential synthesis block by block through living polymerization catalysts [1,2,3]. They often provide materials whose mechanical properties are remarkable in comparison with those of homopolymer blends or random copolymers with the same chemical composition, because of microphase separation of the different blocks [1,2,4]. Living single-site olefin polymerization catalysts do exist. In a living polymerization system, there is no chain termination, only one chain can be grown per metal center of quite expensive catalysts [5,6].

Methods

Results

Conclusion