Engineering Poly(ethylene-co-1-butene) through Modulating the Active Species by Alkylaluminum

Abstract

A SiO 2 /MgCl 2 -bisupported Ziegler-Natta type catalyst is studied in gas phase ethylene/1-butene copolymerization. With a minimal amount of alkylaluminum required to activate the catalyst, polymerization kinetics is profoundly affected by the dosage of it. High dosage of alkylaluminum retards the polymerization but does not kill the catalyst. Through a comprehensive characterization on the samples by DSC, CEF, TGIC, CFC and NMR, it has been showed that alkylaluminum also alters the short chain branching distribution (SCBD) of the copolymer but barely affects the total comonomer incorporation. It is proposed that alkylaluminum alters the active species from producing statistical copolymer chains to producing block polymer chains with C4-enriched and C4-scattered segments. It provides an example of bimetallic structure of active species as well as an approach to tailoring SCBD between statistical copolymer and block copolymer bearing C4-enriched and C4-scattered segments.

Exploring cocatalyst type effect on the Ziegler–Natta catalyzed ethylene polymerizations: experimental and DFT studies

“…Indeed, after the catalyst, the selection of the appropriate cocatalyst is the most important and effective parameter in olefin polymerization processes [10]. The type of cocatalyst not only affects catalyst productivity but also alters the microstructure and arrangement of monomers in polymer chains during the polymerization reaction [11,12]. It is well-known that, in a polymerization process, the cocatalyst i) activates pre-catalyst particles, ii) participates in chain transfer reactions, iii) changes the isotacticity and molecular weight of the polymer [13], and iv) alters the kinetic stability and resistance to the decomposition of catalyst.…”

Organic Versus Inorganic Supports for Metallocenes: The Influence of Rigidity on the Homogeneity of the Polyolefin Microstructure and Properties

“…As a result of comonomer insertion in PE chains, SCB disturbs the polymer crystallization process . The thermal fractionation of copolymers by the SSA is based on the principle that the crystal lamellae thickness is correlated to the length of a successive methylene sequence, − based on the polyolefins microstructure, SCB, and SCBD. In particular, the number of SCB and SCBD along the polymer chains directly stimulates the formation of crystal units with different lamella lengths.…”

Recent Advances in Separation-Based Techniques for Synthetic Polymer Characterization

“…Specifically, the 2D contour maps generated from 2DLC revealed significantly broad distributions of branched molecules at any given molecular weight. Gas phase ethylene-butene copolymers produced with Ziegler–Natta style catalysts were studied by TREF × GPC cross fractionation to study the effect of alkyl-Al loading on polymer structure . Although the focus of the paper was catalysis, the TREF × GPC characterization data provided an excellent view of the bivariate distributions of CCD and MWD.…”

“…Gas phase ethylene-butene copolymers produced with Ziegler−Natta style catalysts were studied by TREF × GPC cross fractionation to study the effect of alkyl-Al loading on polymer structure. 131 Although the focus of the paper was catalysis, the TREF × GPC characterization data provided an excellent view of the bivariate distributions of CCD and MWD. The bivariate distributions of tacticity and molar mass in poly(1-octene) were evaluated by online comprehensive 2DLC (LAC × SEC) and offline analysis of SEC fractions by LAC.…”