DMCA
Block Index for Characterizing Olefin
BibTeX
@MISC{Copolymers_blockindex,
author = {Block Copolymers and Colin Li and Pi Shan and Lonnie G. Hazlitt},
title = {Block Index for Characterizing Olefin},
year = {}
}
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Abstract
Summary: Olefin block copolymers produced by chain shuttling catalysis exhibit crystallinity characteristics that are distinct from what would be expected for typical random olefin copolymers with comparable monomer compositions produced from either ‘single-site ’ or heterogeneous catalysis. Olefin block copolymers produced by chain shuttling catalysis have a statistical multiblock architecture. A unique structural feature of olefin-based block copolymers is that the intra-chain distribution of comonomer is segmented (statistically non-random). Fractionating an olefin block copolymer by preparative temperature rising elution fractionation, TREF, results in fractions that have much higher comonomer content than comparable fractions of a random copolymer collected at an equivalent TREF elution temperature. We have developed a ‘‘block index’ ’ methodology which quantifies the deviation from the expected monomer composition versus the analytical temperature rising elution fractionation, ATREF, elution temperature. When interpreted properly, this index indicates the degree to which the intra-chain comonomer distribution is segmented or blocked. The unique crystallization behavior of block copolymers determine the magnitude of the block index values because the highly crystalline segments along an otherwise non-crystalline chain tend to dominate the ATREF (and DSC) temperature distributions.
Keyphrases
block index characterizing olefin olefin block copolymer elution fractionation unique structural feature random copolymer block index methodology statistical multiblock architecture block index value typical random olefin copolymer non-crystalline chain preparative temperature equivalent tref elution temperature intra-chain comonomer distribution unique crystallization behavior comonomer content olefin-based block copolymer temperature distribution comparable fraction crystalline segment analytical temperature comparable monomer composition monomer composition intra-chain distribution block copolymer heterogeneous catalysis elution temperature catalysis exhibit crystallinity characteristic
