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  • Thioketone-mediated polymerization with dithiobenzoates: proof for the existence of stable radical intermediates in RAFT polymerization.

Thioketone-mediated polymerization with dithiobenzoates: proof for the existence of stable radical intermediates in RAFT polymerization.

Macromolecular rapid communications (2012-05-05)
Thomas Junkers, Guillaume Delaittre, Robert Chapman, Fabian Günzler, Elena Chernikova, Christopher Barner-Kowollik
ABSTRACT

A novel dithioester control agent [dimethyltetrathioterephtalate (DMTTT)] is presented for the thioketone-mediated radical polymerization (TKMP) of n-butyl acrylate. The rate of polymerization is significantly decreased in the presence of DMTTT indicating formation of dormant radical species. During polymerization, molar masses increase linearly with monomer conversion with reasonably narrow initial molar mass distributions (PDI between 1.3 and 1.8), whereas the dispersity increases during the course of the polymerization due to irreversible termination of both propagating and dormant radicals. The present results thus highlight the possibility of a mixed mechanism operating in RAFT polymerization, which combines slow fragmentation (long-lived intermediates) and intermediate radical termination.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Butyl acrylate, SAJ first grade, ≥99.0%
Supelco
Butyl acrylate, analytical standard
Sigma-Aldrich
Butyl acrylate, ≥99%, contains 10-60 ppm monomethyl ether hydroquinone as inhibitor