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Activated esters in the cationic polymerization of styrenes
Author(s) -
Matyjaszewski Krzysztof
Publication year - 1988
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19880130131
Subject(s) - cationic polymerization , chemistry , polymerization , polymer chemistry , triflic acid , covalent bond , lewis acids and bases , styrene , ionic polymerization , perchloric acid , reversible addition−fragmentation chain transfer polymerization , alkylation , living cationic polymerization , racemization , chain transfer , macromolecule , polymer , organic chemistry , ring opening polymerization , copolymer , catalysis , radical polymerization , biochemistry
Abstract Cationic polymerization of styrenes initiated by protonic acids can proceed via covalent intermediates. Calculations of the charge distribution in these species show low probability of transfer reactions. Macromolecular and model covalent species in the perchloric acid initiated polymerization of styrene have been directly observed by NMR. Esters formed with triflic acid are very reactive and participate in Friedel‐Crafts alkylation at −78 °C. Acetates become active only in the presence of protonic and Lewis acids. 1‐Phenylethyl trifluoroacetate activated with the parent acid reacts with styrene faster than the acid does. The racemization of the optically active ester is faster than its incorporation indicating an ionic mechanism of propagation in this system. Activation by Lewis acids proceeds by the reversible formation of complexes. Some systems yield polymers with low polydispersity.