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On the mechanism of formation of isotactic and syndiotactic polydiolefins
Author(s) -
Porri Lido,
Giarrusso Antonino,
Ricci Giovanni
Publication year - 2002
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200202)178:1<55::aid-masy55>3.0.co;2-h
Subject(s) - tacticity , monomer , polymer , polymer chemistry , materials science , catalysis , stereoselectivity , coordination polymerization , chemistry , polymerization , radical polymerization , organic chemistry , composite material
The mode of formation of isotactic and syndiotactic polymers from 1,3‐dienes is examined in the light of the most recent results. An interpretation is given for the formation of trans‐1,4 isotactic polymers from CH 2 =CH‐CH=CHR (R = Me, Et, Pr, etc.) type monomers with heterogeneous VCl 3 ‐based catalysts. Evidence is reported showing that stereoregular 1,2 or cis‐1,4 polymers derive from a growing polymer chain anti‐η 3 ‐bonded to the transition metal and a cis‐η 4 coordinated monomer. The influence on stereoselectivity of the substituents at the central carbon atoms of the monomer is discussed. The peculiar behavior of (Z)‐1,3‐pentadiene and 4‐methyl‐1,3‐pentadiene, which give 1,2 polymers with catalysts that give 1,4 polymers from other monomers, is attributable to the fact that they can coordinate trans‐η 2 , in addition to cis‐η 4 .