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Nonequilibrium morphology development in seeded emulsion polymerization. V. The effect of crosslinking agent
Author(s) -
Stubbs Jeffrey M.,
Sundberg Donald C.
Publication year - 2006
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.24063
Subject(s) - emulsion polymerization , monomer , polymer chemistry , penetration (warfare) , polymerization , morphology (biology) , radical , radical polymerization , emulsion , materials science , particle (ecology) , chemical engineering , chemistry , polymer , composite material , organic chemistry , oceanography , operations research , biology , engineering , genetics , geology
It is understood that a major controlling factor in the development of latex particle morphology is the extent to which second stage oligomeric radicals can diffuse into the particles after entry from the aqueous phase. This leads to the expectation that any factor which decreases the diffusion rate of second stage radicals should decrease radical penetration, and thus favor the formation of core–shell type morphologies. The occurrence of crosslinking reactions during the second stage may be one such factor, since the branched and crosslinked chains diffuse much more slowly (if at all) than their linear counterparts. This paper addresses the effect of the addition of crosslinking agent (a divinyl monomer) during the second stage polymerization on particle morphology. It is shown experimentally that, contrary to what one might expect, crosslinking during the second stage has very little, if any, effect on morphology. Modeling suggests that the reason is that the probability for radicals to develop a branch before penetrating a significant distance into the particles is very low (under conditions where full penetration is possible in the absence of crosslinking agent), especially for what is considered to be typical concentrations of crosslinking agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2043–2054, 2006