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Gel growth in free radical crosslinking copolymerization: Effect of inactive gel radicals
Author(s) -
Okay Oguz
Publication year - 2000
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/1521-3919(20000701)9:6<354::aid-mats354>3.0.co;2-9
Subject(s) - radical , copolymer , polymer chemistry , chemistry , photochemistry , organic chemistry , polymer
A kinetic model is presented for the post‐gelation period of free‐radical crosslinking copolymerization. The model takes into account the trapped radical centers in the gel forming system. It was shown that the weight fraction of sol, W s , relates to the number of crosslinked units per weight‐average primary molecule, ε , through the equation $ W_s={(n-{ε})^{n-1}\over {ε}(n+{ε})^{n-2}}$ where n = 2 for Flory's most probable molecular weight distribution, and n = 3 for primary molecules formed by radical combination. Calculation results demonstrate that the existence of trapped radicals significantly affects the growth rate of the gel molecule. It increases the total radical concentration and accelerates the gel growth. The difference in the predictions with and without considering the trapped radicals becomes significant as the crosslinker concentration decreases or, as the vinyl group reactivity on the crosslinker or on the polymer decreases.