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Rate-controlling events for radical exit in electrosterically stabilized emulsion polymerization systems

Citation

Thickett, SC and Gilbert, RG, Rate-controlling events for radical exit in electrosterically stabilized emulsion polymerization systems, Macromolecules, 39, (6) pp. 2081-2091. ISSN 0024-9297 (2006) [Refereed Article]

Copyright Statement

Copyright 2006 American Chemical Society

DOI: doi:10.1021/ma052224d

Abstract

The mechanism controlling radical loss by exit (desorption) in electrosterically stabilized emulsion polymerization particles was obtained from kinetic studies. Using RAFT-controlled radical polymerization techniques, polystyrene particles stabilized with differing lengths of poly(acrylic acid) chains bound to the surface were synthesized, with the hydrophilic block of low polydispersity, and of various degrees of polymerization. After removal of the RAFT agent, these latexes were used in seeded emulsion polymerization experiments with styrene, with the radical loss kinetics studied through the use of γ-radiolysis dilatometry. The size of the particles is such that they follow "zero−one" kinetics, so the sole rate-determining step for radical loss is by exit. The rate coefficient for exit (k) of these latexes was obtained directly from the non-steady-state relaxation period. A significant decrease in k occurs (by a factor of 10) relative to ionically stabilized latexes of corresponding size, even for particles with very small hydrophilic layers. The value of k was smaller for latexes with greater length of the hydrophilic block, consistent with the hypothesis that exit in electrosterically stabilized systems is bound by a restricted diffusion through the hydrophilic polymeric layer on the surface. Modification of the Smoluchowski treatment for diffusion-controlled rate coefficients to allow for diffusion through two different regions provides an expression for the rate coefficient of radical desorption out of a particle in these systems; semiquantitative agreement with experiment was obtained.

Item Details

Item Type:Refereed Article
Research Division:Chemical Sciences
Research Group:Macromolecular and Materials Chemistry
Research Field:Polymerisation Mechanisms
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
Author:Thickett, SC (Dr Stuart Thickett)
ID Code:99413
Year Published:2006
Web of Science® Times Cited:27
Deposited By:Chemistry
Deposited On:2015-03-23
Last Modified:2015-04-27
Downloads:0

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