Numéro |
J. Phys. II France
Volume 3, Numéro 3, March 1993
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Page(s) | 407 - 419 | |
DOI | https://doi.org/10.1051/jp2:1993140 |
J. Phys. II France 3 (1993) 407-419
Polymerization in non-uniform reaction fields : Monte Carlo description of structure buildup during photopolymerization
Anshu M. GuptaDepartment of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, U.S.A.
(Received 9 July 1992, accepted in final form 10 November 1992)
Abstract
A Monte Carlo 3D off lattice percolation in a non-uniform reaction field is reported. Monomers are simulated as point particles
of functionality (coordination number),
f=3. The non-uniform field is expressed as an exponentially decaying reaction probability in one dimension tailored to simulate
the photopolymerization process. It is argued that tubular reactors and other polymerizations in non-uniform fields will show
similar qualitative features. Two cases of molecular mobility are studied. In the first limit molecules can only react in
immediate neighborhoods corresponding to diffusion limited growth. In the second any two units can react. Results based on
the distinction of whether one or both units must be activated before reaction are reported. It is found that for the particular
type of non-uniform field considered reaction gradients results in inhomogeneous gelation at low conversions. Reaction gradients
cause large spatial heterogeneities in the size distribution of the molecules and also introduce large polydispersities. These
results are compared with recent experimental observations on photopolymerizations and tubular reactors.
82.35 - 61.41 - 61.20J
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