Dynamic and static light scattering study of the formation of cross-linked PMMA gels |
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Authors: | V Lesturgeon T Nicolai D Durand |
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Institution: | (1) Chimie et Physique des Matériaux Polymères (UMR CNRS), Université du Maine, 72085 Le Mans Cedex 9, France, FR |
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Abstract: | Free radical co-polymerization of methyl methacrylate (MMA) and ethyl glycol dimethyl metacrylate (EGDMA) was investigated
in solution at different molar ratios R = EGDMA]/MMA] between 0 and 0.05. Initially mainly linear PMMA was formed with weight average molar mass 7.5 g/mol independent of R. At larger reaction extents branched polymers were formed and the systems gelled. The scattering intensity rose initially
with the reaction extent, but reached a plateau value at larger reaction extents. The plateau value increased strongly with
R. Dynamic light scattering showed the appearance of a slow relaxation not observed in linear PMMA solutions. The data can
be interpreted by assuming that the excess scattering originates from the branching points and relaxes through self diffusion
of the branched particles. The results agree with predictions of the percolation model for gelation and Rouse dynamics. Viscosity
measurements corroborate this interpretation. Measurements on a progressively diluted sample quenched close to the gel point
again showed quantitative agreement with the percolation model for gelation.
Received 11 May 1998 and Received in final form 22 October 1998 |
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Keywords: | PACS 36 20 -r Macromolecules and polymer molecules - 61 10 -i X-ray diffraction and scattering - 82 70 Gg Gels and sols |
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