Light‐scattering studies of crosslinking unsaturated polyesters with methyl acrylate

The Debye‐Bueche theory of light scattering of inhomogeneous solids was applied to a three‐dimensional crosslinking process. A series of unsaturated polyesters of an average degree of polymerization of 7.4 were prepared in which the double bond spacings were varied. These polyesters were crosslinked with methyl acrylate in 1 : 2, 1 : 3, and 1 : 4 polyester double bond: monomer ratios. The crosslinking process was followed up with measurements of the light‐scattering envelope beyond the gel point. Parameters corresponding to the extent of inhomogeneities and the mean square deviation of the local refractive index from the average were evaluated. The data were interpreted by proposing a gelation mechanism which can be separated into three phases by optical means.