Swelling-induced modulation of static and dynamic fluctuations in polyacrylamide gels observed by scanning microscopic light scattering

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Abstract
The nature of inhomogeneities in vinylpolymer gels has hardly been clarified yet. Inhomogeneities on submicron and nanometer scales in polyacrylamide gels have been investigated by using a scanning microscopic light-scattering system and applying a general formula for an ensemble-averaged correlation function. The network structure of the gels is modified by varying the preparation conditions and can be roughly divided into two types. Swelling-induced modulation of inhomogeneities depends on the type of the network structure. At low monomer concentrations in preparation, both submicron- and nanometer-scale inhomogeneities increase with swelling. At high monomer concentrations in preparation, submicron-scale inhomogeneities increase with swelling, but nanometer-scale inhomogeneities decrease anomalously. This behavior is explained by a model of inhomogeneous network structure of vinylpolymer gels, where macrogel is formed from a large number of microgel particles.