Static inhomogeneities and dynamics of swollen and reactor-batch polymer gels

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Abstract
The dynamic light scattering study has been carried out on swollen and reactor-batch gels of poly(N-isopropylacrylamide) (NIPA) in water as a function of polymer volume fraction, φ. The scattered intensity from these gels showed strong intensity fluctuations dependent on the sample position. The ensemble (i.e., position) average scattered intensity, 〈I〉 E , increased by swelling for all gels prepared at different initial monomer concentrations, indicating an increase of the static inhomogeneities by swelling. On the other hand, the dynamic component, e.g., the intensity component of the thermal fluctuations, I F , decreased by swelling. The collective diffusion coefficient, D, increased with increasing φ and by swelling. The physical meaning of the static inhomogeneities and the dynamics of gels are discussed. Furthermore, the concentration dependence of the diffusion coefficient is discussed as a function of φ.