Static inhomogeneities and dynamic fluctuations of temperature sensitive polymer gels

The static inhomogeneities and dynamic tluctuations in polymer gels have been studied by light scattering as a function of the gel preparation temperature, T-prep, and the cross-link density. The light scattered intensity of polymer gels was decomposed to two parts; the intensities due to the thermal fluctuations, I-F, and the frozen inhomogeneities, I-C. The analysis employing ensemble ([..](E)) and time averaging ([..](T)) of light scattered intensity disclosed that [I-F](T) (the thermal fluctuations) depends neither on the cross-link density nor the temperature of gel preparation, but on the temperature of observation. On the other hand, [I-C](E) (the frozen inhomogeneities) is a function of both temperatures at preparation and at observation. This clearly shows that gel is matter with dynamic fluctuations superimposed on the static frozen inhomogeneities. The latter are built-in inhomogeneities due to topological constraints of the gel by cross-linking formation. (C) 1998 Elsevier Science B.V. All rights reserved.