Internal motions of linear chains and spherical microgels in dilute solution

It is well known that for a flexible polymer chain in dilute solution, two different types of motions mainly contribute: the translation motion of the centres of mass of individual polymer chains; and the internal modes generated from the motions of segments with respect to the centre of mass of the chain. During the past two decades, with the advances in light scattering instrumentation and sophisticated methods of data analysis, both types of motions can be distinguished in experiments and utilized for testing molecular theories of polymer chain dynamics in dilute solution. In this article, we first review some previous experiments, in particular the dynamical properties of polystyrene (PS) and polyisoprene (PIP) chains in good and theta (Q) solvents, and then our own results, including a comparative study of the internal motions of poly(N-isopropylacryl-amide) (PNIPAM) linear chains and spherical microgels under good solvent conditions. The final part of this article deals with how the solvent quality (the solution temperature) affects the internal mobility of PNIPAM linear chains and microgels.