Measurement of the first internal mode of polystyrene in cyclohexane and toluene through dynamic light scattering

A study of the longest internal relaxation time {dollar}\tau\sb1{dollar} of 8.42 {dollar}\times{dollar} 10{dollar}\sp6{dollar} M{dollar}\sb{\rm w}{dollar} macromolecular polystyrene dissolved in both toluene and cyclohexane was done through the use of photon correlation spectroscopy from scattered laser light. The data obtained (autocorrelation functions) were then analyzed by means of a multi-exponential fitting programme (Discrete) on the Cyber 830 computer and by a non-linear least squares program (NLLSQ) on an Apple IIe computer. The exponential decay constants derived from these fits were further used to obtain a value of {dollar}\tau\sb1{dollar} in each solvent and also to find the power relation between these decay constants and q, the magnitude of the scattering wave vector. The relaxation time {dollar}\tau\sb1{dollar}, together with the q dependence of the decay constant, was then compared to the predicted results from the Rouse-Zimm bead-and-spring model of polymers as well as other models and other researchers\u27 published results. (Abstract shortened with permission of author.)