Discontinuity in the variation of intrinsic viscosity of polymers and their mixtures with temperature in dilute solutions

In recent years many workers have reported discontinuity (abrupt change) in the plots of intrinsic viscosity against temperature. Discontinuity has also been observed in the plot of intrinsic viscosity against the composition of solvent mixture. The difference in mobility of the side group of the polymer chain has been proposed as the probable cause of the discontinuity. The observed discontinuity has also been referred to as conformational transition. The changes in the conformations of polymer chains are also thought to be the reason for the observed discontinuity in the variation of the unperturbed dimension parameter and the refractive index increment with temperature. The viscometric resultsare presented, as a function of temperature obtained from poly(methyl methacrylate), poly(ethylene glycol) and their mixtures, polystyrene and poly(styrene-n-butyl methacrylate), under theta and non-theta conditions in dilute solutions. 14 ref.--AA