Optical Probe Study of Solutionlike and Meltlike Solutions of High Molecular Weight Hydroxypropylcellulose
Scattering from Polymers: ACS Symposium Series
Quasi-elastic light scattering spectroscopy spectra of optical probes diffusing in hydroxypropylcellulose (HPC):water (1,2) are well-described as a sum of two modes, here described as 'fast' and 'slow'. There are correlations between the experimental parameters that characterize spectra and system properties including probe radius and polymer concentration; these correlations separate probe behavior into distinct small-probe and large-probe regimes. For the two probe-size regimes, the fast and slow modes can be grouped into three physical regimes, namely a long time scale regime for the large-probe slow mode, an intermediate time scale regime for the small-probe slow mode and the large-probe fast mode, and a broad time scale regime for the small-probe fast mode. Physical interpretations for the three physical regimes are proposed. The probe diameter separating small-probe and large-probe behavior is the same at all polymer concentrations, consistent with hydrodynamic models for polymer dynamics, but inconsistent with models that assume the existence of a transient gel pseudolattice in solution. It has previously been reported that the zero-shear viscosity of HPC solutions shows a sharp change, at transition concentration c+, in the functional form of its concentration dependence, from a stretched exponential at lower concentration to a power law at higher concentrations. We observe a sharp transition in the concentration dependence of mode parameters at the same concentration c+, supporting the interpretation that the transition is physically real, and not an artifact of the fitting process.
Streletzky, Kiril A. and Phillies, George D.J., "Optical Probe Study of Solutionlike and Meltlike Solutions of High Molecular Weight Hydroxypropylcellulose" (1999). Physics Faculty Publications. 336.