Measurement of the dependence of the averaged internal mode on the scattering vector and of the first internal mode on the concentration of polystyrene in solution using photon correlation spectroscopy

A study of the internal behavior of polystyrene in toluene and cyclohexane was done using photon correlation spectroscopy. In the experiments laser light of two different wavelengths was scattered from local concentration fluctuations in the polymer and autocorrelation function was calculated; The autocorrelation function can be written as a sum of decaying exponentials. The center-of-mass mode with a decay constant Dq{dollar}\sp2{dollar} is contained in every mode. D is the polymer diffusion coefficient and can be measured in low angle light scattering experiments and q is the magnitude of the scattering vector. Thus this center-of-mass mode can be factored out of the correlation function and a new function H(t) can be calculated. The experimental function was fit by a multiexponential fit routine to extract the value for the averaged internal mode; The quantity 2/{dollar}\tau\sb1{dollar} showed a concentration dependence in good solvent that has not been reported before. (Abstract shortened with permission of author.)