COMPARISON OF CORRELATION LENGTHS IN SEMIDILUTE POLYSTYRENE SOLUTIONS IN GOOD SOLVENTS BY QUASI-ELASTIC LIGHT-SCATTERING AND SMALL-ANGLE NEUTRON-SCATTERING

Quasi-elastic light scattering (QELS) and small-angle neutron scattering (SANS) experiments have been made on semidilute solutions of polystyrene (PS) in methylene chloride and tetrahydrofuran. The hydrodynamic screening length ( zeta //H) from QELS and the excluded volume screening length ( zeta ) from SANS are found to be proportional at concentrations well above the dilute-semidilute crossover. The power law C** minus **0**. **6**8 applies to the static quantity whereas this asymptotic exponent value is only found for zeta //H with PS fractions of molecular weight M greater than equivalent to 10**6. The dynamic length, zeta //H, is solvent independent while the static length is shown to be significantly shorter in methylene chloride, a result which is possibly related to differing extents of coil interpenetration in these solvents.