Correlation radii for polystyrene (PS) in poor and Theta solvents from dynamic light and small angle neutron scattering. New data for PS/acetone. Remarks on PS/acetone, PS/cyclohexane, and PS/methylcyclohexane

Dynamic light scattering (DLS) and small-angle neutron scattering (SANS) co rrelation radii, xi and xi(SANS) are reported for polystyrene (PS)/acetone- h(6) (ACh) (DLS) and PS/ACd (DLS and SANS) solutions at near-critical conce ntration for (7.5 x 10(3) less than or equal to M-w/amu less than or equal to 25 x 10(3)), (0 less than or equal to P/MPa < 120) and (12 less than or equal to t/degrees C less than or equal to 91), during pressure and tempera ture quenches ending at or near precipitation. The data are well described in the (T,P)(psi cr) projection using the multidimensional reduced scaling formalism introduced previously. The analysis yields scaling exponents (nu similar to nu(SANS) = 0.65 +/- 0.06) which are in agreement with the theore tical value, nu(TH) = 0.63, but (xi)degrees and xi(SANS) are offset from ea ch other, ((xi)degrees/xi(SANS)) similar to 3 The superscript "o" refers to correlation radii calculated from monomodal DLS correlograms using the Sto kes-Einstein relation, (xi)degrees = k(B)T/(6 pi eta(o)D). D is the DLS dif fusion coefficient, and eta(o), is the pure solvent viscosity. For PS/cyclo hexane (CH) and PS/methylcyclohexane (MCH) solutions, (xi(o)/xi(SANS)) simi lar to 7 and similar to 20, but for all three solvents, agreement improves when eta(o) is replaced withy, the solution viscosity. Then, (xi/xi(SANS)) similar to 0.3, similar to 0.2, and similar to 3 for PS/AC, PS/CH, and PS/M CH, respectively. The results indicate the two probes are responding to the same or closely related clustering phenomena.