Correlation radii for polystyrene (PS) in poor and ⊖ 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) correlation radii, £ and |SANS, are reported for polystyrene (PS)/acetone-A6 (ACh) (DLS) and PS/ACd (DLS and SANS) solutions at near-critical concentration for (7.5 × 103 ≤ M_w/amu ≤ 25 × 103), (0 ≤ P/MPa < 120) and (12 ≤ t/°C < 91), during pressure and temperature quenches ending at or near precipitation. The data are well described in the (T,P)_yer projection using the multidimensional reduced scaling formalism introduced previously. The analysis yields scaling exponents (v ∼ VSANS = 0.65 ± 0.06) which are in agreement with the theoretical value, VTH = 0.63, but (f)° and £SANS are offset from each other, ((£)/|SANS) ∼ 3. The superscript "o" refers to correlation radii calculated from monomodal DLS correlograms using the StokesEinstein relation, (£)° = k_BT/(6πη_oD). D is the DLS diffusion coefïïcient, and η_o is the pure solvent viscosity. For PS/cyclohexane (CH) and PS/methylcyclohexane (MCH) solutions, (£°/esANs) ∼7 and ∼20, but for all three solvents, agreement improves when η_o is replaced with η, the solution viscosity. Then, (£/£SANS) ∼0.3, ∼0.2, and ∼3 for PS/AC, PS/CH, and PS/MCH, respectively. The results indicate the two probes are responding to the same or closely related clustering phenomena.