Investigation of equilibrium and non-equilibrium states of polymer blends by small-angle neutron scattering

Small-angle scattering of neutrons (SANS) has been applied to investigate the equilibrium properties of polymer blends, in particular the critical fluctuations in the homogeneous regions for d-PS/PS, PS/d-PB and d-PS/PVME. The transition between mean-field and Ising behaviours has been observed for PS/d-PB about 6 K above T_c. The non-equlibrium behaviour of the SANS structure factor of d-PS/PS has been studied after a temperature step has been applied. Only for very small scattering vectors does the time-dependent structure factor follow the predictions of the Cahn-Hilliard theory. Also, early stages of decomposition within the miscibility gap have been studied in this system and in d-PS/PVME. [PS = polystyrene; PB = polybutadiene; PVME = poly(vinyl methyl ether).]