Effect of an organoclay on the reaction‐induced phase‐separation kinetics and morphology of a poly(ether imide)/epoxy mixture

Organically modified layered silicates with a hydroxyl‐substituted quaternary ammonium surfactant as the modifier were incorporated into a mixture of poly (ether imide) and epoxy with 4,4′‐diaminodiphenyl sulfone as the hardener. The influence of the organically modified layered silicates on the reaction‐induced phase‐separation kinetics and morphology of the poly(ether imide)/epoxy mixture was investigated with time‐resolved small‐angle light scattering, phase‐contrast microscopy, and scanning electron microscopy. The phase‐separation kinetics were analyzed by means of the temporal evolution of scattering vector q _m and scattering intensity I_m at the scattering peak. The organically modified layered silicates obviously facilitated an earlier onset of phase separation but reduce the phase‐separation rate and greatly retarded the domain‐coarsening process in the late stage of spinodal decomposition. The temporal evolution of both q _m and I_m followed the power law q _m ～ (t ? t_os)^?α and I_m ～(t ? t_os)^?β, where t is the reaction time, t_os is the onset time of phase separation, and α and β are growth exponents. For the samples filled with organically modified layered silicates, α crossed over from 0 to about 1/3, following Binder–Stauffer cluster dynamics, and an interconnected phase structure was observed for cure temperatures ranging from 120 to 230°C. For the unfilled samples, the interconnected phase structure was observed only at cure temperatures below 140°C. At temperatures above 150°C, α crossed over from 0 to 1/3 < α ≤ 1 under the interfacial tension effect, following Siggia's theory, and the domain‐coarsening rate was very fast; this resulted in macroscopic epoxy‐rich domains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1205–1214, 2007