Catalytic and reinforcing effects of polyhedral oligomeric silsesquioxane (POSS)-imidazolium modified clay in an anhydride-cured epoxy

In this article, we report novel epoxy-based hybrids prepared via incorporating 1,2-dimethyl-3-(benzyl-heptaisobutyl-POSS) imidazolium chloride (POSS-IMC) and POSS-IMC-modified clay (POSS-MMT) into the resin based on 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate (ECHM) and hexahydrophthalic anhydride (HHPA). We demonstrate that both POSS-IMC and POSS-MMT can reduce the cure temperature of the epoxy/anhydride system, and the catalyzing effect involves chemical reactions between POSS-IMC and ECHM/HHPA, which may lead to the attachment of POSS cages at chain ends. The incorporation of the POSS-IMC, free and ionically bonded in clay, gives rise to dissimilar morphologies that affect the thermo–mechanical properties of the hybrids. The ECHM/HHPA/POSS-IMC resin exhibits a slight improvement in glassy modulus as compared with the neat ECHM/HHPA resin, which is attributed to the formation of sub-micron and nano-sized POSS domains that act as physical cross-link points hindering polymer chain motions. The much enhanced reinforcing effect of POSS-MMT is ascribed to the effective stress transfer between the matrix and clay layers that may originate from the strong interactions between the pendent POSS in the network and POSS attached to the clay surfaces. Reduction in coefficient of thermal expansion (CTE) was also found for the hybrids.