Effects of a chemically reacting, 2 nm size heterogeneity on polymerization: A dielectric relaxation study

We report a real-time dielectric study of polymerization of a diepoxide–triamine mixture containing varying amounts of a chemically reacting, 2 nm size structural heterogeneity of a silica based molecule, polyhedral oligomeric silsesquioxane (POSS), bearing ∼11 epoxide groups. As the amount of substituent POSS in the polymerizing liquid was increased, the dc conductivity, the time for gelation, the static permittivity and the time to reach a certain relaxation time increased, and the dielectric relaxation spectra broadened. The rate of increase in the relaxation time during isothermal polymerization varied with the amount of the substituent POSS. Continuous change in the covalent bonded structure on polymerization with POSS alone showed pronounced features caused by an increase in the interfacial or electrode polarization. The added nano-heterogeneity of POSS that becomes ultimately a part of the polymer's network structure had qualitatively the same effect on the relaxation features during polymerization as the postulated dynamic heterogeneity on cooling a pure liquid.

► Nanometer size heterogeneity increases the gelation time and the relaxation time.
► The dielectric relaxation spectra is broadened as by dynamic heterogeneity.
► Polymerization kinetics differs from that measured by calorimetry.