Epoxy−amine networks were modified with well-defined inorganic building blockspolyhedral oligomeric silsesquioxanes (POSS). POSS molecules were incorporated in the organic−inorganic networks as dangling units of a network chain or as network junctions. Mono- or polyepoxide POSS monomers were used to prepare the two types of networks. The structure of the POSS-containing networks, including the structure evolution during network formation, was determined by SAXS, WAXS, and TEM. The POSS pendant on a network chain shows a strong tendency toward aggregation and crystallization, depending on the POSS organic ligands. During network formation, ordering of the crystal domains takes place. The POSS−POSS interaction is the main factor controlling the network structure. Also, the polyepoxy POSSs monomers aggregate in the organic matrix; however, during network formation the system becomes more homogeneous and POSSs as network cross-links become better dispersed. Still, in the cured organic−inorganic networks the POSS junctions are slightly aggregated, and the extent of aggregation increases with decreasing POSS cross-link functionality.

The rubbery epoxy network, based on diglycidyl ether of Bisphenol A (DGEBA) and poly-(oxypropylene)diamine (Jeffamine D2000), was reinforced with a nanometer-sized inorganic building blocksspolyhedral oligomeric silsesquioxanes (POSS). The organic-inorganic networks contained POSS as pendant units of a network chain or as network cross-links of various functionality. Thermomechanical properties and thermal stability of the POSS-containing networks were determined by DMA and TGA. The strongest reinforcement was achieved in the networks with pendant POSS forming ordered crystalline domains, which act as physical cross-links. The POSS skeleton with "soft" flexible substituents, such as octyl, shows formation of weak aggregates only, which do not contribute to reinforcement. The rubbery modulus of the networks with POSS in a junction grows with increasing POSS functionality due to enhanced network cross-link density. These networks are more homogeneous, and the modulus of the network with the octafunctional POSS junction well agrees with theoretical prediction. The mechanical properties are affected mainly by POSS-POSS interactions while the POSS-network chain interactions are of minor importance.

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The high degree of self-assembling of epoxide-based products made from functionalized organosilica building blocks, functionalized oligo(oxypropylene)-diamine and/or -triamine, and colloidal silica nanoparticles was evidenced by solid-state NMR spectroscopy, small-angle X-ray scattering (SAXS), and atomic force microscopy (AFM). Under optimized conditions of preparation, isolated siloxane cagelike clusters arise in the reaction mixture. No cleavage of oxirane rings occurs before thermal curing, and thus the whole process is well controlled. The presence of silica nanoparticles accelerates the kinetics of polycondensation and affects the condensation rate of siloxane units in final products. Two-dimensional solid-state NMR experiments (2D CRAMPS, 2D 1H−13C and 1H−29Si HETCOR, WISE) revealed differences in structure and segmental dynamics of final films as well as in self-organization and homogeneity degree depending on reaction conditions. Ideally, siloxane cagelike clusters are regularly dispersed within the bulk and oxypropylene chains form phase which separates organic tails of siloxane clusters. The SAXS determined distance between clusters (1.8 nm) well corresponds to the constraints determined by NMR spin-diffusion experiments. Polymer interaction with silica nanoparticles is confirmed by two-dimensional 1H−29Si HETCOR experiments.