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.

The epoxy networks based on poly(propylene oxide) chains cross-linked by diglycidyl ether of Bisphenol A and reinforced by polyhedral oligomeric silsesquioxanes (POSS) provide a typical example of polymer nanocomposites with hierarchical architecture. In addition to characterizing the epoxy−POSS composites, this contribution demonstrates valuable applications of solid-state NMR spectroscopy. The size of domains in the nanocomposites was determined by high-speed MAS 1H−H spin-diffusion experiments, offering an alternative to the established methods like SAXS, EM, or AFM. While the latter might fail under certain circumstances (low contrast, or small domains), the 1H−1H spin-diffusion measurement yielded the size of unbroken primary domains, making also possible their distinction from “aggregates of primary domains”, the size of the latter being measured by EM or SAXS. Depending on the type of the investigated network the size of the POSS aggregates arising in the nanocomposites was determined to be ca. 1−20 nm. Investigations of molecular dynamics (various “domain-selective” relaxation and recoupling solid-state NMR experiments were applied) yielded information making possible the assignment of the contribution of molecular segments to thermomechanical properties like glass transition temperature and storage shear modulus, and to predict the products' ability to absorb mechanical energy. Remarkable motional heterogeneities were found not only in the amorphous phase, where mobile polymer segments of the “free” domains coexist with the immobilized chains of the “constrained” ones, but also in the crystallites of POSS building blocks, where the amplitudes of segmental reorientations occurring in the midkilohertz frequency region remain relatively large:  two-site 180° flips dominating to aromatic rings in the POSSPh crystallites are accompanied by the wobbling of the flip axes with an average fluctuation angle ca. 25°. Similarly, cyclopentyl substituents in the POSSCp crystallites undergo to ca. 35° rotational-diffusion motion.

Thermal, thermomechanical, tensile and gas transport properties of aliphatic polycarbonate-based polyurethanes (PC-PUs) and their nanocomposites with bentonite for organic systems were studied. Hard segments are formed from hexamethylene diisocyanate and butane-1,4-diol. All PC-PUs and their nanocomposites feature high degree of the phase separation. Three phase transitions were detected by temperature-modulated differential scanning calorimetry (TMDSC) and dynamic mechanical thermal analysis. TMDSC revealed the filler affinity both to soft and hard segments, even though the affinity to hard segments is much stronger. Elongation-at-break at ambient temperatures is mostly over 700%, which leads together with high tensile strength (in some cases) to very high toughness values (over 200 mJ/mm 3 ). The addition of 1 wt % of bentonite does not practically affect mechanical properties implying its very good incorporation into the PU matrix. Permeabilities and other gas transport properties depend on regularity of PC-diol and on hard segment content, but the variations are insignificant.

Polymer nanocomposites of epoxies with a novel filler, amino-functional butyltin oxide cage (stannoxane), were prepared and characterized. The nanofiller displays a promising antioxidizing effect, besides mechanical matrix reinforcement. The reinforcement can be assigned to physical interactions among the polymer bonded nanofiller. Moreover, the stannoxane cage undergoes a rearrangement to larger poly amino-functional nano-objects at higher temperatures, which highly reduces its extractability: it is practically not extractable from the nanocomposites in most cases. This, together with the fact that only a few weight percent are needed to achieve an optimal effect, makes it attractive as an antioxidative stabilizer. Epoxy–stannoxane nanocomposite synthesis, stannoxane reactivity and dispersion (morphology via TEM and SAXS), as well as the nanofiller effect on mechanical properties (DMTA) and on thermal stability are discussed. A brief comparison is drawn between the stannoxanes and the previously investigated POSS nanofiller.