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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.

Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber.

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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.

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