We present here part of an ongoing study on structure-processing-property relationships in cubic silsesquioxane (cube) nanocomposites. Here, we focus on imide nanocomposites prepared from octaaminophenylsilsesquioxane (OAPS) as a model nanobuilding block for rigid, high-temperature hybrid nanocomposite materials. OAPS units are linked NH 2 vertex to NH 2 vertex by reaction with various dianhydrides to form three-dimensional nanocomposites. The architecture of the organic tethers between vertices can be manipulated to optimize processability, rigidity, and thermomechanical properties. Studies were initiated using an extreme tether structure with zero flexibility prepared by solvent casting and then curing mixtures of OAPS with pyromellitic dianhydride (PMDA) at 330 °C. The resulting materials are extremely brittle, making thermomechanical property measurements quite difficult. Tether rigidity, length, and cross-link densities were then modified using reactions of OAPS with oxydiphthalic anhydride (ODPA) and diluting with oxydianiline (ODA) to adjust nanocomposite stiffness. FTIR and DMA of the OAPS/ODPA/ODA nanocomposites suggest that cure temperatures of >500 °C are necessary for optimal imidization. However, increasing the cross-link density alone by increasing OAPS loading without curing at high temperatures also significantly improves thermomechanical stabilities. DMA, TGA, and nanoindentation measurements show that macroscopic relaxation is eliminated completely at OAPS loadings of >60 mol % providing 5% mass loss at temperatures >570 °C and compressive moduli of ≈3.8 GPa.

Selected epoxy-functionalized cube nanocomposites were prepared from octa(aminophenyl)silsesquioxane (OAPS), poly(aminophenyl)silsesquioxane (PAPS), octa(dimethylsiloxypropylglycidyl ether) silsesquioxane (OG), diglycidyl ether of bisphenol A (DGEBA) and diaminodiphenylmethane (DDM). A systematic comparison of properties was conducted using GPC, FTIR, 29Si NMR, TGA, and DMA. In these studies, we find that (1) tethers with aromatic components increase char yields and decomposition temperatures, (2) cube loadings are important in thermal stabilities, (3) aromatic tether structure, short lengths and high cross-link densities reduce tether segmental relaxation motions which in turn stiffen the network and minimize macroscopic glass transitions. Finally, nanocomposites prepared from OAPS and PAPS exhibit nearly identical thermomechanical properties with PAPS offering a low cost alternative to OAPS.

Highly swellable poly(ethylene oxide) (PEO) gels were prepared by anionic ring‐opening polymerization of diepoxy end‐capped PEO (3400 g mol−1) and PEO (8000 g mol−1) using dianionic glycerol and glycolic acid initiators at scales of up to 50 g diepoxide. The glycerol‐derived materials swell to almost 20 times their mass in water. The driving force for rapid swelling appears to arise during ‘crystallization’, as segments between crosslinks are forced to pack under conditions that create high‐energy domains within the material. Solvation and therefore swelling are driven by the release of the resulting packing energy. These observations may offer insight into methods for designing other highly swellable materials. When the polyfunctional initiators have groups with different reactivities (e.g. alkoxide versus carboxylate), as might be expected, the more nucleophilic functional group appears to dominate the ring‐opening polymerization process. Copyright © 2007 Society of Chemical Industry