Hyperbranched polyurethane-urea-imide/o-clay-silica hybrids: Synthesis and characterization

Hyperbranched polyurethane-urea-imide/o-clay-silica (HBPUI/o-clay-silica) hybrid coatings were prepared using organically modified clay (o-clay) in the presence of cetyltrimethylammonium bromide (CTAB) and tributylhexadecylphosphonium bromide (TBHPB) cationic surfactants and were further surface-grafted by 3-aminopropyltrimethoxy silane (APTMS). Hybrid polyesters were prepared by incorporating into the first generation hyperbranched polyester polyol (HBP-G1) at various concentrations. The NCO-terminated hybrid prepolymers and chain extensions were achieved by imide chain extender. The modified clays were characterized by powder X-ray diffraction and Fourier transform spectroscopy. Viscoelastic, thermomechanical, and surface topology studies were performed by dynamic mechanical thermal analysis (DMTA), thermogravimetric analyser (TGA), universal testing machine (UTM), atomic force microscopic (AFM), and contact angle measurements. TGA and DMTA indicated higher thermal stability and glass transition temperature (Tg) of TBHPB-modified hybrid coatings compared with the CTAB counterparts, which increased with increasing silane-modified o-clay content. Water contact angle suggested increasing hydrophobicity of higher silane-modified o-clay containing coatings, while AFM confirmed the dispersibility of silane-modified o-clay into polymer matrix; the extent of dispersion increased with increasing silane-modified o-clay content in the hybrid formulation. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012