Facile one pot synthesis of graphene oxide (GO) by sonication assisted mechanochemical approach has been reported here. The amalgamation of ultrasonication and mechanical stirring has assisted the synthesis of GO in a short time duration of only 4 hours with good reaction yield. The structural characterization of GO was performed by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Visible spectroscopy and Raman spectroscopy. Atomic force microscopic (AFM) analysis manifested the flake like morphology of GO with average sheet thickness ~1.5 nm. AFM also provides important information about the surface roughness. Transmission electron microscope (TEM) analysis gave clear visualization of well exfoliated structure of GO in the form of thin flakes. The field emission scanning electron microscope (FESEM) analysis revealed a crimpling surface morphology of GO. The average size of GO flake as revealed through various morphological as well as light scattering techniques was around 3 μm. Moreover, important surface chemistry of the synthesized GO was well ascertained through contact angle analysis, AFM analysis and zeta potential analysis.

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Curing of polyurethane prepolymer with three hyperbranched polyol was studied using FTIR spectroscopy. The disappearance of the strong isocyanate absorption peak was followed with time and temperature to determine the reaction kinetics. It was shown that all the hyperbranched polyols followed the second order kinetic equation and the reaction rate enhanced with increase in the number of the functional groups of the hyperbranched polyol. Activation energy, activation enthalpy, and activation entropy were also measured. The swelling character of the polyurethanes was investigated with the help of gel fraction, degree of crosslinking, and average molecular weight between crosslinks. Atomic force microscopy indicated phase separated morphology of the cured polyurethanes. The thermal, mechanical, and thermomechanical properties were enhanced when the number of the functional groups in the hyperbranched polyols was increased. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 731–745, 2009

This review describes the synthesis of oxygen heterocycles by palladium-mediated cyclization published during 2003 to 2007.