Synthesis and structural studies of an epoxidized natural rubber/titania (ENR-50/TiO2) hybrid under mild acid conditions

The ring-opening reaction of epoxide units in an epoxidized natural rubber/titania (ENR-50/TiO2) hybrid in the presence of acetic acid was studied using NMR techniques as well as FTIR spectroscopy. The thermal characteristics of the hybrid were evaluated using TG/DTG and DSC analyses. H-1 NMR results suggest that 86.51% of the epoxide rings had opened in the hybrid, and the C-13 NMR results revealed new peaks from the hybrid at 8 22.3, 34.8 and 72.2 ppm. 2D NMR (HMQC, HMBC and COSY) techniques further confirmed these assignments. FTIR spectra showed a characteristic Ti-O-C peak at 1028 cm(-1). The TG/DTG results showed four decomposition steps at 30-159, 229-325, 325-466 and 664-825 degrees C due to the presence of Ti moieties along with the mixture of polymer chains ie., the ring-opened and intact epoxides of ENR-50, which also led to an increase in the T-g value of the hybrid (27.8 degrees C) compared with purified ENR-50 (-17.7 degrees C).