Synthesis and structural studies of an epoxidized natural rubber/titania (ENR-50/TiO<inf>2</inf>) 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. 1H NMR results suggest that 86.51% of the epoxide rings had opened in the hybrid, and the 13C NMR results revealed new peaks from the hybrid at δ 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 °C due to the presence of Ti moieties along with the mixture of polymer chains i.e., the ring-opened and intact epoxides of ENR-50, which also led to an increase in the Tg value of the hybrid (27.8 °C) compared with purified ENR-50 (-17.7 °C).