Microwave assisted synthesis and spectroscopic characterisation of diphenyl carbonate functionalised nanoporous starch

The functionalisation of potato starch using a greener and biologically important molecule, i.e., diphenyl carbonate under microwave irradiation to obtain nanoporous diphenyl carbonate/starch composites is demonstrated. A series of spectroscopic techniques were used to investigate the bonding between diphenyl carbonate and starch, along with morphology and nature of modified starch. The regular surface of pristine starch was noticeably modified to a porous structure as evidenced by FESEM and TEM. Both H-1 and C-13 NMR studies revealed that the features of diphenyl carbonate were retained in modified starch. The line widths of C-13 NMR signals were enhanced by 190-360 Hz referring to the crystalline nature of the modified form. FT IR studies showed bands at 1641 and 1774 cm(-1) which confirms the linkage of diphenyl carbonate with starch. FT IR studies supported a substantial removal of hydrogen bonding from the native starch surface after phenylation, referring to hydrophobic nature of modified starch. The shift of band position from 867 to 854 cm (- 1) in Raman studies is attributed to the C-C-H or C-O-C bending linkage of carbon to diphenyl carbonate. The X-ray diffraction and thermogravimetric studies further supported the rigid and porous structure of modified starch. These modified starch possessing open structures is envisaged to act as a host materials for adsorption of hydropbobic molecules.