Preparation and characterization of monodisperse polystyrene-silica nanocomposites

摘要

Polystyrene-silica nanocomposites were successfully prepared by UV-induced graft polymerization of styrene onto a silica surface. Composites were prepared by batch and continuous-circulation reactions, and results indicated that polystyrene was successfully grafted onto inorganic silica particles for both reactions. Scanning electron microscopy and thermogravimetry analyses of the composites indicated 45% volume increase and 37% polymer content after an optimal reaction time of 30 minutes, respectively, for the batch reaction. For the continuous-circulation reaction, the corresponding results were 63% volume increase and 42% polymer content after 140 min of reaction time. Fourier Transform-Raman spectroscopy analysis of composites showed the characteristic peaks of both silica and polystyrene thus confirming the successful graft-polymerization for both reactions. Disappearance of C-H and C=C ring stretching bands at 3070 and 1578 cm(-1) in composites after their optimal reaction times for both reactions indicated a possible ring opening mechanism due to prolonged exposal to the UV light source. For the batch reaction, composites showed new vibration bands at 1052 and 812 cm(-1) for asymmetric and symmetric Si-O-C stretching, respectively, indicating a covalent bond between the grafted polymer and silica surface. X-Ray photoelectron spectroscopy (XPS) analysis showed an increase in the elemental concentration of carbon from 5 to 46% for 30 minute composites in batch reaction. XPS analysis also indicated that the relative OH group content of the surface of the silica particles determines the effectiveness of the graft-polymerization of styrene.