Free volume structure of PMMA based nanocomposites and its correlation with the thermal properties

Abstract

Free volume structure of amorphous polymers determines their bulk physical properties. In the case of polymer nanocomposites, free volume structure of polymer matrix is altered as a result of incorporation of nano-sized fillers in polymer matrix. In the present study, ortho-positronium (o-Ps) probe has been used to investigate the free volume structure of poly (methyl methacrylate), PMMA, in PMMA-SiC nanofibers composites. The nanocomposite films with SiC loading (0, 0.1, 0.2, 0.5, 1.0 and 2.0 wt.%) were prepared using solvent casting method. It is observed that on incorporation of SiC nanofibers, size of free volume holes in PMMA matrix increases whereas their number density decreases. The free volume size distribution is also alerted on incorporation of SiC nanofibers. The observed variations in free volume structure are explained invoking the interfacial layer around the nanofibers having a distinct free volume structure compared to bulk PMMA matrix. Thermal gravimetric analysis (TGA) measurements have been carried out to investigate the decomposition behavior of PMMA in the nanocomposites. The present study shows that in addition to nanofillers’ network, free volume structure of polymer phase in the nanocomposite plays significant role in thermal decomposition properties.Free volume structure of amorphous polymers determines their bulk physical properties. In the case of polymer nanocomposites, free volume structure of polymer matrix is altered as a result of incorporation of nano-sized fillers in polymer matrix. In the present study, ortho-positronium (o-Ps) probe has been used to investigate the free volume structure of poly (methyl methacrylate), PMMA, in PMMA-SiC nanofibers composites. The nanocomposite films with SiC loading (0, 0.1, 0.2, 0.5, 1.0 and 2.0 wt.%) were prepared using solvent casting method. It is observed that on incorporation of SiC nanofibers, size of free volume holes in PMMA matrix increases whereas their number density decreases. The free volume size distribution is also alerted on incorporation of SiC nanofibers. The observed variations in free volume structure are explained invoking the interfacial layer around the nanofibers having a distinct free volume structure compared to bulk PMMA matrix. Thermal gravimetric analysis (TGA) measurements have...