The physical properties of sulfonated graphene/poly(vinyl alcohol) composites

Composites of poly(vinyl alcohol) (PVA) with sulfonated graphene (SG) show fibrillar, dendritic and rod like structures for SG1, SG3 and SG5 samples, respectively, where the number indicates weight percent of SG. Differential scanning calorimetry shows a new peak in addition to that of PVA arising from the supramolecular organization of the components in SG1 and SG3. Seventeen percent and 36% increases of PVA crystalline thickness and 77% and 79% increases in amorphous overlayer thickness for SG1 and SG3 over PVA are evident from small angle X-ray scattering results but SG5 does not show any change. Atomic force microscopy results of SG suggest aggregation at higher concentration and the composites exhibit composition dependent mechanical properties with the highest increase of stress (177%), strain at break (45%) and toughness (657%) in SG3 over PVA. Young's modulus increases with increasing SG concentration with a maximum 180% increase in the SG5 sample. The storage modulus of SG3 shows the highest increase (1005%) over PVA. A 10 orders of magnitude increase of dc conductivity over PVA and a 10-fold increase in the dendritic SG3 to that of other composites are observed. SG1 is semiconducting, SG3 shows an electronic memory and SG5 exhibits a rectification property. (C) 2011 Elsevier Ltd. All rights reserved.