Melt rheology and thermomechanical behavior of poly(methyl methacrylate)/reduced graphene oxide nanocomposites

Abstract

Thermomechanical and rheological behavior of poly(methyl methacrylate) (PMMA)/reduced graphene oxide (RGO) nanocomposites prepared via in situ polymerization using sheet casting method was investigated. Scanning electron microscope and transmission electron microscope were used to study the microstructure of nanocomposites in terms of dispersion of RGO and polymer–RGO interaction. The thermomechanical properties were investigated using dynamic mechanical analyzer, and it was found that the incorporation of RGO sheets into PMMA matrix resulted in an increase in both storage modulus and glass transition temperature (Tg) as compared with neat PMMA. Storage modulus showed an increase of 40% and 46% at a loading of 0.5 and 1.0 wt% RGO, respectively. The glass transition temperature showed an increase of 20°C (104°C for neat PMMA) at RGO loading of 2.0 wt% (124°C for sample PMMA‐2.0). The complex viscosity and moduli (storage and loss) as a function of angular frequency also showed an increase with increasing amount of RGO. A significant increase in melt viscosity of PMMA observed in case of sample having 0.5 wt% RGO (sample PMMA‐0.5) could be due to the formation of interconnected network of RGO in PMMA matrix and can be considered as rheological percolation threshold. A drop in the crossover frequency was registered with increase of RGO loading that does not directly correlate with the percolation threshold concentration, representing an increase in solid‐like behavior. Secondly, the complex viscosity did not change with RGO loading at higher frequency, which showed that the short‐range PMMA relaxations were unaffected by RGO. Copyright © 2015 John Wiley & Sons, Ltd.