Probing the effect of graphene surface chemistry on compatibility, crystallinity, and viscoelastic response of polylactic acid/polyvinylidene fluoride blends

Abstract

Polylactic acid (PLA)/polyvinylidene fluoride (PVDF)/graphene nanocomposites were prepared by solution casting technique to study the effect of graphene surface chemistry on blend compatibility. Surface and cross-sectional morphology and atomic force microscopy analyses revealed that the addition of hydrophobic graphene resulted in the highest level of compatibility in PLA/PVDF blends. The untreated graphene exhibited a more compatibilizing effect than the hydrophilic graphene. According to X-ray diffraction (XRD) results, the crystallinity of polymers was enhanced in the presence of graphene for the compatibilized blends through the interfacial assisted nucleation mechanism. The formation of β-phase PVDF crystals was also increased in the presence of PLA and graphene, especially for the blend loaded with hydrophobic functionalization. Based on XRD and rheological results, the order of graphene dispersion quality was as follows: hydrophobic> untreated>hydrophilic. The improved dispersion quality of graphene nanoplatelets, along with the higher interfacial modulus for the compatibilized blends, were found responsible for the observed enhancement in the elasticity of the samples. The current study demonstrated the promising potential of graphene nanoplatelets with hydrophobic functionalization in compatibilizing the immiscible PLA/PVDF blends. Moreover, the enhanced β-phase crystals of PVDF and increased PLA crystallinity are highly useful in advanced applications that require piezoelectricity and biocompatibility.