Effects of the molecular level dispersion of graphene oxide on the free volume characteristics of poly(vinyl alcohol) and its impact on the thermal and mechanical properties of their nanocomposites

Abstract

Poly(vinyl alcohol), PVA, reinforced with carbon nanofillers has shown drastic variations in thermal as well as mechanical properties. In order to establish structure-property correlations, these variations have been correlated with modifications in the hydrogen bonding structure as well as the crystallinity of the PVA matrix without paying much attention to molecular packing in the amorphous region of this semicrystalline polymer. In order to investigate the molecular packing in PVA-graphene oxide (GO) nanocomposites, free volume characterization of PVA-GO nanocomposites has been carried out using ortho-positronium (o-Ps) probe. The variations in free volume size, density and size distribution have been determined through o-Ps lifetime and the corresponding intensity as well as its lifetime distribution. The variation in hydrogen bonding and its effect on crystallinity has been determined by Fourier Transform Infra Red (FTIR) and X-ray diffraction (XRD) measurements. The variation in the thermal (glass transition temperature) and mechanical (Young's modulus, tensile strength and percentage strain at break) properties of the nanocomposites is explained in view of the free volume structure and crystallinity of the PVA matrix which are severely modified due to the molecular-level dispersion of GO sheets in the PVA matrix.

Suppressing Salt Transport through Composite Pervaporation Membranes for Brine Desalination

“…%). This observation confirmed the formation of hydrogen bonding between hydroxyl/carboxylate groups on GO and hydroxyl groups on PVA chains, which was consistent with those of other studies [14,45,46].…”

“…After incorporating the GO into PVA matrix, no clear GO peak can be observed. This observation was in good agreement with the previous researches [14,45]. This can be attributed to the good interfacial compatibility between GO and PVA: the presence of carboxyl groups and hydroxyl groups on GO can form hydrogen bonding with hydroxyl groups on PVA.…”

“…This could be also lead to the rigidification of polymer chains near the GO sheets [15]. Similar trends were also observed by incorporating a small amount of GO into PVA matrix [45,48]. Table 3.…”

“…Another potential reason could be the aggregation of GO sheets in PVA matrix created new pathways for water adsorption and diffusion. Smaller free volume fraction was also obtained by adding GO into PVA matrix from other studies [45].…”

Free volume and lamellar structure of poly vinyl alcohol-nanosized BaTiO3 composite: Positron annihilation and small angle X-ray scattering study

“…The bulk properties of polymers are shown to be altered in their nanocomposites due to synergistic effects. In this regard, strong interfacial interaction is shown to be highly crucial for causing significant alteration in the bulk physical properties [10,12,14,15]. In recent years, efforts have been made to prepare polymer nanocomposites with high permittivity nanofillers like ferroelectric ceramics (Pb(Zr,Ti)O 3 , Ba 1Àx Sr x TiO 3 and BaTiO 3 ).…”