A computational and experimental investigation of TEOS-treated graphene oxide-PVA interaction: Molecular dynamics simulation and COSMO-RS insights

Abstract

This research investigates the effect of tetraethyl orthosilicate TEOS on the interaction mechanism in the hybrid polyvinyl alcohol (PVA)/graphene oxide (GO) material. PVA, PVA/Go, and PVA/GO-SiO2 are produced by the solution casting method. The TEOS treated GO is confirmed by FTIR and also suggests that PVA is chemically bonded to GO-SiO2. XRD results reveal that the crystallinity of PVA is significantly reduced with the addition of TEOS as it becomes completely amorphous and shows that the GO has a full exfoliation in the matrix. However, thermogravimetric analysis indicates that the incorporation of GO improves the thermal stability of PVA by reducing its mass-loss rate upon heating. Theoretical molecular dynamic simulations indicate that the addition of SiO2 could significantly improve the binding interaction energies from 14387 kcal/mol to 15039 kcal/mol for 6PVA/3GO and 6PVA/3GO-3SiO2 systems, respectively. These simulations also highlight the occurrence of a hydrogen bonding between PVA and GO oxygen groups and PVA and Si-OH groups. The Conductor-like Screening Model for Real Solvents (COSMO-RS) study shows the intermediary role played by SiO2, which increases the compatibility between PVA and GO. The theoretical blend study also led to the conclusion that the three molecules could be mixed over the entire temperature range. Overall, these results suggest that TEOS can be successfully employed for the functionalization of PVA/GO hybrid materials, as it strengthens the interaction of the organic and inorganic phases.