Atomic scale assessment of PVDF based Composite Membranes for membrane distillation

A computational approach is used to investigate interfacial electronic interaction and optical response in plasmon-assisted membranes. A combination of density functional theory (DFT), time-dependent density functional theory (TDDFT) and molecular dynamic simulation (MDS), was implemented to elucidate the PVDF membrane incorporated with boron nitride (BN) and tungsten nitride (WN) nanofillers. Existing plasmonic membrane studies do not address atomic-scale behaviour at polymer-nanofiller interactions. DFT calculation reveals that electronic band gap of PVDF is about 7.3 eV, while that of the PVDF + BN + WN composite is about 0.08 eV, these findings indicates that a pronounced narrowing of the gap and enhances the interfacial charge transfer upon introduction of BN and WN. The TDDFT-calculated optical spectrum of the PVDF + BN + WN composite shows a strong absorption peak at 5.280 eV (234.8 nm), corresponding to plasmon-like excitation in WN nanofillers. The estimated optical band gap of 1.080 eV indicates quasi-metallic behaviour with efficient low-energy photon absorption. This strong near-infrared absorption highlights the suitability of the composite for plasmon-assisted membrane distillation applications. Molecular dynamic simulation shows that BN and WN remain stably dispersed within the PVDF matrix, with persistent short-range interfacial contacts and thermally driven polymer rearrangements preserving interfacial coupling at finite temperature.