Molecular dynamics analysis of PVA-AgnP composites by dielectric spectroscopy

Abstract

The molecular dynamics of PVA/AgnP composites were studied by dielectric spectroscopy (DS) in the 20300C temperature range. Improper water elimination leads to misinterpretation of thermal relaxations in PVA composites in agreement with the previous report for pristine PVA. The evaporation of water and its plasticizing effect are more evident in pure PVA confirming the existence of strong interaction between OH groups of PVA chains and AgnP. Dry films show a single nonlinear VFT dependence (from 45C until melting) associated to the α-relaxation and, therefore, to the glass transition phenomenon and from dielectric measurements, the T g of composites vary from 88°C for pristine PVA to 125°C for PVA/AgnP (5wt). Below 45°C, dry films exhibit a single Arrhenius behavior showing a 3D hopping conductivity as explained based on the variable range hopping model. PVA/AgnP composites have higher conductivity compared to pristine PVA, and it increases as AgnP weight percent increases. Finally, DMA measurements support the statement that a secondary relaxation was erroneously assigned as the glass transition of PVA and composites in previous reports. Copyright © 2012 J. Betzabe Gonzlez-Campos et al.