The physico-mechanical and structural characteristics of blend film of poly (vinyl alcohol) with biodegradable polymers as affected by disorder-to-order conformational transition

The binary blend films of poly (vinyl alcohol) (PVA) were prepared with selected biodegradable polymers (Na-alginate, gelatin, chitosan, k-carrageenan and carboxymethyl cellulose) at the point of their chain entanglement. The water resistance, water vapor permeability and mechanical assays were considered as a benchmark to select the superior blend film. The highest water resistant and water barrier property belonged to the blend that contains k-carrageenan. Introducing the biodegradable polymers into PVA led to an increase in tensile strength, among which k-carrageenan being further effective than the others. Accordingly, the influence of conformational change of k-carrageenan chains from disorder-to-order mode on PVA matrix was monitored by hydrophobicity assay, FT-IR, FE-SEM and XRD. The conformational change of k-carrageenan increased PVA hydrophobicity. k-carrageenan chains which are presented as the ordered form, noticeably decreased the surface free energy of the PVA-based film. The emergence of new characteristic bands regarding k-carrageenan found in the fingerprint region of PVA at above k-carrageenan coil-overlap concentration. FE-SEM exhibited that PVA surface became uniform along with the disappearance of cracks after k-carrageenan inclusion. The pronounced k-carrageenan peak appeared in diffraction pattern of PVA after the conformational transition of k-carrageenan chains. (C) 2016 Elsevier Ltd. All rights reserved.