Calorimetric characterization of membrane materials based on polyvinyl alcohol

There is ample scope for modification of polyvinyl alcohol (PVA) to derive diverse range of properties because of the presence of hydroxyl group in its chain. In the present work, PVA has been modified to carboxymethylated polyvinyl alcohol (CPVA) — a carboxy-functionalized membrane material. Generally the cohesive energy density has incremental influence on the melting point and mechanical strength of a material but in this case of CPVA even though theoretical cohesive energy density of CPVA is lower than that of PVA but paradoxically its mechanical strength was found to be higher than that of PVA (∼202 vis-à-vis 207°C and ∼174 vis-à-vis ∼58 MPa, respectively). Calorimetric evaluation along with the energy balance concept have provided meaningful information to justify such paradoxical feature as a result of the dominating role of intermolecular hydrogen bonding in CPVA to compensate for its relatively lower cohesive energy density typically 0.05 J m^−3/2. Thermal analysis has been made to examine the role of PVA and its carboxymethylated derivative (CPVA) towards moisture. It was observed that PVA membrane surface became sticky on exposure to water at 30°C for a period of 30 min, whereas under the same condition CPVA counterpart remained practically unaffected.