Blends of aliphatic polyesters: V non-enzymatic and enzymatic hydrolysis of blends from hydrophobic poly( l-lactide) and hydrophilic poly(vinyl alcohol)

Abstract

Phase-separated blend films from poly( l-lactide) (PLLA) and poly(vinyl alcohol) (PVA) with different PVA contents were prepared by solution-casting and subsequent melt-quenching of PLLA-rich phase, and the effects of addition of the hydrophilic water-insoluble PVA on the non-enzymatic and enzymatic hydrolysis of hydrophobic PLLA were investigated. The results of gravimetry, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), tensile testing, and scanning electron microscopy (SEM) exhibited that the non-enzymatic and enzymatic hydrolysis of PLLA was accelerated by the presence of PVA and both the hydolysis rates increased dramatically with a rise in PVA content in the blend films. The enhanced non-enzymatic hydrolysis of PLLA in the blend films is ascribed to the increased water concentration around PLLA molecules and water supply rate to them by the presence of hyrophilic PVA both in PLLA-rich and PVA-rich phases, while the accelerated enzymatic hydrolysis of PLLA in the blend films is due to occurrence of enzymatic hydrolysis at the interfaces of PLLA-rich and PVA-rich phases inside the blend films as well as at the film surfaces.