Hydrolytic Degradation of Polyester Blend Monolayers at the Air/Water Interface: Effects of a Slowly Degrading Component

The hydrolytic behavior of monolayers of biodegradable [poly( l -lactide)/poly(ε-caprolactone)] ( l -PLA/PCL) blends spread at the air/water interface is studied to identify the relative rate of hydrolytic degradation of each component when exposed to a basic subphase. As the hydrolysis time increases, the isotherm recorded from ( l -PLA/PCL) blend monolayers was found to be similar to that of PCL homopolymer; this is likely due to the preferred hydrolysis of l -PLA. The rate of hydrolysis was recorded by a change of occupied area when the monolayer is maintained at a constant surface pressure. The hydrolysis of the blend in a basic condition was much faster than that of each homopolymer, regardless of the composition, arising from a dilution effect on the concentration of l -PLA monolayers. From the deviation behavior ( D ) between the arithmetic average and experimental values, blends with compositions less than 50 mol % l -PLA showed the maximum dilution effect ( D t = 0.11 t, where t is hydrolysis time) whereas high l -PLA compositions (≥75 mol % l -PLA) showed a smaller effect.