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

Abstract

The hydrolytic behavior of monolayers of biodegradable [poly(l-lactide)/poly( -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 (Dt ) 0.11t, where t is hydrolysis time) whereas high l-PLA compositions (g75 mol % l-PLA) showed a smaller effect.

Effect of processing conditions and lignin content on thermal, mechanical and degradative behavior of lignin nanoparticles/polylactic (acid) bionanocomposites prepared by melt extrusion and solvent casting

“…The influence over the degradation process strongly depends on the hydrophilicity/hydrophobicity and dispersion of the nanoparticles. Moreover, a delayed biodegradability due to the improved barrier properties of the nanomaterials was previously observed, which could hinder the water diffusion through the bulk [42]. The study of the disintegration in composting conditions of PLA and PLA bionanocomposites was carried out to evaluate the effect of the addition of LNPs and processing methods on the disintegrability properties of the PLA matrix.…”

Hydrolytic Degradation

“…On the other hand, Mallard e et al [239] reported that oligomeric PDLLA (M n ¼ 1100 g/mol) enhanced the alkaline hydrolytic degradation of poly(3-hydroxyoctanoate). Lee et al [14,236] found that the dilution effect of slowly degrading PCL on rapidly degrading PLLA increased the alkaline hydrolytic degradation of PLLA/PCL blend monolayers with PLLA contents below 50%. Similarly, regarding bulky PLLA-based blends, the incorporation of PCL or P(LLA-co-CL) increased the total NHD of the blends as traced by molecular weight, and the enhancing effect was higher for P(LLA-co-CL) [27,237].…”

study on hydrolytic kinetics of Langmuir monolayers of biodegradable polylactide derivatives

“…[10][11][12][13][14][15] The low molecular weight oligomers and monomers generated by hydrolysis dissolve into water. This would result in a change in the occupied area if the monolayer is maintained at a constant surface pressure.…”

“…This behavior implies that the carboxyl acid group, not the alcohol group generated by the chain cleavage of ester bond is mainly related to the molecular loss likely due to the formation of carboxyl acid salts with sodium ion and then the increase of the solubility into subphase. [13][14][15] Therefore, the diffusion of acid fragments away from the reacting monolayer may well be the rate determining step. Figure 2 shows the surface pressure-area isotherms for dl-PLA monolayers on subphase of pH 10.5 measured with different pause times of 1 and 2 hr.…”

“…[12][13][14][15] In this study, the hydrolytic degradation of modified polylactides has been systematically investigated at the air/water interface as a function of subphase pH, concentration of degradation medium (alkaline or enzyme), and degradation time.…”