Physical structure contributions in pH degradation of PEO-b-PCL films

Abstract

Poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) is an intriguing candidate for hydrophobic drug encapsulation and controlled release into the body as a biocompatible, amphiphilic block copolymer. In this study, a variety of characterization techniques, including DSC, NMR, and SEM, were employed to investigate the degradation of PEO-b-PCL films within aqueous environments. Previous work has shown that the degradation of these films is accelerated in both basic and acidic environments; however, it is important to develop a better understanding of degradation rate as it relates to the physical structure of the films. To this end, the degree of crystallinity of each block within PEO-b-PCL films was manipulated intentionally by varying the molecular weight and rate of cooling from melt. The data indicated that molecular weight, cooling rate, and pH all have substantial effects on the rate of degradation of the films and on the composition of the degradation products over time. In general, increasing the mass fraction or degree of crystallinity of PCL leads to slower degradation. Further, crystallization of the PEO block hinders buffer penetration, slowing degradation, while a higher mass fraction of amorphous PEO accelerates the erosion of these films. This insight can help inform efforts to fine-tune the encapsulation and delivery of hydrophobic pharmaceutical compounds.