Article ID Journal Published Year Pages File Type
1218 Acta Biomaterialia 2012 10 Pages PDF
Abstract

Distribution of water in three classes of biomedically relevant and degradable polymers was investigated using small-angle neutron scattering. In semicrystalline polymers, such as poly(lactic acid) and poly(glycolic acid), water was found to diffuse preferentially into the non-crystalline regions. In amorphous polymers, such as poly(d,l-lactic acid) and poly(lactic-co-glycolic acid), the scattering after 7 days of incubation was attributed to water in microvoids that form following the hydrolytic degradation of the polymer. In amorphous copolymers containing hydrophobic segments (desaminotyrosyl-tyrosine ethyl ester) and hydrophilic blocks (poly(ethylene glycol) (PEG)), a sequence of distinct regimes of hydration were observed: homogeneous distribution (∼10 Å length scales) at <13 wt.% PEG (∼1 water per EG), clusters of hydrated domains (∼50 Å radius) separated at 24 wt.% PEG (1–2 water per EG), uniformly distributed hydrated domains at 41 wt.% PEG (∼4 water per EG) and phase inversion at >50 wt.% PEG (>6 water per EG). Increasing the PEG content increased the number of these domains with only a small decrease in distance between the domains. These discrete domains appeared to coalesce to form submicron droplets at ∼60 °C, above the melting temperature of crystalline PEG. The significance of such observations on the evolution of micrometer-size channels that form during hydrolytic erosion is discussed.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (81 K)Download as PowerPoint slide

Related Topics
Physical Sciences and Engineering Chemical Engineering Bioengineering
Authors
, , , , ,