Enhancement of Mechanical Properties Upon Hydration in Copolymers of PEG and IodinatedTyrosine-derived Poycarbonates

摘要

Increase in modulus upon hydration in copolymers of desaminotyrosyl-tyrosine ethyl ester (DTE)and poly(ethylene glycol) (PEG) with iodinated tyrosines, poly(I2DTE-co-PEG carbonate)s, wasinvestigated by varying the fraction and the molecular weight of the hydrophilic PEG component.Water, as expected, acts as plasticizer in polymer with PEG content < 15 wt% and > 30 wt%. But,water has the opposite effect in iodinated polymers with moderate PEG contents, between 15 to 20wt%: it enhances the Young's modulus. The strength and modulus of hydrated poly(I2DTE-co-15%PEG_(2K) carbonate)s increased by as much as fifteen fold upon hydration. While the decrease in themechanical properties in most polymeric materials with diluents such water is due to the solvent-induced swelling, the increase in strength and modulus that is observed is most likely due to thereinforcing effect of the increased cross-linking efficiency of the hydrated PEG domains in theiodinated polymer.