In Vitro Hydrolysis of Blends from Enantiomeric Poly(lactide)s. 2. Well-Stereocomplexed Fiber and Film.

Abstract

Well-stereocomplexed 1:1 fiber and film were prepared from poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) by the melt-spinning and hot-drawing and the solution-casting methods, respectively, and their hydrolysis in phosphate-buffered solution (pH 7.4) at 37°C was investigated. The decrease rates of weight remaining, tensile strength, elongation-at-break, and melting temperature (Tm) during hydrolysis were higher for the fiber than for the film. The accelerated hydrolysis of the fiber was ascribed to the high concentrations of the catalytic oligomers and monomers during hydrolysis, resulting from their high initial concentration caused by thermal degradation during melt-spinning and hot-drawing and from their retarded elution from the fiber due to the bulky microscopic shape. The changes in Tm, crystallinity, and weight remaining suggest that the hydrolysis of the fiber proceeds mainly via bulk erosion mechanism, that the chain cleavage of the fiber occurred in the crystalline region and at the folding surface as well as in the other amorphous region, and that lamella thickening of the film took place without significant chain cleavage in the crystalline region and at folding surface.