Tuning the Degradation Profiles of Poly(l-lactide)-Based Materials through Miscibility

摘要

The effective use of biodegradable polymers relies on the ability to control the onset of and time needed for degradation. Preferably, the material properties should be retained throughout the intended time frame, and the material should degrade in a rapid and controlled manner afterward. The degradation profiles of polyester materials were controlled through their miscibility. Systems composed of PLLA blended with poly[(R,S)-3-hydroxybutyrate] (a-PHB) and polypropylene adipate (PPA) with various molar masses were prepared through extrusion. Three different systems were used: miscible (PLLA/a-PHB5 and PLLA/a-PHB20), partially miscible (PLLA/PPA5/comp and PLLA/PPA20/comp), and immiscible (PLLA/PPA5 and PLLA/PPA20) blends. These blends and their respective homopolymers were hydrolytically degraded in water at 37 °C for up to 1 year. The blends exhibited entirely different degradation profiles but showed no diversity between the total degradation times of the materials. PLLA presented a two-stage degradation profile with a rapid decrease in molar mass during theearly stages of degradation, similar to the profile of PLLA/a-PHB5.PLLA/a-PHB20 presented a single, constant linear degradation profile.PLLA/PPA5 and PLLA/PPA20 showed completely opposing degradation profilesrelative to PLLA, exhibiting a slow initial phase and a rapid decreaseafter a prolonged degradation time. PLLA/PPA5/comp and PLLA/PPA20/comphad degradation profiles between those of the miscible and the immiscibleblends. The molar masses of the materials were approximately the sameafter 1 year of degradation despite their different profiles. Theblend composition and topographical images captured at the last degradationtime point demonstrate that the blending component was not leachedout during the period of study. The hydrolytic stability of degradablepolyester materials can be tailored to obtain different and predetermineddegradation profiles for future applications.