Biologically Safe Poly(l-lactic acid) Blends with Tunable Degradation Rate: Microstructure, Degradation Mechanism, and Mechanical Properties.

Although poly(l-lactic acid) (PLLA) is reputed to be biodegradable in the human body, its hydrophobic nature lets it persist for ca. 5.5 years. This study demonstrates that biologically safe lactide copolymers, poly(aspartic acid-co-l-lactide) (PAL) and poly(malic acid-co-l-lactide) (PML), dispersed in the PLLA function as detonators (triggers) for its hydrolytic degradation under physiological conditions. The copolymers significantly enhance hydrolysis, and consequently, the degradation rate of PLLA becomes easily tunable by controlling the amounts of PAL and PML. The present study elucidates the effects of uniaxial drawing on the structural development, mechanical properties, and hydrolytic degradation under physiological conditions of PLLA blend films. At initial degradation stages, the mass loss was not affected by uniaxial drawing; however, at late degradation stages, less developed crystals as well as amorphous chains were degradable at low draw ratio (DR), whereas not only highly developed crystals but also the oriented amorphous chains became insensitive to hydrolysis at high DR. Our work provides important molecular level results that demonstrate that biodegradable materials can have superb mechanical properties and also disappear in a required time under physiological conditions.

Change in thermal transitions and water uptakes of poly(l-lactic acid) blends upon hydrolytic degradation.

This article reports experimental data related to the research article entitled "Poly(malic acid-co-l-lactide) as a Superb Degradation Accelerator for Poly(l-lactic acid) at Physiological Conditions" (H.T. Oyama, D. Tanishima, S. Maekawa, 2016) [1]. Hydrolytic degradation of poly(l-lactic acid) (PLLA) blends with poly(aspartic acid-co-l-lactide) (PAL) and poly(malic acid-co-l-lactide) (PML) oligomers was investigated in a phosphate buffer solution at 40 °C. It was found in the differential scanning calorimetry measurements that upon hydrolysis the cold crystallization temperature (Tc ) and the melting temperature (Tm ) significantly shifted to lower temperature. Furthermore, the hydrolysis significantly promoted water sorption in both blends.