Studies on Structure and Physical Properties of Poly (lactic acid)-Based Biodegradable Polyesters

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The purposes of this study were(1)to develop new methods such as surface modification (alkaline treatment, biodegradable polymer coating), blending (hydrophilic biodegradable polymers, enantiomeric PLAs, and inorganic particles), and pore formation by the use of phase separation, to control physical properties and biodegradability of the poly (lactide) s [poly (lactic acid) s (PLAs)]-based biodegradable polyesters,(2)to investigate biodegradation mechanisms of the prepared materials, and(3)to develop a novel method for recycling PLAs to their monomers by the use of high-temperature and high-pressure water. It was found for biodegradable polyesters including PLAs that surface modification is effective both for acceleration and deceleration of their biodegradation without erosion of the core part of the materials, that blending is inclined to accelerate their biodegradation when the blends are phase-separated, and that pore formation is effective both for preparation of soft materials and acceleration of their biodegradation. Moreover, "restricted amorphous region" between the crystalline regions in spherulites was found to be much more hydrolysis-resistant than "free amorphous regions" outside spherulites and hydrolysis in the melt by the use of high-temperature and high-pressure water was shown to be a powerful method to recycling poly (L-lactide) [poly (L-lactic acid)] to L-lacticacid.