Poly (lactic-co-glycolic acid) (PLGA) copolymers have been broadly used in controlled drug release applications. Because these polymers are biodegradable, they provide an attractive option for drug delivery vehicles. There are a variety of material, processing, and physiological factors that impact the degradation rates of PLGA polymers and concurrent drug release kinetics. This work is intended to provide a comprehensive and collective review of the physicochemical and physiological factors that dictate the degradation behavior of PLGA polymers and drug release from contemporary PLGA-based drug-polymer products. In conjunction with the existing experimental results, analytical and numerical theories developed to predict drug release from PLGA-based polymers are summarized and correlated with the experimental observations. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1692-1716, 2017.

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Polylactide (PLA) is a bio-based, biodegradable polymer, which is derived from lactic acid and has numerous potential applications, some of which are limited by its moisture barrier and thermal properties. Prior studies have been inconsistent about how moisture sorption in PLA varies with crystallinity and molecular weight. This research is a systematic study of how moisture sorption in PLA depends on molecular weight and aliphatic content via end-group modification. PLA with varying aliphatic content was synthesized by ring-opening polymerization of L-lactide initiated with different longchain aliphatic alcohols. The terminating end groups were also modified from hydroxyl to acetoxy to eliminate hydrophilic end groups. Molecular weight was controlled by varying the ratio of L-lactide monomer to alcohol initiator, and triethylaluminum was used as the catalyst for precise control over molecular weight. The molecular weight and end-group compositions were verified by gel permeation chromatography and nuclear magnetic resonance. Moisture sorption of the modified PLA samples was measured with a quartz crystal microbalance. Quartz crystal microbalance experiments revealed that both molecular weight and aliphatic content contributed to the sorption properties of PLA.

Water sorption into polylactide (PLA) and polylactide‐montmorillonite (PLLA‐MONT) composites containing 5 wt % of montmorillonite (MONT) under different heat treatment conditions was studied using the quartz crystal microbalance/heat conduction calorimetry (QCM/HCC) technique. Results showed that water sorption in neat polymer films and composite films increased with heat treatment temperature up to 120 °C. Differential scanning calorimetry was used to measure the glass‐transition temperature and isothermal crystallization kinetics of all samples. The mobility of the amorphous domain in all samples increased with heat treatment temperature, indicated by the decrease in glass‐transition temperature. PLA composites crystallized at a much faster rate than neat PLA did because MONT acted as a nucleating agent. Under the same heat treatment condition, water sorption in PLLA‐MONT composites was always higher than that in neat PLA due to the presence of the hydrophilic hydroxyl groups on the surface of MONT particles. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011