Phase Equilibria and Structure Formation in the Polylactic-co-Glycolic Acid/Tetraglycol/Water Ternary System

This paper concerns a detailed study of the phase separation and structure formation processes that occur in solutions of highly hydrophobic polylactic-co-glycolic acid (PLGA) in highly hydrophilic tetraglycol (TG) upon their contact with aqueous media. In the present work, cloud point methodology, high-speed video recording, differential scanning calorimetry, and both optical and scanning electron microscopy were used to analyze the behavior of PLGA/TG mixtures differing in composition when they are immersed in water (the so-called harsh antisolvent) or in a nonsolvent consisting of equal amounts of water and TG (a soft antisolvent). The phase diagram of the ternary PLGA/TG/water system was designed and constructed for the first time. The PLGA/TG mixture composition with which the polymer undergoes glass transition at room temperature was determined. Our data enabled us to analyze in detail the structure evolution process taking place in various mixtures upon their immersion in harsh and soft antisolvent baths and gain an insight into the peculiarities of the structure formation mechanism active in the course of antisolvent-induced phase separation in PLGA/TG/water mixtures. This provides intriguing opportunities for the controlled fabrication of a wide variety of bioresorbable structures-from polyester microparticles, fibers, and membranes to scaffolds for tissue engineering.

Automated summary

This paper studies the phase separation and structure formation processes in hydrophobic PLGA solutions in hydrophilic TG when they contact with water. Methods including cloud point methodology, high-speed video recording, differential scanning calorimetry, and microscopy were used to analyze the behavior and structure evolution process of PLGA/TG mixtures in water and nonsolvent. The phase diagram of the PLGA/TG/water system was constructed and the composition of PLGA/TG mixture undergoing glass transition was determined. The study provides insights into the structure formation mechanism and opportunities for controlled fabrication of bioresorbable structures.