Poly (L-lactide) s (PLLA) is an interesting class of biodegradable polymers derived from renewable resources. A range of useful applications have emerged in recent years, especially, in areas related to drug delivery, biodegradable films, packaging materials and fibers. Branched polymers of L-lactide can be synthesized by a “core first” approach using known multifunctional organic compounds as initiators (e.g., dipentaerythritol (DPE). However when such organic compounds are used as core, the resulting branched polymer are not bio compatible and, hence, unsuitable for biological applications. This is because the product of hydrolysis regenerates the core, whose bio compatibility is suspect. Nevertheless branched polymers derived from such cores can be used in other applications where bio safety is not an issue. Sugars or carbohydrates are a class of naturally occurring organic molecules which are polyfunctional and, hence, can be used as a core. Branched polymers of PLLA produced using sugar as a core is ideally suitable for various biological applications. However, sugars pose a challenge to synthesis. Sugars are insoluble in organic solvents and, therefore, incompatible with ROP which are conducted in homogeneous solutions. Consequently, sugars have not been studied as a core in the ROP of L-Lactide. We have prepared a series of branched PLLA polymers using pentaerythritol and dipentaerthritol as core to yield four arms and six arm branched PLLA’s. Five arm star PLLA and PLGA polymers have also been prepared using D (+) glucose and D (+) sorbitol as the core and using an “arm first” approach and Click Chemistry. The fidelity of the arm structures is expected to be far better controlled in the “arm first” approach compared to the “core first” approach. This study provides unequivocal evidence of structures and the properties of such multi arm PLLA’s.

Synthesis, structure-property studies in lactic acid derived polymers: Multiarm branched polymers and copolymers of by "core-first" and  "arm-first" approach

249th National Meeting (2015)

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