Abstract
A liquid, biocompatible polyester based polymer, which could facilitate injectable formulations by simple mixing with the active substance (drug) is much needed by the pharmaceutical companies. A favourite candidate is polylactic acid (PLA) which is biocompatible and biodegradable. However PLA is solid with high crystallinity. Thus, in this research, hydroxylauric acid (HOLA) was copolymerized with lactic acid (LA) in different ratios by polycondensation technique at 180 °C, without a metal catalyst and avoiding the formation of interfering lactides, to provide a liquid polyester. The copolymers molecular weights were determined by Gel Permeation Chromatography (GPC) and their physical states indicated as solid or liquid were noted. The structures as polyesters were confirmed by FT-IR and 1H NMR spectroscopy. Poly(HOLA:LA) products from reactant ratios 0:100 is solid, while ratios of 20:80, 40:60 are mixed (paste) and 60:40, 80:20 and 100:0 are liquids. Thus, the liquid polyesters from the polycondensation of HOLA and LA without catalyst were picked as potential candidates for dissolving hydrophobic drugs that could be used as injectables in controlled drug delivery experiments.
Highlights
Because of the interesting material properties of poly(lactic acid) polylactic acid (PLA) and its copolymers, such as biodegradability and as an example of sustainable materials being obtained from natural resources, extensive reports on it and its copolymers can be found in literature
As the reaction ratio was increased with the monomer hydroxylauric acid (HOLA), the greater the polymer’s tendency to be in the liquid (HOLA:LA) Formulation
Lactic acid derived polyester in the liquid form was prepared by reacting lactic acid with methylene rich hydroxylauric acid in different ratios such as (0:100, 20:80, 40:60, 60:40, 80:20 and 100:0)
Summary
Because of the interesting material properties of poly(lactic acid) PLA and its copolymers, such as biodegradability and as an example of sustainable materials being obtained from natural resources, extensive reports on it and its copolymers can be found in literature. PLA injectable modifications are not possible without formulating the materials as micro- or nanoparticles or adding further excipients (Trimaille et al, 2005; Trimaille et al, 2007). Copolymerization can be done by ring-opening polymerization (ROP) This method is used to produce biomedical grade PLA with controlled molecular weight and narrow polydispersities (Trimaille et al, 2004). While an often mentioned disadvantage of polycondensation is its limitation to lower molecular weight products with higher polydispersities in comparison with ROP, this is not a disadvantage for the intended injectables. Significantly higher molecular weight polyesters by efficient melt polycondensation and purification method were done by Asmus et al (2011)
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