Synthesis of Poly(L(+) Lactic Acid) by Polycondensation Method in Solution
The disposal problem due to non-degradable petroleum-based plastics has raised the demand for biodegradable polymers. Poly(lactide) (PLA) is a biodegradable aliphatic polyester derived from 100% renewable resources, such as corn and sugar beets. Moreover, it has unique physical properties that make it useful in diverse applications including paper coating, fibers, films, and packaging. In this work, the results of the synthesis of high molar weight poly(L(+) lactic acid) (PLA) which is able to thermally crystallize have been described. The synthesis of poly(L(+) lactic acid) was carried out in a solution of p-xylene. Tin(II) chloride was used as catalysts in a quantity of 1.0 wt% calculated on the monomer. Polycondensation was carried out over a period from ten to over 20 h. The resulting poly(L(+) lactic acids) were characterized by FT-IR, DSC and the GPC. The molecular weight of PLLA reached as high as 26000. FTIR spectra of PLLA were analyzed to determine the configuration of the PLLA. The main byproduct of condensation polymerization is cyclo-polyester. The glass transition temperature of PLA after is 46.25°C. PLA after the recrystallization does not show glass transmission temperature because the crystallinity is more than 40%.
KeywordsLactic Acid Azeotropic Distillation Condensation Polymerization Main Byproduct Direct Polycondensation
Funding for this project was provided by the USDA; Mrs. Nicole Whiteman of NatureWorks provided technical advice.