Synthesis and Water Sorption of Various End-Capped Polylactides

Polylactide(PLA) is a bio-based polymer used for packaging and bottle applications. However, the application is now limited because water sorption can affect physical properties such as buckling effect of water bottle. To improve moisture barrier properties, end-capped PLA samples with various aliphatic hydrophobic groups were synthesized by ring-opening polymerization of L-lactide and D,L-lactide in the presence of triethylaluminum as a catalyst. The chemical structure and molecular weight of end-capped PLAs were determined by NMR and GPC. Quartz Crystal Microbalance and Heat conduction Calorimeter (QCM/HCC) was used to measure water sorption of end-capped PLAs.

Palmityl-PLLA10k-Acetoxy showed lowest water sorption compared with water sorption of palmityl-PLLA10k-OH and palmityl-PLLA10k-palmitoxy. We investigated surface morphology of end-capped PLAs related to moisture barrier properties. States of water such as freezable and nonfreezable water associated with water sorption mechanism were analyzed by MDSC.