Block copolymers were prepared by the direct polycondensation of an aqueous lactic acid solution on monomethoxy or dihydroxyl poly(ethylene glycol) (PEG) in the absence of a catalyst. The resulting poly(lactic acid) (PLA)-PEG diblock and PLA-PEG-PLA triblock copolymers were characterized by various analytical techniques, including matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS), gel permeation chromatography, and H-1-NMR. The molecular structure between PLA-PEG and PLA-PEG-PLA could be distinguished after the calculation of the repeat unit masses and end-group masses through the MALDI-TOF MS spectra. Interestingly, both copolymers could serve as a hydrophilic emulsifier to stabilize the squalene/water interfaces and yield narrowly distributed oil-in-water nanoparticles. In contrast, the pre-polymer PEG failed to stabilize the squalene/water interface under the same homogenization conditions. These features are of great interest for applications as bioactive agent delivery, especially for candidate vaccine antigens and lipophilic anticancer drugs.
Date:
2009-10
Relation:
Journal of Applied Polymer Science. 2009 Oct;114(1):509-516.
