Abstract
Aqueous solutions of both poly(ethylene glycol)/poly(dl-lactic acid) (PEG/PDLLA) and poly(ethylene glycol)/poly(l-lactic acid) (PEG/PLLA) multiblock copolymers underwent “clear sol-to-turbid gel-to-syneresis” transitions as the temperature increased. To investigate the stereoisomeric effect on the phase behavior, PEG/PDLLA and PEG/PLLA multiblock copolymers with a similar block length and total molecular weight were carefully synthesized. Compared with the PEG/PDLLA multiblock copolymer, the PEG/PLLA multiblock copolymer showed a lower critical gel concentration, a lower sol-to-gel transition temperature, and a wider gel window. In addition, the maximal gel modulus of the PEG/PLLA multiblock copolymer (11.0 wt % in water) was 2 times larger than that of the PEG/PDLLA multiblock copolymer. X-ray diffraction spectra, transmission electron microscopic images, and polarizing optical microscopic images suggested the amorphous state for both PEG/PDLLA and PEG/PLLA multiblock copolymer thermogels. 13C NMR spectr...
Published Version
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