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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 28, Number 5
BKCSDE 28(5)
May 20, 2007 

Conformational Transition of Poly(γ -benzyl-L-glutamate)-Poly(ethylene glycol) Block Copolymers in Bulk
Young-Wook Choi, Youngmi Park, Jaebum Choo, Chong Su Cho, Daewon Sohn*
Block copolymer, Rod-coil copolymer, PBLG-PEO, Smectic C phase, Aggregation energy
The bulk properties of poly(γ-benzyl-L-glutamate)-poly(ethylene glycol), PBLG-PEO, diblock copolymer were investigated. The helical transition from 7/2 to 13/5 for pure PBLG was at 120 oC while those of GE-1 and GE-2, which contain flexible PEO block 40 wt% and 60 wt% respectively, were shown at 135℃ on DSC experiments. FT-IR and XRD experiments were shown that the diblock copolymers maintained their α-helical structure in the temperature range between 25℃ and 175℃. Increasing relative size of coil part resulted in the increase of intermolecular packing distances. Due to well-maintained helical structure, lyotropic LC phases were observed for the PBLG-PEO block copolymer by the polarized optical microscope (POM). Especially, GE-3 copolymer, which has 12.5 wt% PEO contents, showed the smectic C phase. The competition of favorable aggregation energy between rod-rod and coil-coil, and unfavorable aggregation energy of rod-coil give rise to change the supramolecular structure in mixed solvent.
795 - 799
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