Monolayer formation of PBLG-PEO block copolymers at the air-water interface.
Physicochemical properties of PBLG (poly(gamma-benzyl-l-glutamate))-PEO (poly(ethylene oxide)) diblock copolymers composed of PBLG as the hydrophobic rod component and PEO as the hydrophilic component were investigated at the air-water interface. Surface pressure-area isotherms obtained by the Wilhelmy plate method provide several variables such as molecular size, compressibility of PEO, and the free energy change of the PBLG-PEO block copolymer. GE-1 (M(w) of PBLG:PEO=103,700:12,000), with a relatively longer rod, has negative temperature effects and GE-3 (M(w) of PBLG:PEO=8400:12,000), with a relatively shorter rod, shows a positive temperature effect because of the large entropy loss. These competitions were based on the block size of PBLG and PEO and were affected by various microstructures of the PBLG-PEO diblock copolymer. Monolayer aggregations transferred onto mica from the air-water interface were analyzed with AFM. AFM images of GE-1 monolayers show cylindrical micelles, but the self-assembled structure has many large domains. The monolayer of GE-2 (M(w) of PBLG:PEO=39,800:12,000), which has a medium size rod, forms a spherical structure at the air-water interface. Monolayers of GE-3, with a short rod length, form bilayer structures. These results demonstrate that the microstructures of PBLG-PEO diblock copolymers are related to free energy changes between rod and coil blocks.
Park
Youngmi
Y
Department of Chemistry, Hanyang University, Seoul 133-791, South Korea.
Choi
Young-Wook
YW
Park
Sangwook
S
Cho
Chong Su
CS
Fasolka
Michael J
MJ
Sohn
Daewon
D
D000388:Air; D019277:Entropy; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force / Q000379:methods; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000138:chemical synthesis / Q000737:chemistry*; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D012680:Sensitivity and Specificity; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D008567:Membranes, Artificial; C104155:poly(gamma-benzylglutamate)poly(ethylene oxide); D014867:Water; D011099:Polyglutamic Acid; D011092:Polyethylene Glycols