| Project/Area Number |
05044096
|
|---|
| Research Category |
Grant-in-Aid for international Scientific Research
|
| Allocation Type | Single-year Grants |
|---|
| Section | Joint Research |
|---|
| Research Institution | Osaka University |
|---|
Principal Investigator |
TERAMOTO Akio Osaka University, 理学部, 教授 (00028151)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
LIFSON Shneior Weizmann Institute of Science, ワイズマン科学研究所, (名誉)教授
PETERSON Nor 米国ポリテクニック大学, 化学科, 教授
GREEN Mark M. Polytechnic University, 化学科, 教授
SATO Takahiro Osaka University, 理学部, 助手 (10196248)
PETERSON Norman C. Polytechnic University
|
|---|
| Project Period (FY) |
1993
|
| Project Status |
Completed (Fiscal Year 1993)
|
| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1993: ¥2,000,000 (Direct Cost: ¥2,000,000)
|
|---|
| Keywords | Optical rotation / Cholesteric liquid crystal / Hydrogen-deuterium isotope effect / Chiral interaction / Polyisocyanate / Helical conformation / Helix reversal |
|---|
| Research Abstract |
1.Helical conformation of deuterium-substituted optically-active poly(hexyl isocyanate)s in dilute solution
The optical rotation of poly(hexyl isocyanate)s with deuterium substituted on the alpha- or beta-carbon in the hexyl side chain was measured in dilute solution as a function of the molecular weight and temperature. The results were fitted by Lifson et al.'s statistical thermodynamic theory, where each monomer in the polyisocyanate chain was assumed to take one of three states, the left-handed helix, right-handed helix, and helix reversal. From the fitting, the free energy difference DELTAG_h between left- and right-handed helices per monomer was estimated to be a few cal/mol, while the free energy of the helix reversal more than 3000 cal/mol. The former value indicates a very small hydrogen-deuterium isotope effect on the monomer conformation. However the latter value demonstrates the difficulty in the occurrence of the helix reversal. This difficulty accumulates the small DELTAG_
… More
h to provide a large disproportion of the left- and right-handed helical monomers in the chain.
2.Helical conformation of polyisocyanates in liquid crystalline solution
Optically inactive poly(n-hexyl isocyanate)(PHIC) exists as a racemic mixture, and it's concentrated solution forms a nematic phase. When some optically active low-molar-mass substances or copolymers consisting of some optically active and inactive isocyanate monomers were added to the nematic solution of PHIC, the solution transformed from the nematic to cholesteric. This transformation indicates the disproportion of the left- and right-handed helical states in the PHIC chain due to an accumulated chiral interaction with the optically active substances.
Although the optical rotation of the above copolymer in dilute solution depended on the monomer composition, the pitch of the induced cholesteric structure did not. This independence can be explained by the exclusion of the helix reversal state from the copolymer chain in the liquid crystalline solution. Less
|
