title: Organogelation of diacetylene cholesteryl esters having two urethane linkages and their photopolymerization in the gel state.
abstract: Various diacetylene cholesteryl esters having two urethane linkages were synthesized to study the relationship between their gelation properties and chemical structures. Most of these compounds form organogels in cyclohexane, and some compounds gelatinized hexane, diethyl ether, N,N-dimethylformamide, and ethanol. The cholesteryl moieties play an important role in gel formation, but IR spectroscopic measurements show that the main driving force for gelation is hydrogen bonding of the urethane groups. Upon UV irradiation, most of the gels polymerized to give polydiacetylenes, with concomitant changes from colorless to a variety of hues, such as dark blue, orange, and pink. The polymerization proceeds efficiently in cases where the gels change color to dark blue. The polymerization reached 52% chemical yield, with the quantum yield estimated to be at least 54. Solid-state NMR spectroscopy confirmed that polymerization in the gel state proceeds via 1,4-addition.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan. j.nagasawa@aist.go.jp
authors.forename: Jun'ichi
authors.initials: J
authors.lastname: Nagasawa
authors.forename: Masabumi
authors.initials: M
authors.lastname: Kudo
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Hayashi
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tamaoki
mesh_terms: D000114:Acetylene / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000528:radiation effects; D002788:Cholesterol Esters / Q000138:chemical synthesis* / Q000737:chemistry / Q000528:radiation effects; D005782:Gels / Q000737:chemistry; D008027:Light; D015394:Molecular Structure; D010316:Particle Size; D010777:Photochemistry; D013499:Surface Properties; D014520:Urethane / Q000737:chemistry*
chemical_list: D002788:Cholesterol Esters; D005782:Gels; D014520:Urethane; D000114:Acetylene