title: Two types of two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers.
abstract: Two-component gels formed from pseudoenantiomeric ethynylhelicene oligomers in toluene exhibited two different properties depending on difference in numbers of helicenes in the two components. The combinations (M)-5/(P)-4, (M)-6/(P)-4, and (M)-7/(P)-4, which contained oligomers with comparable numbers of helicenes, formed transparent gels (Type I gels). The combinations (M)-6/(P)-3, (M)-7/(P)-3, and (M)-8/(P)-3, which contained oligomers with considerably different numbers of helicenes, formed turbid gels (Type II gels). Negative Cotton effects were observed for the Type I gels in the region between 350 and 450 nm, and were positive for the Type II gels, despite the use of (M)-oligomers for the longer components. UV/vis exhibited absorption maxima at 350 nm for the Type I gels and at 338 nm for the Type II gels. Different behaviors in gel formation processes were observed by fluorescence studies. Atomic force microscopy analysis showed fiber structures of 25-50 nm diameter for Type I gels and bundles of 100-150 nm diameter for Type II gels. The stoichiometry in gel formation also differed: The Type I gels showed 1:1 stoichiometry of the two components; the Type II gels showed no 1:1 stoichiometry, likely 1:2 stoichiometry. Using the Type I and II gels, two-layer gel systems were constructed.
authors: Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Sendai 980-8578, Japan.
authors: Koji
authors: K
authors: Yamamoto
authors: Naohiro
authors: N
authors: Oyamada
authors: Marie
authors: M
authors: Mizutani
authors: Zengjian
authors: Z
authors: An
authors: Nozomi
authors: N
authors: Saito
authors: Masahiko
authors: M
authors: Yamaguchi
authors: Motohiro
authors: M
authors: Kasuya
authors: Kazue
authors: K
authors: Kurihara
mesh_terms: D005782:Gels; D008958:Models, Molecular; D008968:Molecular Conformation; D011083:Polycyclic Compounds / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013237:Stereoisomerism; D014050:Toluene / Q000737:chemistry
chemical_list: D005782:Gels; D011083:Polycyclic Compounds; D011108:Polymers; C560958:ethynylhelicene; D014050:Toluene