| Co-Investigator(Kenkyū-buntansha) |
UTE Koichi Osaka University, Faculty of Engineering Science, Assistant Professor, 基礎工学部, 助手 (30176713)
KITAYAMA Tatsuki Osaka University, Faculty of Engineering Science, Associate Professor, 基礎工学部, 助教授 (60135671)
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| Research Abstract |
Highly isotactic(it-) and highly syndiotactic(st-) oligomers of methy1 methacrylate (MMA) were prepared by the stereospecific living polymerizations of MMA.The oligomers were separated into the individual homologues from the 10mer to the 100mer (C_<504>H_<810>O_<200> = 10,070) by means of preparative supercritical fluid chromatography (SFC). The molecular weight dependence of the glass transition temperature for the it- and st- oligomer series was investigated using the samples of the 19 - 50mers. The it-oligomers with the degree of polymerization higher than 30 crystallized by annealing, and the melting endotherms of the uniform oligomers were sharper than that of the oligomer having molecular weight distribution. The it-5mer and st-4mer gave single crystals, and the crystal structures were determined by X-ray analysis. When the it-50mer and st-50mer were mixed and subjected to the GPC using THF as eluent, a sharp elution peak due to the stereocomplex between the 50mers was observed at the elution volume corresponding to the 100mer ; on the basis of the GPC analysis of the oligomer mixtures, the complexation stoichiometry and the mechanism of the complexation were studied.
Purely it-oligomers of chloral (CCl_3CHO) with a structure RO[CH(CCl_3)O]_nR' were prepared by the oligomerization of chloral initiated with RONa and terminated with R'X.The oligomers from the 2mer to the 9mer were isolated individually as single crystals by GPC or SFC.Each it-oligomer having t-butyl and acetyl groups as R and R', respectively, could be resolved into the optical antipodes by HPLC.The (-)-5mer([alpa]_D = -23.7 ) was found to be the (R,R,R,R,R)-isomer having a right-handed 4/1 helical structure by X-ray analysis. The it-7mer and it-8mer carrying a methyl group at both ends, which are the meso isomers, could also be optically resolved based entirely on conformational chirality (one-handed helix).
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