LIPID-MEMBRANE ANALOG-IMMOBILIZED SILICA-GELS FOR SEPARATION WITH MOLECULAR RECOGNITION

The comb-shaped polymer (ODA(n)) composed of a reactive terminal group and highly-orienting side-chain groups was prepared by telomerization using 3-mercaptopropyl trimethoxysilane and octadecylacrylate. The po lymer was readily immobilized onto porous silica gels through a termin al reactive group. DSC indicated that the silica-supported polymer (Si l-ODA(n)) underwent crystal-to-isotropic phase transition on silica ge ls at a temperature range of 28 - 47 degrees C (in the case of n = 27) in methanol. Polarity microscopic observation of the polymer showed t he phase transition included a nematic liquid crystalline state. The p acked column showed a remarkably higher separation factor for mixtures of planar aromatics (e.g. triphenylene and trans-stilbene) and non-pl anar aromatics (e.g. o-terphenyl or cis-stilbene) at room temperatures than did the conventional hydrophobic stationary phases, i.e. octadec ylated silica gels. In addition, the Sil-ODA(n) column showed remarkab le temperature dependence on both retention capacity (k') and separati on factor (alpha). The k'-temperature and alpha-temperature plots show ed distinct bending at temperatures around the phase transition temper ature of immobilized ODA(n). These results indicate that the selective retention for planar compounds is related to highly-orienting structu re formed from long-chain alkyl groups. This paper discusses the molec ular recognition mechanism using additional chromatographic behaviors and MOPAC calculation.