Effect of supermolecular structure of cellulosic materials on chiral discrimination

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Studies on the hysteretic effect of coating were investigated using cellulose triphenylcarbamate as a chiral separating phase of chiral support for HPLC. According to the previous paper by Shibata et al., the different kinds of coating solvent resulted in the different elution order of enantiomers with the use of cellulose acetate as a chiral separating phase. For further investigations of the relationship between coating solvents and chiral selecting polymers, we have selected the combination of cellulose trhiphenylcarbamate and its organic solvents reported to from alyotropic liquid crystal.Firstly, we have synthesized cellulose triphenylcarbamate according to the method of Schroeder and his coworker, dissolved it in the organic solvent such as methylpropylketone (MPK), diglyme, and e.t.c., and checked if the system forms a cholesteric liquid crystal. Because the resultant solution of cellulose derivative seemed to show a poor cholesteric nature, we repeated the synthetic reaction fo … More r the already derivatized cellulosic material and obtained typical cholesteric liquid crystals. Degree of polymerization could have changed during the repeated reaction. Cholesteric nature was recognized by observations using polarizing microscope, and the measurements of spectrum of UV, ORD.Then, the dilute solution (10wt%) of cellulose triphenylcarbamate either in MPK or in diglyme was poured onto porous silica gel (mean particle size 7 μm and mean pore diameters 100 nm), and the solvent was removed. The evaporation of the solvent was performed ether in a draft chamber for the MPK or in a vacuum oven at 30℃ for the diglyme, and the duration required for the evaporation was more than 1weeks for both solvents. After obtaining the chiral support, we prepared the laboratory-made columns for optical resolution by packing it into stain-less steel columns, and estimated their chiral recognizing ability.The chiral resolving column prepared by using MPK as a coating solvent showed a prominent resolving power and comparable to the commercial column in terms of resolution factors (α) and theoretical plate numbers, although the other column showed poor results due to the insufficient evaporation of the coating solvent. The order of elution for enantiomer was found to be the same among the tested colums. Less