Controlled Synthesis And Property Of Novel Cellulose Derivatives Bearing Alkoxy Phenylcarbamates

Polysaccharide-based chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC), especially phenylcarbamate derivatives of cellulose, are well-known to exhibit excellent chiral recognitions in recent decades. The chiral recognition abilities of these derivatives can significantly change depending on the substituents of the aromatic rings and are quite low when bearing fairly polar ones which mechanism hasn't been carried out until now. Longer substituents usually can make a difference on chiral recognition abilities and liquid crystal properties by changing the higher-order structures. Therefore, in order to investigate the influence of alkoxy phenylcarbamates and longer alkoxy substituents on chiral recognition abilities and liquid crystal properties, a series of novel cellulose derivatives were synthesized in this study and their chiral recognition mechanism is further elucidated on the molecular level.Three kinds of phenyl isocyanates and series of cellulose phenylcarbamate derivatives bearing para-alkoxy substituents were synthesized respectively by reacting with triphosgene and classical esterification, then their structures were characterized by fourier transform infrared (FT-IR) and nuclear magnetic resonance (1H NMR and 13C NMR). The CSPs based on the obtained cellulose derivatives were prepared after coating on the aminopropyl silica gel,and the chiral columns were prepared by slurry method for HPLC. The coating ratios of CSPs were analyzed by thermogravimetry analysis (TGA). The chiral recognition abilities of cellulose derivatives were evaluated through enantioseparation of several chiral compounds on the novel CSPs by normal- and reversed-HPLC in different chromatographic conditions,with the liquid crystal properties through differential scanning calorimetry (DSC) and polarizing microscope (POM). The effect of alcohols, polarity and length of the alkoxy substituents on the chiral recognition abilities was further investigated.It can be found that novel cellulose phenylcarbamate derivatives bearing alkoxy substituents exhibited well chiral resolutions to most chiral compounds, comparable or higher chiral recognition abilities than some commercial columns, but lower chiral recognition abilities when bearing longer alkoxy substituents. The higher-order structures of cellulose phenylcarbamate derivatives, which can be influented by polar alkoxy substituents, might change not only the enantioselective interactions or chiral recognition abilities,but also the liquid crystal properties.