Preparation And Evaluation Of New Liquid-crystalline Imprinted Monolith

Liquid-crystalline molecularly imprinted polymers(LC-MIPs) are new synthetic materials with the ability of molecular recognition. In the preparation of LC-MIPs, the chemical crosslinker can be partly replaced by liquid crystal monomer.The rigid mesogenic group can soften network while preserving the memory of the template, thus LC-MIPs can hold the ability of recognition at low crossliking level.Preparation of MIPs with liquid crystal can solve the problems such as the embedding of cavities, poor imprinting efficiency and mass transfer. As a result, the LC-MIPs have great potential in MIT. In this work, two different methods were applied to prepare new type of liquid-crystalline molecularly imprinted monolith. Different synthetic conditions, chromatographic conditions and the character of MIP columns were systematically investigated. The results as follows:1 Molecular crowding is a new approach to promoting molecular imprinting more efficiently. In this work, this concept was applied to the preparation of low cross-linked liquid-crystalline imprinted monolith for stabilizing binding sites and improving molecular recognition. In present study, we firstly prepared monolithic skeleton by using trihydroxymethylpropyl trimethylacrylate, toluene and dodecanol in stainless steel column. Then the pre-polymerization mixture containing hydroquinidine(template), 4-cyanophenyl dicyclohexyl propylene(liquid-crystalline monomer), polymethyl methacrylate(macromolecular crowding agent), methacrylic acid(functional monomer) and ethylene glycol dimethacrylate(crosslinker agent)was introduced to the monolithic skeleton. Some important parameters in the preparation, i.e., ratio between template and monomer, content of macromolecular crowding agent and crosslinking density were investigated. Results showed that the resultant molecularly imprinted monolith can separate quinidine and quinine within 8min with resolution of 2.96. Furthermore, the liquid-crystalline molecularly imprinted monolith in the presence of macromolecular crowding agent showed better column efficiency and faster analysis time. The results suggested that adding macromolecular crowding agent in the preparation of low cross-linker molecularly imprinted monolith is a good way to improve the imprinting effect and performance of the column.2 Using immobilised template during preparation of molecularly imprinted monolith was confirmed can enhance imprinting effect. The monolithic skeleton was prepared with a solution of trihydroxymethylpropyl trimethylacrylate in a mixture of toluene and dodecanol in a stainless steel column. The pre-polymerization mixture containing template(2,4-diamino-6-methyl-1,3,5-triazine), immobilised template(2,4-diamino-6-(methacryloyloxy) ethyl-1,3,5-triazine), liquid-crystalline monomer(4-Methyl phenyl dicyclohexyl ethylene) and functional monomer(methacrylic acid),was pumped into the resulting TRIM monolith. The properties of the MIP monolith were studied by electron microscopic scanning and nitrogen adsorption test, and the chromatographic conditions were systematically investigated. Results showed that the resultant MIP monolith gave raise to good selectivity and imprinting effect even in absence of traditional chemical crosslinking agent. In addition, the liquid-crystalline molecularly imprinted monolith containing immobilised template had better imprinting effect. The results suggested that adding immobilised template is a powerful strategy to increase the effect of molecular imprinting at a low level of crosslinker.