Molecularly Imprinted Polymer Prepared With Polyhedral Oligomeric Silsesquioxane Through Reversible Addition–fragmentation Chain Transfer Polymerization

Molecular imprinting is a powerful tool for the preparation of artificial receptors to bind a given target molecule.Molecularly imprinted polymers(MIPs)are prepared by mixing imprinting molecule with one or multi-functional monomers to form template-monomer complex,and then copolymerizing functional and cross-linking monomers in the presence of a template.After subsequent removal of the template molecules,the resulting molecularly imprinted polymers(MIPs)can form recognition sites with molecular memory.MIPs thus possess the most important characteristics-specific molecular recognition but larger advantages-low cost,good physical and chemical stabilities.They had been found successfully used in fields where selective binding is needed.Reversible addition–fragmentation chain transfer(RAFT)polymerization is one of the controlled/living radical polymerization(CRP)methods.RAFT polymerization can be applied to various monomers,initiators and polymerization conditions due to its mild reaction conditions.By controlling the concentration of active free radical chain polymerization system,which is always kept at a low level,bimolecular coupling or disproportionation termination reactions will be decreased and the polymer networks will be more homogeneous,thus the selectivity and specificity of the polymer will be better.Polyhedral oligomeric silsesquioxanes(POSS)materials are a class of truly molecularly dispersed nanocomposites,which contain inorganic-organic cagelike architecture with general formula(RSiO1,5)n.Because POSS has multiple reactive functionalities and nanoscale structures,POSS molecules can be easily incorporated into conventional polymers via copolymerisation,grafting or blending.Polyhedral oligomeric silsesquioxane(POSS)was successfully utilized to prepare imprinted polymer through reversible addition–fragmentation chain transfer polymerization(RAFT)for the first time.The imprinted polymer was made with a mixture of RAFT agent,POSS monomer(PSS-(1-Propylmethacrylate)-heptaisobutyl substituted,MA 0702),4-vinylpyridine(4-VP),and ethylene glycol dimethacrylate(EDMA),in the presence of ketoprofen(KET)as template.The influence of polymerization variables on the retention factor and imprinting effect,including the amount of RAFT agent and POSS monomer,the ratio of KET to 4-VP,and the ratio of 4-VP to EDMA,was investigated.The greatest imprinting factor of the imprinted POSS column prepared with RAFT agent was 15.2,about 1.5 times higher than that made in absence of RAFT agent.The comparisons between POSS MIP monoliths made with RAFT agent and without RAFT agent were carried out in terms of permeability,surface morphology and pore size distribution.The optimal MIP was applied to the selective extraction of KET from commercial tablets.The mean recoveries for RAFT-based POSS MIP was 85.2 % for KET with a relative standard deviation(RSD)of less than 2.6 %.