Preparation Of L-tryptophan Imprinted Polymer Microspheres By In Situ Grafting On Surface

Molecularly imprinted polymer (MIP) is a new type of functional polymer materialswith highly specific recognition properties. Recently preparation of surface-imprintedmicrospheres with convenient elution of template, accessibility of surface imprinting sitesand analogous biological recognition has attracted extensive attention. In this paper, themolecular recognition sites were grafted on the surface of porous resin microspheres withL-tryptophan as a template. Surface molecularly imprinted polymer microspheres (SMIPs)with high adsorbing speed and facility in elution were prepared in aqueous media and theadsorption characteristics were analyzed.In this paper, a new method of in situ grafting was proposed for the surfacemodification of acrylate porous polymer microsphere. First the grafting reactive centrewere generated by physically adsorbing initiator on the surface of the porous microspheres.Then the in situ grafting was induced on the surface in aqueous solution. The resultsshowed that a variety of monomer and initiator can achieve the in surface grafting. Thebest grafting rate was achieved when using AM as functional monomer, anhydrous ethanolas solvent and BPO as initiator. Moreover, SEM and FTIR were applied in confirming thepresence of grafted polymer.The template molecule L-trp and the crosslinking MBA were introduced to prepare(trp-SMIPs). The self-assembly of functional monomer and L-tryptophan molecules wasverified by UV spectrometry. Weight change and IR verified the presence of surfacegrafted polymer, The competitive binding experiments were carried out to assess therecognition. The effects of solution pH environment, the molar ratio of template moleculeto functional monomer, dosage of crosslinker and surfactant types on preparation andimprinting behavior were investigated. Additionally, the adsorption of L-trp ontotrp-SMIPs surface was rather fast in the beginning, the adsorption reached equilibriumabout tens of minutes. The correlation coefficients r2show that the adsorption kinetics fitthe pseudo-second model. The isotherm curve of SMIPs was in accordance with Langmuir equation more than Freundlich equation. The maximum adsorption capacity Qmandequilibrium adsorption constant KLwere calculated.Finally, microwave radiation with controlled temperature was employed to promotemicrosphere surface grafting and SMIPs synthesis. The results showed that the effect ofmicrowave radiation can be equals to the traditional water bath, both of which help thepreparation of microspheres with surface grafted polyacrylamide and grafted imprintedpolymer layer. However the microwave radiation can greatly shorten the reaction time,reducing the polymerization from several hours down to tens of minutes, with time-savingand energy-saving advantages.