Molecularly imprinted polymers (MIPs) are relatively a new class of selective sorbents. Many applications of these materials have been reported such as stationary phases for HPLC, TLC or SPE, artificial antibodies in binding assays. They have also been successfully used as sensor materials in chemical sensors, due to their high selectivity.

The essence of their preparation is that the target molecule (template) is present in a polymerization mixture where one of the monomers is able to bind to it through a functional group (functional monomer) and another monomer (crosslinker) fixes this complex by creating a polymer network. After polymerization the template is removed leaving behind functional groups in a specific spatial arrangement that can rebind the target analyte.
There are two basic methods for the creation of the template functional monomer complex. One of them is covalent imprinting where the template is covalently bound to the monomer before polymerization and the resulting relatively weak covalent bonds are disrupted when the polymerization is finished. The other, more versatile and simpler method is non-covalent imprinting. In this case the template binds to the monomer in a self-assembly process with van der Waals forces in the pre-polymerization mixture. In this case the resulting polymer usually have lower selectivity, but the MIP preparation and template removal is much easier, and the method is aplicable to a lot more target compounds.

Non-covalently imprinted polymers are usually synthetized by thermally or UV initiated free radical polymerization. The advantage of thermal polymerization lies in its simplicity and low cost, however the high temperature which is demanded by the initiator molecule does not favour template monomer complexation. The temperature of the UV polymerization can be adjusted freely, but it is more complicated and the homogeneous illumination of the polymerization mixture is problematic. The disadvantage of both methods is that an initiator molecule is needed to start the reaction the solubility of which can cause problems.

Ionizing radiation like γ radiation is also capable of initiating polymerization from appropriate monomers. This method has the advantage of generating radicals directly on the monomer, thereby avoiding the use of any initiator. The temperature can be set as wished, even large samples can be homogeneously irradiated.

In our work poly(metacrylamide-co-ethyleneglycol-di- methacrylate) polymers have been imprinted with phenytoin using γ irradiation. The irradiation parameters like irradiation dose, dose rate and polymerization temperature have been optimized. The polymers have been tested in batch adsorption exepriments and compared to thermally polymerized MIPs.

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1. Surface Imprinted Micro- and Nanorod Polymers with Magnetic Cores for Protein Recognition