Composite Materials in Molecular Imprinting Technology
Abstract: Molecularly imprinted polymers (MIPs) are artificial plastic materials that mimic antibodies or enzymes. Like natural antibodies or enzymes, molecularly imprinted polymers can selectively bind target molecules or can promote catalytic reactions. In contrast to these natural entities, they are robust materials that resist heat, harsh chemicals and the presence of organic solvents. The starting materials are cheap, the preparation is relatively simple and polymer particles have long shelf lives. MIPs constitute therefore promising alternatives to antibodies or enzymes in certain processes. For preparing a MIP, a target molecule along with functional and cross-linking monomers is dissolved in a solvent. The functional monomers interact with the target molecule and form an assembly, which is then frozen in by polymerization. The so obtained polymer block is ground and sieved to yield particles with a desired size. Then the target molecule can be extracted from the polymer particles thereby liberating the specific binding sites. Such traditional, molecularly imprinted polymer particles suffer from a series of disadvantages; the process is quite time consuming and leads to irregular polymer granules that exhibit low capacities, polyclonal binding sites and binding sites that are not well accessible. This thesis gives an overview of various methods with which molecularly imprinted polymers can be prepared that aim at improving the quality of the recognition site. These include new polymerization methods, construction of binding sites on surfaces and preparation of MIPs utilizing heterogeneous systems like imprinting at interfaces. A focus was on the development of a novel approach to molecular imprinting, with the target molecule covalently immobilized on a solid support material. This thesis also describes methods that yield spherical and monodisperse MIP beads, and methods that lead to other well defined physical forms of MIPs, such as composites with pre-formed beads, composites with porous membranes and thin films on flat substrates.
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