Fluorocarbon liquids suspension polymerisation

Another possible way of overcoming the limitations posed by the presence of water in the suspension polymerisation process is to substitute the continuous water phase with alternative solvents that could still act as dispersing medium for the monomer mixture but better preserve noncovalent interactions in the template-monomer assembly. For example, liquid fluorocarbons are chemically inert and do not affect interactions which are used in noncovalent imprinting. Use of such solvents for the preparation of MIP microbeads has been demonstrated already in 1996 by Mayes and Mosbach [16,17]. A range of MIPs were prepared using Boc-l-phenylalanin as the template, MAA as the functional monomer and different kinds and amounts of crosslinkers and porogenic solvents. The resulting MIP microbeads... 

Liquid fluorocarbon was used as continuous phase by Perez-Moral and Mayes [19] as well. They proposed a new method for rapid synthesis of MIP beads, in that they prepared 36 polymers imprinted for propranolol and morphine with different amounts of EDMA as a cross-linker and different functional monomers (MAA, acrylic acid, hydroxyethyl methacrylate, 4-vinylpyridine) directly in SPE cartridges. The properties of MIP microspheres prepared by this method were very similar in terms of size, morphology and extent of rebinding to microspheres prepared by conventional suspension polymerisation in perfluorocarbons as well as to bulk polymers prepared in the same solvent. The most notable advantages of this method are no waste production (no transfer of beads during washing steps) and possible direct use for a variety of screening, evaluation and optimisation experiments. 

Fig. 1 Scanning electron micrographs of beads prepared by suspension polymerisation in mineral oil (top) or liquid fluorocarbon (bottom) using the microreactor (left) or the conventional approach (right). Reproduced with permission from [23]...

Suspension polymerisation in fluorocarbon liquids (method Ilb in Table 12.1)... 

Fig. 12.3. Electron micrographs of imprinted beads produced by suspension polymerisation of typical EDMA/MAA imprinting mixtures in a liquid fluorocarbon. The porogenic solvents were (a) toluene, (b) chloroform and (c) acetonitrile.

An ideal solution to the problem of finding a universal method for making monodisperse imprinted beads would be a combination of the inertness of fluori-nated liquids with the quality of beads produced by the two-step swelling process. Unfortunately, to date it has not proved possible to make a microemulsion of the organic phase in a liquid fluorocarbon. It might be possible to get some control of particle size, however, by swelling a seed latex with the smallest droplet-size suspension which can be made. Work is in progress to evaluate this possibility. Other methods are available to achieve better particle size control in suspension polymerisation and these should also be evaluated [54]. 

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