Monomer-template assemblies stability

Fig. 6-11. Stabilization of monomer template assemblies by thermodynamie eonsiderations.

An important part of the optimization process is the stabilization of the monomer-template assemblies by thermodynamic considerations (Fig. 6-11). The enthalpic and entropic contributions to the association will determine how the association will respond to changes in the polymerization temperature [18]. The change in free volume of interaction will determine how the association will respond to changes in polymerization pressure [82]. Finally, the solvent s interaction with the monomer-template assemblies relative to the free species indicates how well it will stabilize the monomer-template assemblies in solution [16]. Here each system must be optimized individually. Another option is simply to increase the concentration of the monomer or the template. In the former case, a problem is that the crosslinking as well as the potentially nonselective binding will increase simultaneously. In the... 

Some limitations of this molecular imprinting technique are obvious the template must be available in preparative amounts, it must be soluble in the monomer mixture and it must be stable and unreactive under the conditions of the polymerization. The solvent must be chosen considering the stability of the monomer-template assemblies and it should result in the porous structure necessary for rapid kinetics of the template interaction with the binding sites. If these criteria are satisfied, a robust material capable of selectively rebinding the template can be easily prepared and evaluated in a short period of time. 

In the case of electrostatic interactions, lower temperatures of polymerization are known to increase the stability of monomer-template assemblies. Therefore, low temperature initiators are commonly used (for example V-70, V-65 by Wako) or the polymerization is performed using photolabile initiators at lower temperature.29 However, thermally initiated polymerization has a more general scope and may be preferable in certain monomer-template systems. After these initial considerations, initial screening experiments can be designed. 

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