Computer simulation and synthesis of stimuli-responsive polymer by sol-gel for selective recognition of (4-chloro-2-methylphenoxy)acetic acid

A novel photoresponsive functional monomer bearing a siloxane polymerizable group and azobenzene moieties was synthesized, and then photoresponsive molecularly imprinted sol-gel polymers were successfully fabricated from the synthesized functional monomer, using (4-chloro-2-methylphenoxy)acetic acid (MCPA) as a molecular template. The photoisomerization properties of the functional monomer are retained after incorporation into the rigid three-dimensional crosslinked polymer matrix. The template is then removed from the resulting polymer to generate pores, which are complementary to the template in shape, size and functionality. The substrate affinity of the molecularly imprinted polymer (MIP) receptor sites is photoswitchable. This can be attributed to the photoisomerization of azobenzene chromophores within the MIP receptors, resulting in alteration of their geometry and the spatial arrangement of their binding functionalities. The binding affinity of the imprinted recognition sites was switchable by alternate irradiation with UV and visible light, suggesting that azobenzene groups located inside the binding sites could be used as chemical sensors and the trans-cis isomerization could regulate the affinity for MCPA. To study the hydrogen bond interactions between template molecules and functional monomer, computational molecular modeling was employed. The data indicate that the design of the MIP is rational. (C) 2012 Society of Chemical Industry