Molecular imprint membranes of polyacrylonitrile copolymers with different acrylic acid segments

Poly(acrylonitrile-co-acrylic acid) (P(AN-co-AA)) with different acrylic acid (AA) segments was used to prepare molecular imprint membranes encoding the information of the theophylline (THO) template molecule. The copolymer membranes having 5, 10, 15, 21 and 26 mol% of AA segments were obtained by phase inversion of P(AN-co-AA) in the presence of the template and then the template molecule was extracted for preparation of the imprinted membrane. The binding of THO or structurally analogous caffeine (CAF) was examined by equilibrating the membrane in each substrate aqueous solution. The increase of AA mole fraction in the copolymer causes an increase in the THO binding to the THO-imprinted sites. At higher than 21 mol% AA, the amounts of THO binding to the THO imprinted membrane decrease because of unstable membrane characteristics. Evidence of the interaction between THO and copolymer was shown by infrared spectroscopic analysis of the resultant THO imprinted membrane. Similar experiments were carried out for membranes imprinted using a CAF template. Less effective binding was obtained for each CAF and THO substrate in the CAF imprinted membrane. This supported the suggestion that the copolymer membrane with the AA segments effectively records the shape of THO molecule, since the membrane mainly recognizes the H–N groups of THO through hydrogen bonding between THO and AA segments of the copolymer membrane.