Water sorption isotherms of molecularly imprinted polymers. Relation between water binding and iprodione binding capacity
Résumé
Molecularly imprinted polymers are often used in aqueous medium in order to recognize specifically a target molecule. The molecular recognition is usually based on hydrogen bonding. In this case, water molecule presents a serious competition towards the target molecule. In this study, the water sorption by molecularly imprinted polymers was studied in aqueous medium. The molecularly imprinted polymers were specific for iprodione fungicide and were prepared using a 24 full factorial experimental design. They were synthesized using EGDMA or TRIM as crosslinker, methacrylamide or styrene as functional monomer and using bulk or precipitation polymerization. The water sorption isotherms were established in a range of water activities 0.05–0.90 at 25 °C. The kinetics of water sorption by the polymers were modeled using Peleg's equation. This model shows that polymers having the highest water sorption capacities have high values of imprinting factor. The Guggenheim–Anderson–de Boer isotherm equations were used to fit the equilibrium data and the corresponding parameters were calculated. This model shows that polymers synthesized with EGDMA have higher water sorption capacities than those synthesized with TRIM due to the higher hydrophobicity of the latter. Peleg and Guggenheim–Anderson–de Boer equations satisfactorily modeled the water sorption on the imprinted and non-imprinted polymers. The results obtained from both equations were practically coincident. Principal component analysis was used as a chemometric tool in order to demonstrate that a polymer having a low adsorption energy and a high capacity of water retention could be applied to extract a target molecule from aqueous media.