Environmental Functional Photo-Cross-Linked Hydrogel Bilayer Thin Films from Vanillin

Abstract

A new functional monomer based on vanillin was synthetized and used in the preparation of three different molar concentrations of temperature and pH responsive photo-cross-linker polymers via free radical polymerization with N-isopropylacryamide and malimide photo-cross-linker. Polymers were investigated by 1HNMR, FTIR, UV, gel permeation chromatography (GPC) and differential scanning calorimetery (DSC). The non-responsive copolymers have been synthetized from N,N-dimemthylacrylamide with malimide. Lower critical solution temperatures (T c ) were determined by UV–Vis spectroscopy. Hydrogel bilayer was formed by spin coating of polymer solution of poly(N-isopropylacryamide-Co-malimide-Co-DEAMVA) layer A over gold with adhesion promoter, then cross-linked by UV-irradiation. The swelling properties were determined by surface plasmon resonance with optical waveguides (SPR/OW). The T c of hydrogel was also determined as function of volume degree of swelling or refractive index with temperature at different pH. The next layer was formed by spin coating of polymer solution poly(N,N-dimemthylacrylamid-Co-malimide) layer B over layer A, then cross-linked by UV-irradiation. The swelling properties and T c were determined by SPR/OW in different media. Our target is the formation of biosensor functional gel vessel for biological molecules using aldehyde group. The bilayer functional hydrogels will have an additional feature, in which the target molecule stays safely inside this gel vessel responsively temperature and pH. New acrylate monomer from vanillin has been synthetized with aldehyde and tertiary amine group to achieve both functionality and pH responsive. The copolymerization with NIPAAm and DMIAAm has done forming pH and temperature photo-cross-linked polymers. Hydrogel layer was built first with mono then bilayer and both has characterized by SPR/OW. The effect of non-responsive layer on the responsive one was demonstrated. In future we will use this technique as biosensor hydrogel for vessel to attach and detach biomolecules, further drug-delivery.