Influence of vanillin acrylate and 4-acetylphenyl acrylate hydrophobic functional monomers on phase separation of N-isopropylacrylamide environmental terpolymer: fabrication and characterization

In the present study, we synthesized new functional hydrophobic acrylate monomers. The first monomer was based on 4-acetylacetophenone, and the other one was based on vanillin as a renewable resource. The starting material was reacted with acryloyl chloride for the formation of 4-acetylphenyl acrylate (APA) and 4-formyl-2-methoxyphenylacrylate (vanillin acrylate) or (VA), respectively. The chemical structures were deduced by ¹H NMR, 13C NMR, and FTIR. The effect of these monomers on the transition temperature or lower critical solution temperature of thermo-responsive N-isopropylacrylamide was achieved by the free radical polymerization of three different molar concentrations of both APA and VA with NIPAAm in solution and using 2,2′azobis(isobutyronitrile) (AIBN) as an initiator. The terpolymers were chemically evaluated. They have been also investigated by gel permission chromatography (GPC) for molecular weight and molecular weight distribution; the glass temperatures were determined by differential scanning calorimetry DSC; X-ray diffraction (XRD) was used for the extent of crystallinity; scanning electron microscopy was used (SEM) for surface morphology. The phase separation and lower critical solution temperature T_c were measured using two methods: UV–Vis spectroscopy for turbidity measurements and micro-DSC of the polymer solution. In the future, we will use these polymers in the bio-separation process and the formation of a responsive hydrogel.