Abstract
Molecularly imprinted polymers (MIPs) were fabricated on glass slides with a “sandwich” technique giving ~20 μm thick films. Methanol/water as a solvent, and polyethyleneglycol and polyvinylacetate as solvent modifiers, were used to give a porous morphology, which was studied with scanning electron microscopy and gravimetric analysis. Various MIPs were synthesized through non-covalent imprinting with phenol as the template; itaconic acid, 4-vinylpyridine, and styrene as monomers; ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and pentaerythritol triacrylate (PETA) as cross-linkers. Binding and imprinting properties of the MIPs were evaluated based on phenol adsorption isotherms. Since phenol has only one weakly acidic hydroxyl group and lacks unique structural characteristics necessary for binding specificity, the preparation of selective MIPs was challenging. The recognition of phenol via hydrogen bonding is suppressed in water, while hydrophobic interactions, though promoted, are not specific enough for highly-selective phenol recognition. Nevertheless, the styrene-PETA MIP gave modest imprinting effects, which were higher at lower concentrations (Imprinting Factor (IF) = 1.16 at 0.5 mg·L−1). The isotherm was of a Freundlich type over 0.1–40 mg·L−1 and there was broad cross-reactivity towards other structurally similar phenols. This shows that phenol MIPs or simple adsorbents can be developed based on styrene for hydrophobic binding, and PETA to form a tighter, hydrophilic network.
Highlights
Phenol and other phenolics are water pollutants that orignate from various sources, such as oil extraction and treatment, wood and coal pyrolysis, and industrial organic synthesis [1]
molecularly imprinted polymers (MIPs) can be synthesized by different types of imprinting approaches in a variety of formats [7]
This dependence of wetting and non-specific binding on the cross-linker type can be explained by the higher hydrophilicities of triethylene glycol dimethacrylate (TEGDMA) and pentaerythritol triacrylate (PETA) when compared to ethylene glycol dimethacrylate (EGDMA); TEGDMA has long hydrophilic glycol chain, and PETA possesses a hydroxyl group and lower carbon content due to acrylic moieties instead of methacrylate
Summary
Phenol and other phenolics are water pollutants that orignate from various sources, such as oil extraction and treatment, wood and coal pyrolysis, and industrial organic synthesis [1]. Materials for adsorption of phenol and other phenolics are widely used in wastewater clean-up, solid-phase extraction for chromatographic analysis, and sensors In all these cases, adsorption can be effectively completed with molecularly imprinted polymers (MIPs) [4,5,6]. A non-covalent approach was applied to MIP synthesis because of its simplicity and versatility The core of this approach is formation of a prepolymerization complex between a template and functional monomer (in solvent) through relatively weak interactions: van der Waals, ionic, hydrogen bonding. The prepolymerization solution between two glass surfaces to form a thin continuous polymer film The goal of this project has been to fabricate and study MIP porous films for phenol using different compositions of monomer, solvent and cross-linker. The imprinting effects of these MIPs were evaluated based on analysis of the phenol binding isotherms, and cross-reactivity towards other compounds
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