Abstract: In this paper, melamine (MAM) was chosen as the template molecule and acrylamide (AM), methacrylic acid (MAA), N, N'-methylenebisacrylamide (MBA), itaconic acid (IA) were as the function monomers, the ethylene glycol dimethacrylate (EGDMA), trimethacrylate (TRIM), and divinylbenzene (DVB) were as the cross-linking agents, respectively. Long-range correction method of quantum chemistry density functional theory was used to simulate and discuss the bonding site, the number of hydrogen bonds, imprinted ratio of the stable complex, and the reaction mechanism. The optimizations of function monomers and the cross-linking agents were according to the bond energy (Δ E). The nature of the imprinting effect was also studied by the atoms in molecules (AIM) theory. The results indicate that MAM and the four monomers have interaction to form imprinted polymers via the hydrogen bonds, and the molar ratio was 1:6. The MIPs synthesized using IA as monomer owns the lowest bond energy, and the complex configuration is the most stable. The DVB as cross-linking agent with the highest binding energy in comparison with the TRIM and EGDMA is the best one for MAM-MIPs. In addition, the MAM-MIPs were prepared by precipitation polymerization to study the adsorption capacity characteristics. The results show that the MAM-MIPs (molar ratio = 1:6) synthesized with IA as monomer and DVB as cross-linking agent have the best binding capacity. The average diameter of MAM-MIPs is 195 nm. The analysis of the Scatchard plot reveals that the binding sites of MAM-MIPs to MAM are equal class under the studied concentration range, the apparent maximum adsorption quantity (Qmax) is 20.79 mg/g, the dissociation constant (Kd) is 58.82 mg/L. The adsorption quantity of MIPs to MAM is obviously higher than that of cyromazine (CYR), cyanuric acid (CYA), and trithiocyanuric (TRI) in milk, which shows better specific absorption capacity. The studies can provide theoretical and experimental basis for screen of the functional monomer, the imprinting ratio, and cross-linking agent for the preparation of MAM-MIPs.
Template and target information: melamine, MAM
Author keywords: Melamine, Molecularly imprinted polymers, functional monomer, Cross linking agent, binding capacity