Fabrication of ordered microporous styrene‐acrylonitrile copolymer blend imprinted membranes for selective adsorption of phenol from salicylic acid using breath figure method

Highly selective, ordered microporous molecularly imprinted membranes (MIMs) for phenol were synthesized by breath figure (BF) method using styrene‐acrylonitrile copolymer (SAN) as the membrane matrix and molecularly imprinted polymer nanoparticles (nano‐MIPs) as the imprinted nanoparticles. The nano‐MIPs were synthesized by oil‐in‐water emulsion polymerization using 4‐vinyl pyridine (4‐VP), methyl methacrylate (MMA) or cinnamic acid (CA) as the functional monomer, respectively. The prepared nano‐MIPs were characterized by transmission electron microscope (TEM) and Raman, whereas MIMs were characterized by SEM, membrane flux, and selective adsorption experiments. Morphological analysis exhibited that the addition of nano‐MIPs improved the formation of ordered and well‐defined porous membrane morphology. Compared with MMA‐MIM and CA‐MIM, the 4‐VP‐MIM exhibited higher membrane flux, adsorption capacity, and stronger selective binding for phenol as well as excellent permeation selectivity for phenol. Moreover, the selective effect of 4‐VP‐MIM on phenol was strongly affected by the amount of 4‐VP imprinted nanoparticles (nano‐4‐VP‐MIPs). The experimental data revealed that the 4‐VP‐MIM containing 2.0 wt % of nano‐4‐VP‐MIPs exhibited the highest separation selectivity for the template phenol, whose selectivity coefficients for phenol relative to salicylic acid (SA) and p‐hydroxybenzoic acid (p‐HB) were 5.6770 and 5.5433, respectively, which was close to the predicted selectivity coefficient value. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42350.     

Preparation of water‐compatible molecularly imprinted polymers for caffeine with a novel ionic liquid as a functional monomer

Water‐compatible molecularly imprinted polymers (MIPs) for caffeine were synthesized in aqueous medium with a new functional monomer, 1‐(α‐methyl acrylate)‐3‐methylimidazolium bromide (1‐MA‐3MI‐Br), which had π–π and hydrogen‐bonding interactions. Caffeine‐imprinted polymers were prepared in suspension polymerization with 1‐MA‐3MI‐Br and methacrylic acid (MAA), which only had hydrogen bonding, as a functional monomer. For the specific binding characteristics of the new functional monomer 1‐MA‐3MI‐Br, the adsorption capacity and relative separation factor (β) of MIPs for caffeine were significantly enhanced. The maximum adsorption capacities of 1‐MA‐3MI‐Br–MIP and MAA–MIP imprinted microspheres for caffeine were 53.80 and 28.90 μmol/g, respectively. Moreover, the relative separation factors were measured by comparison of the separation characteristics under competitive adsorption conditions. The results showed that the β of MAA–MIP for caffeine relative to theophylline was only 1.65; this showed a very poor recognition selectivity for caffeine, but β of 1‐MA‐3MI‐Br–MIP for caffeine with respect to theophylline was remarkably enhanced to 3.19; this showed an excellent recognition selectivity and binding affinity toward caffeine molecules in an aqueous environment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and evaluation of uniformly sized carbamazepine-imprinted microspheres and nanospheres prepared with different mole ratios of methacrylic acid to methyl methacrylate for analytical and biomedical applications

In this work, we initiated to study new synthetic conditions to obtain uniformly sized molecularly imprinted polymers (MIPs) in the micrometer to nanometer range, using carbamazepine (CBZ) as a model template. The MIPs were successfully prepared by precipitation polymerization using methacrylic acid (MAA) and methyl methacrylate (MMA) as functional monomers at different mole ratios. The effect of MAA-to-MMA mole ratios on the morphology, binding, recognition, and release behaviors of the final particles were studied, and the adjusting possibility of these properties was also obtained. The produced polymers were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry, and their morphology was precisely examined by scanning electron microscopy and photon correlation spectroscopy. We obtained very uniform imprinted nanospheres and microspheres with diameter in the range of 120 nm to 1.74 μm under various conditions. Among the MIP nanospheres and microspheres prepared, the MIPs using MAA-to-MMA mole ratio of 1 : 2 showed nanospheres with the lower polydispersity index (0.004) and the highest selectivity factor (10.4), which is defined as the binding ratio of CBZ and oxcarbazepine as template analog. Results from binding experiments proved that MIPs exhibit specific affinity to CBZ in contrast to control polymers, and this performance was affected by pH and concentration of the loading solution. Moreover, release experiments showed the controlled release of CBZ in long-time period. The 50% of loaded CBZ was released from the imprinted nanospheres within the first 30 h, whereas another 50% was released in the following 160 h. The release kinetics of CBZ from the MIPs highly affected with the properties of particles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and Characterization of Molecularly Imprinted Polymer Membrane for the Removal of 2,4-Dinitrophenol

Molecularly imprinted polymers (MIPs) were prepared by bulk polymerization in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide, as the template, functional monomer, cross-linker, and initiator, respectively. The MIP membrane was prepared by hybridization of MIP particles with cellulose acetate (CA) and polystyrene (PS) after being ground and sieved. The prepared MIP membrane was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters studied for the removal of 2,4-dinitrophenol included the effect of pH, sorption kinetics, and the selectivity of the MIP membrane. Maximum sorption of 2,4-nitrophenol by the fabricated CA membrane with MIP (CA-MIP) and the PS membrane with MIP (PS-MIP) was observed at pH 7.0 and pH 5.0, respectively. The sorption of 2,4-dinitrophenol by CA-MIP and PS-MIP followed a pseudo–second-order kinetic model. For a selectivity study, 2,4-dichlorophenol, 3-chlorophenol, and phenol were selected as potential interferences. The sorption capability of CA-MIP and PS-MIP towards 2,4-dinitrophenol was observed to be higher than that of 2,4-dichlorophenol, 3-chlorophenol, or phenol.     

甲基对硫磷分子印迹聚合物制备中溶剂和功能单体的影响

为了有效的分离富集水样中的有机磷农药,以甲基对硫磷为模板、二甲基丙烯酸乙二酯为交联剂,采用传统方法制备了甲基对硫磷分子印迹聚合物(MIPs).考察了三种溶剂和三种功能单体及其用量对MIPs吸附性能的影响.结果表明,以氯仿为溶剂制得的MIP特异性最强,溶剂用量对MIPs比表面积和溶胀比的影响显著.氯仿用量为35 mL时MIP性能最理想;~1H-NMR研究显示,4-乙烯基吡啶(4VP)与模板分子通过π-π堆积作用形成稳定的复合物,按4VP与模板分子摩尔比4:1制得的MIP特异性和亲和性较理想.测定了该MIP的吸附等温线,利用Langmuir等温式分析结果,得出其饱和吸附量为625.5 μmol·g~(-1),明显高于非印迹聚合物的饱和吸附量285.7 μmol·g~(-1).利用该MIP对模拟海水样品进行研究,结果显示,MIP对不同有机磷农药的吸附能力表现出一定的差异.通过进一步优化,提高MIPs的选择性,该材料有望用于水样中甲基对硫磷的分离富集和分析.     

Synthesis and Evaluation of Uniformly Sized Synephrine-Imprinted Microparticles Prepared by Precipitation Polymerization

Uniformly sized synephrine molecularly imprinted polymer (MIP) microparticles were prepared via precipitation polymerization. The presence of the template, the amount of monomer, crosslinker, and porogenic solvent could affect the size distribution and morphology of the polymers. The pseudo-second-order kinetic model could provide a better correlation for the adsorption than the pseudo-first-order model. The intraparticle diffusion study showed that the sorption involved intraparticle diffusion, but that was not the only rate-controlling step. The equilibrium data better fit the Freundlich model than the Langmuir model. The Scatchard plot of MIPs revealed MIPs had two groups of sites with different affinities. Subsequent recognition selectivity experiments demonstrated preferential structural selectivity for synephrine with respect to other structurally similar compounds (i.e., octopamine and tyramine). Compared with the bulk MIP of SYN, the SYN MIP microparticles in this work had higher adsorption selectivity and capacity due to their smaller particle sizes; moreover, the precipitation polymerization was time-saving due to not using a crash-and-sieve process.     

沉淀聚合法制备磺胺二甲嘧啶分子印迹聚合物

以磺胺二甲嘧啶为模板分子,采用沉淀聚合法制备了分子印迹聚合物,并对其选择性和吸附性能进行了研究.等温静态平衡实验结果表明,该印迹聚合物与相应的空白聚合物相比具有高的选择性和亲和性;Scatchard模型分析结果表明,该印迹聚合物对印迹分子存在一种均匀的结合位点,最大表观结合量为31.866 mg/g.     

Exploiting β-Cyclodextrin in Molecular Imprinting for Achieving Recognition of Benzylparaben in Aqueous Media

The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting the –OH group of MAA and one of the primary –OH groups of β-CD. This monomer comprised of triple interactions that included an inclusion complex, π–π interaction, and hydrogen bonding. To demonstrate β-CD performance in MIPs, two MIPs were prepared; molecularly imprinted polymer-methacrylic acid functionalized β-cyclodextrin, MIP(MAA-β-CD), and molecularly imprinted polymer-methacrylic acid, MIP(MAA); both prepared by a reversible addition fragmentation chain transfer polymerization (RAFT) in the bulk polymerization process. Both MIPs were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Brunauer-Emmett-Teller (BET). The presence of β-CD not only influenced the morphological structure, it also affected the specific surface area, average pore diameter, and total pore volume of the MIP. The rebinding of the imprinting effect was evaluated in binding experiments, which proved that the β-CD contributed significantly to the enhancement of the recognition affinity and selective adsorption of the MIP.     

D-对羟基苯甘氨酸分子印迹聚合物的制备及分子识别能力

以D-对羟基苯甘氨酸（D-HPG）为模板分子,以丙烯酰胺（AM）和α-甲基丙烯酸（MAA）为功能单体,乙二醇二甲基丙烯酸酯为交联剂,合成了D-HPG分子印迹聚合物,并测定其对D-HPG的识别能力。静态吸附实验表明,以MAA为功能单体制备的分子印迹聚合物具有更强的分子识别能力,其饱和吸附量达43.9 μmol•g^-1,印迹因子α为3.6。分子力学计算表明,MAA与D-HPG形成复合物的结合能较大,且MAA在乙醇和水中的溶剂化能较小,因此与AM比较,MAA和模板分子D-HPG在乙醇和水中能形成更加稳定的复合物。紫外光谱分析表明,MAA与D-HPG之间的结合力比AM与D-HPG之间的结合力要强,与分子力学计算以及静态吸附实验得到的结果相一致。     

Imprinted β‐cyclodextrin polymers using naringin as template

The objective of this study was to identify a kind of molecular imprinting polymer (MIP) which was suitable for recognizing naringin (NG) in aqueous medium. Based on two crosslinkers (hexamethylene diisocyanate and epichlorohydrin) and two polymerization methods (solution polymerization and emulsion polymerization), four non‐covalent naringin‐β‐cyclodextrine (NG‐β‐CD) imprinted polymers were prepared by using β‐CD as a functional monomer and NG as a template molecule. The binding property and selectivity were evaluated by equilibrium binding experiments. These demonstrated that all the sites in the MIPs show good selective binding ability for NG from naringin dihydrochalcone, a structurally similar molecule. Of the four MIPs, rod‐like 3# MIP which was prepared by emulsion polymerization using hexamethylene diisocyanate as crosslinker exhibited the highest selectivity, its imprinting factor α being 1.53. Scatchard analysis of 3# MIP suggests that there are two classes of binding sites during the MIP's recognition of NG. Additionally, the 3# MIP could be used at least five times without any loss in sorption capacity. Copyright © 2011 Society of Chemical Industry     

Application of Molecularly Imprinted Polymers in Plant Natural Products: Current Progress and Future Perspectives

Plants, as a large and complex system, are rich in a variety of natural bioactive constituents. It is crucial to enrich, isolate, purify and detect these natural products. Molecularly imprinted polymers (MIPs) are a class of polymers prepared by molecularly imprinted technology (MIT) that have specific recognition sites and are complementary to templates in shape, size, and binding groups. The synthesis and polymerization mechanism of MIPs are introduced. A variety of preparation methods for MIPs have been developed. MIPs can be classified into three types: non-covalent molecularly imprinted, covalent molecularly imprinted, and semi-covalent molecularly imprinted. MIPs usually consists of five parts: template, functional monomer, cross-linker, initiator, and solvent/reagent. With the advantages of high-specificity binding ability, MIPs have shown excellent efficacy in the separation, enrichment, and purification of plant active products, such as flavonoids, polyphenols, terpenoids, and other components, especially as specific adsorbent materials. Due to the high selectivity to target the analytes, MIPs have also been used as sensors to detect the bioactive constituents in plants. Undeniably, MIPs still face undeniable limitations in the application of plant natural products. The development of MIPs with high selectivity, strong affinity, cost-effectiveness, sensitivity, and environmental friendliness are valuable and promising.     

Preparation and evaluation of a molecularly imprinted polymer for tolazoline

A uniformly sized molecularly imprinted polymer for the peripheral vasodilator drug tolazoline (T‐MIP) was prepared, and a nonimprinted polymer (NIP) was also synthesized in the same way but in the absence of the template. The T‐MIP was prepared with methylacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinker by a multistep swelling and polymerization method. These imprinted materials were characterized by scanning electron microscopy, nitrogen adsorption, and static adsorption experiments. Binding studies were also performed to evaluate the uptake of T‐MIP and NIP with the results that T‐MIP had a significantly higher binding capacity for tolazoline (T) than did NIP. The maximum static adsorption capacities of T‐MIP and NIP for T were 78.9 and 38.8 μmol/g, respectively. The T‐MIPs and NIPs were used as stationary phases of solid‐phase extraction (SPE), and a relative selectivity coefficient (k′) value of 5.21 was obtained, which showed that the T‐MIP sorbent had higher selectivity than the NIP sorbent. The method was applied to the determination of T in urine samples. The prepared polymer sorbent showed promise for SPE for gas chromatography determination of T in urine samples. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Molecular imprinted solid‐phase extraction of huperzine A from Huperzia Serrata

On the basis of the non‐covalent interaction between template and monomer, porous molecularly imprinted polymers (MIPs) were synthesized by a thermal‐initiated polymerization method using huperzine A as template, acrylamide, or methacrylic acid as function monomer, ethylene glycol dimethacrylate as cross‐linking agent. The interaction between template and functional monomers was studied by UV spectrophotometry, which showed a formation of huperzine A‐monomer complexes with stoichiometric ratio of 1 : 2 in the pre‐polymerized systems. The resultant MIP particles were tested in the equilibrium binding experiment to analyze their adsorption ability to huperzine A, and were characterized by Fourier Transform Infrared (FTIR) study. The recognition properties of MIP were estimated in solid‐phase extraction by selecting four compounds (isolated from the Chinese herb Huperzia serrata) as substrates, and were compared with and prior to those of the NIP. High affinity and adsorption of MIP1 which was prepared in chloroform with huperzine A as imprinted molecule, and acrylamide (AM) as functional monomer, made an attractive application of MIP1 in separation processes. In final, using MIP1 solid‐phase extraction micro‐column, huperzine A was enriched and separated from the real extraction sample of Huperzia serrata. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of the artemisinin‐imprinting polymers on silica surface and its adsorption behavior in supercritical CO2 fluid

Molecular imprinting polymers (MIPs) for artemisinin were prepared by using 3‐aminopropyltriethoxysilane and calix[4]arene bonded on silica particle surface as the functional monomers, tetraethoxysilicane as cross‐linker, and artemisinin as template. The MIPs were characterized by Fourier Transform Infrared Spectroscope and SEM. Their adsorption capacities were evaluated by static adsorption experiments. The MIPs showed high adsorption capacity and good selectivity for artemisinin. The maximum adsorption capacity of MIPs for artemisinin was 40.0 mg/g. The imprinting factor and the selective factor of the artemisinin‐imprinting polymers was 2.0 and 1.5, respectively. The imprinted film coating onto the silica surface showed a fast kinetics for recognizing and binding templates. Especially, mass transfer reaches the equilibrium within 3.5 h and the adsorption capacity of MIPs for artemisinin reached 120.0 mg/g in supercritical CO₂ fluid. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

以b-环糊精、2-羟丙基-b-环糊精和4-乙烯吡啶为功能单体制备氟比洛芬分子印迹聚合物及其吸附特征

以b-环糊精(β-CD)、2-羟丙基-β-环糊精(HP-β-CD)和4-乙烯吡啶(4-VP)为功能单体,以氟比洛芬为模板分子,以环氧氯丙烷和乙二醇二甲基丙烯酸酯为交联剂,采用本体聚合法制备分子印迹聚合物(MIPs),对氟比洛芬与功能单体的相互作用和MIPs的结构进行了表征,比较了3种MIPs对氟比洛芬的吸附性能. 结果表明,β-CD, HP-β-CD和4-VP与氟比洛芬之间以较强的相互作用形成复合物,通过交联、聚合形成聚合物,以HP-β-CD作功能单体所得聚合物印迹效果最佳,具有较强的特异性吸附能力,印迹因子和特异性吸附率分别为1.79和38.92%,分子印迹机制是β-CD的锥筒包结作用和羟丙基的亲和作用形成印迹空穴.     

Grafting of molecularly imprinted polymers from the surface of Fe3O4 nanoparticles containing double bond via suspension polymerization in aqueous environment: A selective sorbent for theophylline

Molecularly imprinted polymers (MIPs) were grafted from the surface of Fe₃O₄ nanoparticles containing double bond via suspension polymerization in aqueous environment, and the leakage of Fe₃O₄ nanoparticles from MIPs was overcome in this study. The effect of different cross‐linker on adsorption capacity of the resultant magnetic MIPs was investigated using pure trimethylolpropane trimethacrylate (TRIM) or the mixture of TRIM and divinylbenzene (DVB) as cross‐linker. Both magnetic MIPs exhibited higher adsorption capacity for the template theophylline than the corresponding non‐imprinted polymer, and Freundlich model fitted reasonably well for theophylline adsorption on both magnetic MIPs. In addition, both magnetic MIPs exhibited good recognition properties for the template theophylline versus caffeine, and the selectivity of magnetic MIPs using pure TRIM as cross‐linker (mag‐MIP‐TRIM) was much higher than those using the mixture of TRIM and DVB as cross‐linker (mag‐MIP‐TRIM and DVB). The adsorption dynamics of theophylline on both magnetic MIPs fitted well with the first‐order kinetic model, but the adsorption equilibrium on mag‐MIP‐TRIM and DVB reached faster than that on mag‐MIP‐TRIM. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of polymerisation methods on the adsorption capacity of HEMA based molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) are generally synthesised either by thermal initiation or by photo polymerisation methods. Recently we used a gamma irradiation method for the preparation of MIPs. In this communication we compare three different methods for the synthesis of 2-hydroxy ethyl methacrylate (HEMA) based MIP imprinted for hydrocortisone in terms of its capacity to adsorb the print molecule. Our results show that MIP prepared by the gamma irradiation method has a better adsorption capacity than the thermally initiated polymer. It is interesting to note that its adsorption capacity is comparable or marginally better than the photo polymerised MIP.     

Highly selective removal of 2,4-dinitrophenol by a surface imprinted sol–gel polymer

In this work, 2,4-dinitrophenol (2,4-DNP), a new molecularly imprinted polymer (MIP) with excellent performance was synthesized in ethanol by the sol–gel method using 3-aminopropyltriethoxysilane as functional monomer on the surface of silica particles. The structure and morphology of MIP were characterized via scanning electron microscopy, nitrogen adsorption–desorption analysis, infrared spectra, and thermogravimetry analysis. Results demonstrated that MIP had excellent selectivity toward the template molecule (2,4-DNP) with an imprinting factor of 9.55 and a maximum static adsorption capacity of 114.7 mg g⁻¹. Data obtained from the adsorption isotherm of 2,4-DNP were fitted well with the Freundlich isotherm model, and the adsorption process can be described by the pseudo-second-order model. The investigation of adsorption mechanism revealed that the specific recognition process of MIP toward 2,4-DNP was dominated by the hydrogen bond and molecular structure. By employing as a sorbent, the as-prepared MIP was applied to recognize and remove 2,4-DNP in poster paper, nonwoven fabric and brown curtain with recoveries in the range from 85.74 to 100.00%. However, the MIP can effectively remove 2,4-DNP after five cycles.     

Cyclodextrin‐based molecularly imprinted polymers for the efficient recognition of pyrethroids in aqueous media

Recent years have witnessed growing applications of the molecular imprinting technique for the detection of pesticide residues in environmental and food samples. In this study, molecularly imprinted polymers (MIPs) for pyrethroids, a class of popular insecticides, were synthesized by the crosslinking of β‐cyclodextrin (β‐CD) with 1,6‐hexamethylene diisocyanate (HMDI) or toluene‐2,4‐diisocyanate (TDI) in dimethyl sulfoxide, with lambda‐cyhalothrin (LCT) as a model template. Equilibrium batch‐rebinding tests were operated in different aqueous solutions. The results indicate that MIP prepared with TDI (MIP–TDI) possessed a much greater binding activity to LCT than MIP based on HMDI (MIP–HMDI), and MIP–TDI displayed a remarkably specific binding to LCT (with an imprinting factor of around 3) in an acetonitrile/water (4:7 v/v) mixture. The adsorption of LCT by MIP–TDI reached equilibrium after 3 h; this demonstrated comparatively rapid adsorption kinetics. Also, MIP–TDI could be regenerated eight times at least; this implied that the robust β‐CD polymer has the potential for practical applications. Furthermore, a cross‐selectivity study indicated that the high adsorption of LCT and its analogues by MIP–TDI in aqueous media must have been ascribed to the cooperative effects of CD inclusion interaction and stereoshape memory. This study paved the way for the use of β‐CD as a functional monomer for preparing smart artificial receptors for the efficient recognition of pyrethroids under aqueous conditions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013