L-苹果酸分子印迹聚合物微球的制备及性能评价

以L-苹果酸为模板分子,丙烯酰胺(AA)、乙二醇二甲基丙烯酸酯(EGDMA)分别为功能单体和交联剂,采用沉淀聚合法制备了分子印迹聚合物微球,研究了聚合体系组成对模板聚合物吸附特性的影响。实验表明,以1∶4∶20的物质的量比加入模板分子、AA和EGDMA时,制备的模板聚合物吸附容量高,印迹效果好。通过Scat-chard分析研究了聚合物的选择结合性能,结果表明分子印迹聚合物微球在识别L-苹果酸的过程中存在2类结合位点,而空白印迹聚合物微球只存在1类结合位点。印迹聚合物微球对L-苹果酸和D-苹果酸的手性分离因子α达2.05。     

分子印迹聚合物微球制备方法研究进展

分子印迹聚合物微球具有制备简单、使用方便、分子识别效率高且便于控制粒径大小和功能设计等优点，近年来成为分子印迹技术领域研究的热点之一。对分子印迹聚合物微球的制备方法：溶胀悬浮聚合法、沉淀聚合法、悬浮聚合法和表面聚合法及其最新研究进展作了较为详细的综述。     

分子印迹聚合物微球合成方法研究进展

对近年来发展起来的分子印迹聚合物微球(MIPMs)合成方法的研究进展进行了综述。重点介绍了表面分子印迹聚合物合成法、核-壳型分子印迹聚合物合成法、基于β-环糊精分子印迹聚合物的合成法3种新型MIPMs制备方法。阐述了常用的沉淀聚合法、种子溶胀聚合法、悬浮聚合法合成MIPMs的发展现状。最后对MIPMs的发展趋势提出了展望。     

分子印迹聚合物的吸附行为研究

被吸附分子到达结合位点以及其与印迹位点的结合是影响分子印迹聚合物吸附行为的重要因素。相关文献对后者的研究较多,而前者主要与聚合物的传质特性相关,虽然日益得到重视,由于影响因素较复杂,仍然是分子印迹聚合物研究的一个薄弱环节。因此以两种代表性功能单体化合物—丙烯酰胺和4-乙烯基吡啶为功能单体,木犀草素为模板分子制备了分子印迹聚合物,通过红外光谱(IR)、扫描电子显微镜(SEM)和氮气吸附实验对聚合物的物理性能与静态平衡吸附性能的关系进行研究,旨在阐明功能单体对印迹聚合物微孔结构的影响,并探讨了这些性能与聚合物的吸附性能的关系。     

2,4,6-三硝基甲苯磁性分子印迹聚合物的合成

以2,4,6-三硝基甲苯(TNT)为模板分子、氨丙基三乙氧基硅烷为功能单体、正硅酸乙酯为交联剂,采用溶胶凝胶法成功制备了对TNT具有特异选择识别功能的磁性分子印迹聚合物。合成制备的磁性分子印迹聚合物具有良好的磁响应性,在外加磁场下可实现快速分离。红外光谱(FT-IR)、X射线光电子能谱和扫描电镜结果证实聚合物为核壳结构,磁性粒子由硅烷偶联剂完全包覆,并在其表面形成了一层分子印记聚合物;静态吸附实验结果表明,制备的磁性分子印迹聚合物对模板分子TNT具有良好的吸附能力,其饱和吸附量为77mmol/kg;通过以3,4-二硝基甲苯(DNT),为结构相似物的吸附选择性实验,磁性印迹聚合物对模板分子表现出良好的特异选择性。     

高选择性Pb2+印迹聚合物的制备及吸附性能

以Pb2+为模板分子,以壳聚糖为功能单体,利用分子印迹技术制备了交联壳聚糖分子印迹聚合物,用并原子吸收分光光度计研究其合成、吸附和洗脱等条件对聚合物的吸附性能的影响,并做了选择性实验和在样品回收实验。结果表明:合成的分子印迹聚合物抗酸性提高了,可以重复利用,且保留了对Pb2+良好的吸附性和识别选择性,并具很好的富集效果。     

单一结合位点分子印迹聚合物的合成及性能

采用分子自组装印迹技术在光引发条件下制备了以(S)-布洛芬为模板分子,α-甲基丙烯酸为功能单体的分子印迹聚合物。通过红外对聚合物的结构进行了表征。透射电镜结果表明,交联剂用量对印迹聚合物的形貌特征具有显著的影响。同时结合Scatchard分析研究了印迹聚合物的吸附性能及选择性识别能力,表明印迹聚合物特异性吸附容量为41μmol/g,印迹指数为2.28,对(S)-布洛芬形成单一结合位点,且表现出明显的吸附选择性。     

盐酸二甲双胍磁性分子印迹聚合微球的合成

以盐酸二甲双胍为模板分子、Fe_3O_4为磁核、α-甲基丙烯酸为功能单体、乙二醇二甲基丙烯酸酯为交联剂、偶氮二异丁腈为引发剂,采用表面印迹聚合法成功制备了对盐酸二甲双胍具有特异性识别功能的磁性分子印迹聚合微球。合成的磁性聚合物具有良好的磁响应,在外加磁场下可实现快速磁分离。红外光谱、X射线光电子能谱和扫描电镜结果证实聚合物为核壳结构,磁性粒子由硅烷偶联剂完全包覆,并在其表面形成了一层分子印记聚合物。静态吸附实验结果表明,制备的磁性分子印迹聚合物对模板分子盐酸二甲双胍具有良好的吸附能力,其饱和吸附量为83mmol/kg。以双胍类降糖成分盐酸丁二胍和盐酸苯乙双胍为竞争分子,磁性印迹聚合物对模板分子表现出良好的特异选择性。     

单步溶胀聚合法制备单分散分子印迹聚合物微球:孔结构及其吸附与识别性能

采用单步溶胀聚合法在水溶液中制得了单分散的S-萘普生分子印迹聚合物微球。利用扫描电镜及氮气吸附试验分析了微球的形态及孔结构,并考察了微球的吸附与识别性能。研究结果表明,通过单步溶胀聚合法制得的分子印迹聚合物微球具有较窄的粒径分布（ε〈2．0％）,氯仿及交联剂的用量对微球的表面形态、孔径大小及分布、比表面积等都有明显的影响。Scatchard分析表明分子印迹聚合物微球在识别S-萘普生分子过程中存在两类结合位点,高亲和力的结合位点的离解常数为Kd1=2.13mmol/L,Qmax1=36.46μmolg/g,低亲和力的结合位点的离解常数为Kd2=31．55mmol／L,Qmax2=389．99μmol／g。     

中空结构双模板分子印迹微球的制备及在燃油脱硫中的应用

以Si O2为载体,甲基丙烯酸(MAA)为功能单体,运用蒸馏沉淀法制备出苯并噻吩(BT)、二苯并噻吩(DBT)复合模板分子印迹聚合物,去除载体后得到中空分子印迹聚合物(H-MIP)。利用傅里叶变换红外光谱仪、透射电镜对其进行表征,在模拟汽油环境中测试该印迹聚合物的吸附性能。结果表明,该中空结构的多孔分子印迹聚合物对BT及DBT表现出良好的选择性吸附性能,吸附容量分别为188μmol/g和212μmol/g,同时该产品可在短周期内重复使用。     

Preparation of molecularly imprinted polymers for the detection of aromatic hydrocarbons

In this study, the molecularly imprinted polymers (MIPs) are designed to improve their sensitivity and selectivity for specific aromatic hydrocarbons such as benzene, toluene, and xylene isomers. The MIPs based on methyl acrylate (MA) monomer are prepared using toluene and ethylene glycol dimetacrylate (EGDMA) as a template and a cross linking agent, respectively. The binding sites on the MIPs are characterized by using Fourier transform infrared spectrometry (FT-IR), nitrogen adsorption isotherms, and transmission electron microscopy (TEM). The selective behaviors of the MIPs are evaluated by their adsorption properties on a gravimetric apparatus. It is found that the performance is strongly influenced by the composition ratios of cross-linker, functional monomer, and template molecule. The molecular recognition ability can be assessed on the basis of an imprinting effect. The results indicate that the prepared MIPs can be used for the aromatic hydrocarbon sensor materials with high sensitivity and selectivity.     

Preparation and characterization of molecularly imprinted polymers for the selective separation of 2,4-dichlorophenoxyacetic acid

As a method of preparing ligand-selective cavities in a synthetic polymer matrix, molecular imprinting technique has been attracting significant interest from a large number of areas in chemistry and analytical sciences. In this study, molecularly imprinted polymers (MIPs) were prepared with styrene, 4-vinylpyridine (4-VPy), and divinylbenzene (DVB) for the separation of hazardous 2,4-dichlorophenoxyacetic acid (2,4-D), and the selectivity of MIPs as adsorbed 2,4-D and structurally similar materials was evaluated. The template was removed through the swelling process of toluene/ethanol, and the removal ratio was about 95–99%, respectively. MIPs synthesized in this study had good adsorption selectivity in the presence of other materials, although there was a difference of adsorption quantities (uptake) in the functional monomer (4-VPy contents) and the cross-linker (DVB contents). The results exhibit that the selectivity of MIPs was improved significantly by controlling the cross-linker. We expect that molecular imprinting technique will serve as a novel method for selective separation of specific materials in various fields, especially in the fields of environment and pharmaceutics.     

Design of size-tunable molecularly imprinted polymer for selective adsorption of acetaminophen

Pharmaceutical and personal care products are a broad and diverse group of biologically active compounds which are widely used and unregulated suspected carcinogens. In this study, the fabrication of molecularly imprinting polymer (MIP) particles by precipitation polymerisation were developed to selectively and rapidly capture acetaminophen, a commonly used analgesic and antipyretic drug, by hydrogen and hydrophobic bondings. Methacrylic acid, 3-(trimethoxysilyl) propyl methacrylate and 2, 2′-azobis-isobutyronitrile were utilised as the functional monomer, cross-linker and initiator. Acetonitrile was found to be the optimised porogen to obtain imprinted polymers with surface area and pore size of 447.2 m²/g and 3.35 nm. By adjusting the ratio of cross-linker and functional monomer, the particle size of MIPs changed from 177 to 2782 nm when the ratio increased from 0.43 to 12.8. In addition, the adsorption equilibrium of acetaminophen by MIPs can be reached within the first 30 min because of the surface imprinting characteristics and small particle sizes. In addition, the maximum adsorption capacity of acetaminophen and the adsorption constant, well fitted by Langmuir equation, were 0.35 mg/g and 0.045 L/mg. In addition, the MIPs exhibited the excellent selectivity to acetaminophen. The high surface area and adsorption capacity and excellent selectivity make MIPs an ideal tailor-made green material and can open the door to develop the novel technology for adsorption and removal of pharmaceutical and personal care products in the environment.     

Uniformly sized molecularly imprinted polymer for (S)-nilvadipine. Comparison of chiral recognition ability with HPLC chiral stationary phases based on a protein

Uniformly sized molecularly imprinted polymers (MIPs) for (S)-nilvadipine have been prepared by a multistep swelling and polymerization method using methacrylic acid, 2-(trifluoromethyl)acrylic acid, 2-vinylpyridine, or 4-vinylpyridine (4-VPY) as a functional monomer and ethylene glycol dimethacrylate (EDMA) as a cross-linker. The chiral recognition abilities of the MIPs for nilvadipine and other dihydropyridine calcium antagonists were evaluated using a mixture of sodium phosphate buffer (or water) and acetonitrile or only acetonitrile as the mobile phase. The (S)-nilvadipine-imprinted 4-VPY-co-EDMA polymers gave the highest resolution for nilvadipine among the MIPs prepared. In addition, the enantioseparation of nilvadipine was attained using the (S)-nilvadipine-imprinted EDMA polymers, without use of a functional monomer. 1H NMR and molecular modeling studies suggested a one-to-one hydrogen-bonding-based complex formation of (S)-nilvadipine with 4-VPY in chloroform. These results reveal that the (S)-nilvadipine-imprinted EDMA polymers could recognize the template molecule by its molecular shape, and that in addition to this recognition, hydrophobic and hydrogen-bonding interactions seems to play important roles in the retention and chiral recognition of nilvadipine on the 4-VPY-co-EDMA polymers in hydroorganic mobile phases. By optimizing chromatographic conditions such as column temperature and flow rate, the baseline separation of nilvadipine enantiomers was attained with a short analysis time and with a column efficiency comparable to commercially available chiral stationary phases based on a protein, such as ovomucoid or alpha1-acid glycoprotein.     

Characterization of molecularly imprinted polymers with the Langmuir-Freundlich isotherm

The majority of binding models that have been applied to molecularly imprinted polymers (MIPs) have been homogeneous models. MIPs, on the other hand, are heterogeneous materials containing binding sites with a wide array of binding affinities and selectivities. Demonstrated is that the binding behavior of MIPs can be accurately modeled by the heterogeneous Langmuir-Freundlich (LF) isotherm. The applicability of the LF isotherm to MIPs was demonstrated using five representative MIPs from the literature, including both homogeneous and heterogeneous MIPs. Previously, such comparisons required the use of several different binding models and analyses, including the Langmuir model, the Freundlich model, and numerical approximation techniques. In contrast, the LF model enabled direct comparisons of the binding characteristics of MIPs that have very different underlying distributions and were measured under different conditions. The binding parameters can be calculated directly using the LF fitting coefficients that yield a measure of the total number of binding sites, mean binding affinity, and heterogeneity. Alternatively, solution of the Langmuir adsorption integral for the LF model enabled direct calculation of the corresponding affinity spectrum from the LF fitting coefficients from a simple algebraic expression, yielding a measure of the number of binding sites with respect to association constant Finally, the ability of the LF isotherm to model MIPs suggests that a unimodal heterogeneous distribution is an accurate approximation of the distribution found in homogeneous and heterogeneous MIPs.     

Characterization of the imprint effect and the influence of imprinting conditions on affinity, capacity, and heterogeneity in molecularly imprinted polymers using the Freundlich isotherm-affinity distribution analysis

Molecularly imprinted polymers (MIPs) have been used in a wide range of analytical applications in particular in chromatography and sensing. However, the binding properties in MIPs are typically measured only in a narrow concentration range, which corresponds to only a subset of the sites in MIPs. This limited analytical window and binding site heterogeneity of MIPs leads to inaccuracies and inconsistencies in the estimation of their binding properties. This has hampered the characterization and optimization of MIPs for analytical applications. In this study, the origins of the molecular imprinting effect were studied using the newly developed Freundlich isotherm-affinity distribution (FIAD) analysis. The analysis is able to readily calculate an affinity distribution for MIPs from the limited analytical window. The FIAD analysis also yields an estimate of number, affinity, and heterogeneity for this subset of binding sites. Consistent with previous studies, MIPs were found to have higher capacities than the corresponding nonimprinted polymers (NIPs). Interestingly, MIPs were also found to be more heterogeneous than NIPs. Examination of variables in the imprinting process including temperature, template concentration, and cross-linking percentages further confirmed these trends. Based on these observations, a model for the imprinting effect was developed. The larger population of high-affinity sites in MIPs appears to arise from a broadening of the heterogeneous distribution. This suggests that noncovalent MIPs may be ill-suited for chromatographic applications and other applications that are detrimentally affected by binding site heterogeneity and better suited to applications that are less affected by heterogeneity such as sensing.     

Ultratrace Enrichment of Tyrosine Phosphorylated Peptides on an Imprinted Polymer

Novel molecularly imprinted polymers (MIPs) designed to bind the side chain of phosphotyrosine can be used as artificial receptors for affinity-based enrichment of proteolytic peptides. In comparison with general enrichment methods for phosphorylated peptides such as TiO(2)-based methods, the pTyr-imprinted polymers offered high selectivity for pTyr-containing peptides down to the low fmol level. This suggests MIPs as a new tool for affinity-based proteomics.     

Analyzing the mechanisms of selectivity in biomimetic self-assemblies via IR and NMR spectroscopy of prepolymerization solutions and molecular dynamics simulations

Molecularly imprinted polymers (MIPs) for 2,4-dichlorophenoxyacetic acid were synthesized via a noncovalent approach with 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linker in a methanol/water mixture. Templated polymers synthesized in this self-assembly approach rely on complex formation between the target analyte and functional monomers in porogenic solution prior to radical polymerization. Consequently, the achievable selectivity is governed by the nature and stability of these complexes. The nature of noncovalent interactions responsible for complex formation during imprinting of the template 2,4-dichlorophenoxyacetic acid (2,4-D) with the functional monomer 4-vinylpyridine has been investigated. Fourier transform infrared and 1H NMR spectroscopies provide the fundamental analytical basis for rationalizing the mechanisms of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. Molecular modeling studies in explicit solvent (chloroform and water) corroborate the importance of hydrogen bonding in aprotic solvents and of hydrophobic interactions in protic media in agreement with the experimental spectroscopic investigations of prepolymerization solutions. Furthermore, chromatographic studies of the synthesized MIPs provided insight on the importance of size, shape, and functionality during selective 2,4-D rebinding processes confirming the results obtained during the prepolymerization studies.     

Exploiting β-cyclodextrin as functional monomer in molecular imprinting for achieving recognition in aqueous media

A series of molecularly imprinted polymers (MIPs) for 4,4′-(1,4-phenylenediisopropylidene)bisphenol (BPP) were prepared by using β-cyclodextrin (β-CD) as functional monomer, toluene 2,4-diisocyanate (TDI) or 4,4′-Diphenylmethane diisocyanate (DDI) as the cross-linker. The results of binding experiments showed that the MIPs can bind the template selectively in aqueous media. The binding specificity mechanism of the polymers was investigated in detail. The template molecule is too large and cannot be included in the cavity of one β-CD molecule. The mutual orientation of β-CD molecules in the imprinted polymers is regulated by molecular imprinting, so that they can cooperatively bind the template molecule. It is suggested that the major contribution to the recognition ability of the imprinted polymer was the stereo-shape effect inherent in the MIPs. The study indicated that hydrophobic effects play an important role in the recognition process.     

Thermometric sensing of nitrofurantoin by noncovalently imprinted polymers containing two complementary functional monomers

Molecularly imprinted polymers (MIPs) for nitrofurantoin (NFT) recognition addressing in parallel of two complementary functional groups were created using a noncovalent imprinting approach. Specific tailor-made functional monomers were synthesized: a diaminopyridine derivative as the receptor for the imide residue and three (thio)urea derivatives for the interaction with the nitro group of NFT. A significantly improved binding of NFT to the new MIPs was revealed from the imprinting factor, efficiency of binding, affinity constants and maximum binding number as compared to previously reported MIPs, which addressed either the imide or the nitro residue. Substances possessing only one functionality (either the imide group or nitro group) showed significantly weaker binding to the new imprinted polymers than NFT. However, the compounds lacking both functionalities binds extremely weak to all imprinted polymers. The new imprinted polymers were applied in a flow-through thermistor in organic solvent for the first time. The MIP-thermistor allows the detection of NFT down to a concentration of 5 μM in acetonitrile + 0.2% dimethyl sulfoxide (DMSO). The imprinting factor of 3.91 at 0.1 mM of NFT as obtained by thermistor measurements is well comparable to the value obtained by batch binding experiments.