Effect of functional monomers and porogens on morphology,structure and recognition properties of 2-(4-methoxyphenyl)ethylamine imprinted polymers

2-(4-Methoxyphenyl)ethylamine imprinted polymers were obtained from seven functional monomers in four porogens, and their properties were tested. Binding experiments revealed the highest selectivity towards a template for the polymer prepared from methacrylic acid in toluene (MIP1). The binding capacities and the imprinting factors were different for the stationary and the dynamic evaluation procedures. For MIP1, the binding capacities were 6.991 ± 0.081 or 18.247 ± 0.005 μmol g^? 1, and the imprinting factors were 1.97 or 3.84, for stationary and dynamic procedures, respectively. The Scatchard analysis of MIP1 showed two classes of binding sites with values of the dissociation constants K_d equal to 16.2 and 192 μmol L^? 1. Composition of polymers was supported by ¹³C CP/MAS NMR, FTIR and SEM-EDS analyses. The binding abilities of MIP1 towards the structurally related compounds showed that the ethylamine group together with steric effects governed the recognition mechanism. Finally, the high affinity of MIP1 towards dopamine or serotonin, but low towards norepinephrine and epinephrine was demonstrated.     

Impact of functional monomers,cross-linkers and porogens on morphology and recognition properties of 2-(3,4-dimethoxyphenyl)ethylamine imprinted polymers

The main objective of this paper was to examined the impact of synthetic reagents on morphology and recognition properties of 2-(3,4-dimethoxyphenyl)ethylamine imprinted polymers. The effect of nine different functional monomers, five porogens and four cross-linkers on the binding capacity of particles was analyzed. The results revealed that the highest imprinting factor (1.81) showed the polymer obtained from methacrylic acid and ethylene glycol dimethacrylate in toluene. The binding capacities of imprinted (MIP1) and non-imprinted (NIP1) materials were 135.3 ± 9.8 and 74.8 ± 7.8 μmol g^? 1, respectively. The specific surface areas were 55.05 ± 3.89 for MIP1 and 38.72 ± 2.40 m² g^? 1 for NIP1. The SEM analysis confirmed that the surface of MIP1 is rougher and denser than NIP1. Structural analysis supported by ¹³C CP/MAS NMR spectra was also performed. The binding abilities of homoveratrylamine and eight structurally related compounds to MIP1 showed that strong interactions between carboxylic group in the polymer and amine group in the analyte together with its molecular volume govern the recognition mechanism.     

Molecularly imprinted polymers based on iodinated monomers for selective room-temperature phosphorescence optosensing of fluoranthene in water

Aiming at enhancing the advantages of traditional molecularly imprinted polymers (MIPs) for chemical sensing, a new MIP design approach introducing an internal heavy atom in their polymeric structure is described. Based on the heavy-atom effect, the novel polymer allows one to perform room-temperature phosphorescence (RTP) transduction of the analyte. The synergic combination of a tailor-made MIP recognition with a selective RTP detection is a novel concept for optosensing devices which is assessed here for simple and highly selective determination of trace amounts of fluoranthene in water. The noncovalent MIP was synthesized using the laboratory-synthesized tetraiodobisphenol A as one of the polymeric precursors and fluoranthene as template. In the presence of an oxygen scavenger, the iodide included in the polymeric structure induced efficient RTP emission from the analyte, once recognized by the MIP. The developed optosensing system has demonstrated a high specificity for fluoranthene against other polycyclic aromatic hydrocarbons. Detection limit for the target molecule was 35 ng/L (5-mL sample injections), and the linear range extended above 100 microg/L of the analyte. The polymer can be easily regenerated for subsequent sample injections (at least up to 450 cycles) with acetonitrile. The synthesized sensing material showed good stability for at least 6 months after preparation. The feasibility of monitoring fluoranthene in real samples was successfully evaluated through the analysis of five spiked river water samples.     

Computational approach to the rational design of molecularly imprinted polymers for voltammetric sensing of homovanillic acid

A methodology based on density functional theory calculations for the design of molecularly imprinted polymers (MIPs) is described. The method allows the rational choice of the most suitable monomer and polymerization solvent among a set of chemicals traditionally used in MIP formulations for the molecular imprinting of a given template. It is based on the comparison of the stabilization energies of the prepolymerization adducts between the template and different functional monomers. The effect of the polymerization solvent is included using the polarizable continuum model. A voltammetric sensor for homovanillic acid was constructed using different MIPs as recognition element, confirming that the solvent (toluene) and functional monomer (methacrylic acid) selected according to the theoretical predictions lead to the most efficient molecular recognition sensing phase. With the voltammetric sensor prepared using the MIP designed according to the theoretical predictions, a linear response for concentrations of homovanillic acid between 5 x 10(-8) and 1 x 10(-5) M can be obtained. The limit of detection is 7 x 10(-9) M. The selectivity obtained for homovanillic acid over other structurally related compounds buttresses the validity of this strategy of design.     

New materials which respond to visible light: functional polymers containing zirconium

Photoresponsive polymers which change their magnetic properties when illuminated by visible light have been found. n-Butyl zirconate was polymerized in tetrahydrofuran and other solvents. The polymer, when illuminated, changes its conformation and a new spin-nuclear interaction in the electron spin resonance spectrum is observed. These polymers, when 1 wt% Pt was added, exhibited photocatalytic activities and photolysed a 1:1 methanol-H₂O mixture and a 0.24 M Na₂S aqueous solution, using visible light of wavelength 480 to 730 nm.     

Viscoelasticity and fracture toughness of blended epoxy resins containing two monomers with different molecular weights

In the present work, we investigated the thermo-viscoelasticity and fracture toughness of various cured blends of two epoxy monomers with different molecular weights: 380 (Epikote 828) and 900 (Epikote 1001). The blended resins were easily prepared, and miscibility (no phase separation) in the blended resins was expected. The composition of the blended epoxy resins ranged from 0 to 100% by weight of the Epikote 1001. The measured damping factor and dynamic loss modulus in the glass-transition confirmed that each blended resin had a single phase, i.e., they were miscible. The fracture toughness at room temperature increased modestly with the Epikote 1001 content over the whole range (0–100 wt%). We found that below the glass-transition temperature, the macromolecular modifications enabled tailoring of the fracture toughness while maintaining the glassy bending modulus and with little change in the glass-transition temperature.     

分子印迹聚合物在分离领域的应用

分子印迹技术是近年来集高分子合成、分子设计、分子识别、仿生生物工程等众多学科优势发展起来的一种应用广泛的新型技术.阐述了分子印迹方法的基本原理,介绍了分子印迹聚合物在分离领域的应用.综述了该技术的研究现状,并展望了其发展趋势.     

分子印迹传感器的研究进展

分子印迹传感器具有灵敏度高、选择性好、价格低廉等优点,因此,受到许多研究者广泛的关注和深入的研究。文章介绍了分子印迹聚合物的主要制备方法,分子印迹聚合物和分子印迹传感器的识别机理,综述了分子印迹技术在光学传感器、电化学传感器方面的应用,并展望了分子印迹传感器未来的研究方向。     

Optical detection of chloramphenicol using molecularly imprinted polymers

A practical optical sensing system for the determination of chloramphenicol (CAP), utilizing molecularly imprinted polymers (MIPs) and HPLC, has been developed. The method is based on competitive displacement of a chloramphenicol-methyl red (CAP-MR) dye conjugate from specific binding cavities in an imprinted polymer by the analyte. The best of these polymers was obtained using (diethylamino)ethyl methacrylate as functional monomer at a monomer:template ratio of 2:1. HPLC with a mobile phase containing CAP-MR was used as the detection system, and injection of CAP and, to a lesser degree, thiamphenicol resulted in proportional displacement of the conjugate, which was detected at 460 nm. The detection system showed a linear response over a range of 3-1000 μg/mL and effectively detected CAP extracted from serum. This system offers a tailor-made, selective, and rapid method for CAP detection, is able to discriminate between similar molecules, and is effective below and above the therapeutic range (10-20 μg/mL serum, potentially toxic above 25 μg/mL). This technique is quite general and should enable the use of MIPs in a wide variety of applications involving the detection of families of molecules which possess a distinct arrangement of functional groups.     

牺牲硅胶骨架法制备盐酸黄连素印迹聚合物及其性能研究

以盐酸黄连素（berberine-C1）为模板分子,硅胶为牺牲载体,甲基丙烯酸（MAA）或4-乙烯基吡啶（4-VP）、二甲基丙烯酸乙二醇酯（EDMA）及偶氮二异丁腈（AIBN）分别为功能单体、交联剂及引发剂制备了黄连素印迹聚合物。用光学显微镜观察了聚合物形貌,红外光谱（IR）研究了印迹聚合物（Mip）对模板分子的再结合...     

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.     

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。     

Bioimprinting of polymers and sol-gel phases. Selective detection of yeasts with imprinted polymers

Coated quartz crystal microbalances were modified with a surface-imprinting process using whole yeast cells. These molded polymer and sol-gel surfaces show honeycomb-like structures as shown by atomic force microscopy. Reinclusion of cells allows a selective on-line monitoring of these microorganism concentrations in water over 5 orders of magnitude. The sensitivity to cells holds up in growth media up to 21 g/L. Even cell fragments can be detected in flowing conditions. The highly robust polymers on the sensor devices are suitable for biotechnological applications.     

Extraction and purification of penicillin G from fermentation broth by water-compatible molecularly imprinted polymers

Highly selective molecularly imprinted polymer (MIP) was synthesized by using methacrylic acid as functional monomer, trimethylolpropane trimethacrylate as cross-linker, chloroform as porogen and penicillin G potassium as template molecule. These imprinted polymers were used as solid-phase extraction sorbent for the selective extraction of penicillin G from the fermentation broth samples. Various parameters affecting the extraction efficiency of the MIP particles such as; effects of pH, wash and eluent solutions were evaluated. Molecular recognition properties and selectivity of these MIPs were estimated and the obtained results revealed high affinity for the target antibiotic. Equilibrium binding experiments were done to assess the performance of the MIP relative to non imprinted polymer (NIP). After optimizing the extraction parameters in molecularly imprinted solid-phase extraction (MISPE), successful imprinting was confirmed by comparison of the recoveries from the fermentation broth, ranging between 24–26% (RSD 4.1–4.5%, n = 4) for the NIPs and 83–88% (RSD 3.1–3.4%, n = 4) for the MIPs.     

新型分离材料硅胶表面分子印迹聚合物的制备

本文研究了一种新的基于硅胶表面修饰的分子印迹聚合物制备方法。首先在硅胶表面共价键引进硅氧烷,利用硅氧烷的端基官能团与偶氮(4'氰基戊酸)进一步反应,在硅胶表面引进偶氮引发剂。然后采用分子印迹技术,以甲基丙烯酸为功能单体和乙二醇二甲基丙烯酸酯为交联剂,在硅胶表面合成了对D苯丙氨酸具有选择性结合能力的表面分子印迹的新型分离材料。并用平衡吸附实验研究了其吸附性能。结果表明:该聚合物对D苯丙氨酸有较高的亲和性、选择性、吸附量,可用于分离领域如色谱填料、固相萃取等。     

Thermometric sensing of peroxide in organic media. Application to monitor the stability of RBP-retinol-HRP complex

The stability of horseradish peroxidase (HRP) in aqueous and organic solvents is applied to develop a simple thermometric procedure to detect the binding of retinoic acid-HRP conjugate to retinol binding protein (RBP). Butanone peroxide (BP) in organic phase and hydrogen peroxide in aqueous phase is detected thermometrically on a HRP column, immobilized by cross-linking with glutaraldehyde on controlled pore glass (CPG). Acetone, acetonitrile, methanol, and 2-butanol are used for detection of BP, in the flow injection analysis (FIA) mode. A linear range between 1 and 50 mM BP is obtained in all the organic solvents with a precision of 5-7% (CV%). The magnitude and nature of the thermometric response is significantly different in each organic solvent. The stability of HRP in the organic phase is used to study the stability of a retinoic acid-HRP conjugate bound to immobilized RBP. The response of HRP (to 20 mM BP) in the retinoic acid-HRP conjugate is used as an indicator of the stability of the RBP-retinoic acid-HRP complex, after challenges with various organic/aqueous solvents. Both immobilized HRP and RBP are stable at least for 6 months. The effect of o-phenylene diamine on the thermometric response of HRP is also investigated. A scheme for the design of a thermometric retinol (vitamin A) biosensor is proposed.     

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.     

Investigation of the effect of relative humidity on polymers by depth sensing indentation

Stereolithography (SL) resins absorb varying amounts of moisture dependent on the relative humidities, which can significantly affect the mechanical properties. In this work, the influence of relative humidity (RH) on the mechanical behaviour of an SL resin is investigated using depth sensing indentation (DSI). The samples were conditioned by two methods. In the first method, samples were pre-conditioned at 33.5, 53.8, 75.3 and 84.5% RH using saturated salt solutions. These preconditioned samples were tested at 33.5% RH, using a humidity control unit (HCU) to control RH in the DSI system. In the second method, samples were conditioned and tested at 33.5, 53.8, 75.3 and 84.5% RH by regulating humidity in the DSI system using the HCU. Temperature was kept constant at 22.5 °C for the conditioning and DSI testing. It was seen that hardness and modulus decreased with increasing RH and conditioning time but recovered significantly when tested after drying. This study demonstrates that RH needs to be taken into account during the DSI testing of polymers.