Fabrication of pH‐responsive molecularly imprinted polyethersulfone particles for bisphenol‐A uptake

pH‐responsive molecularly imprinted particles were successfully fabricated by pore‐filling poly (acrylic acid) (PAA) gels into bisphenol‐A (BPA)‐imprinted polyethersulfone particles. The adsorbed BPA amount (or rate) decreased after filling the PAA gels both for the imprinted and nonimprinted particles. However, it was confirmed that changing the acidity of the solution reversibly controls the rebinding ability toward BPA and that the BPA uptake of the pore‐filled particles exhibited chemical valve behavior at a pH between 3 and 6. This finding can be attributed to the swelling of the PAA gels in the particles. The present methodology provides a simple way to prepare pH‐responsive molecularly imprinted materials and is expandable to the imprinting of other hydrophobic molecules, such as dibenzofuran. Also, the results of this work demonstrate the potential of stimuli‐responsive molecularly imprinted polymer materials as smart chemicals and as drug‐delivery systems. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Molecularly imprinted poly(MAA‐co‐AM) composite membranes for selective recognition of nicosulfuron herbicide

Molecularly imprinted membranes with different ratio of acrylamide (AM) versus methacrylic acid (MAA) were prepared by photocopolymerization on commercial filter paper using nicosulfuron as the template. The structures, the thermal stability, and the morphology of membranes were characterized by infrared spectroscopy (IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. Static equilibrium binding and competitive recognition properties of the membranes to nicosulfuron and its analogs (pyrazosulfuron ethyl and bensulfuron methyl) were tested. The results showed that nicosulfuron‐imprinted membranes had the best recognition capacity to nicosulfuron compared with its analogs. The biggest selectivity factors of ${\rm \alpha }_{{\rm N}_{\rm 1} /{\rm P}_{\rm 2} }$ and ${\rm \alpha }_{{\rm N}_{\rm 1} /{\rm B}_{\rm 3} }$ were 1.28 and 1.83 and the imprinted factor reached to 2.34. The results of this study implied that the molecularly imprinted composite membranes could be used as separation membranes for nicosulfuron enrichment. The Scatchard plot revealed that one class of binding sites was mainly produced in the imprinted composite membrane in the studied concentration range of nicosulfuron. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

氯霉素分子印迹复合膜的制备及其吸附性能研究

利用分子印迹原位聚合法,在紫外光引发下,以氯霉素为模板分子,以甲基丙烯酸二乙基氨基乙酯为功能单体,以乙二醇二甲基丙烯酸酯为交联剂,以偶氮二异丁腈为引发剂,以尼龙微孔滤膜为载体,制备了具有选择识别性的氯霉素印迹聚合物复合膜;采用紫外光谱分析研究了模板分子和功能单体之间的作用,并对印迹聚合物复合膜进行了平衡吸附和特异性吸附实验,以研究其识别能力。结果表明,氯霉素和甲基丙烯酸二乙基氨基乙酯之间形成了非共价键;合成的印迹复合膜对氯霉素分子表现出了高度的识别能力和良好的特异吸附性,吸附结合量达到1.753 g/cm2。     

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     

分子印迹膜分离技术进展

分子印迹膜是分子印迹技术与膜分离相结合的一种新型的分离膜,具有高度的特异性分子识别能力,在分离工程中有着巨大的潜能。本文介绍了分子印迹技术的基本原理和分子印迹膜的结构特点,分析了分子印迹膜的两种传质机理,“延迟”效应和“促进”效应,简介了当前的研究及应用进展,包括了制备组成的优化手段,实现自组装的主要的合成方法、复合材料的开发以及在药物分离中的应用,提出了分子印迹膜当前存在的问题,最后对其发展进行了展望。     

Preparation and characterisation of a novel copper‐imprinted polymer based on β‐cyclodextrin copolymers for selective determination of Cu2+ ions

A novel ion‐imprinted polymer (IIP) using (6‐O‐butene diacid ester)‐β‐cyclodextrin (β‐CD‐MAH) as the functional monomer and copper ions as the template was developed for Cu²⁺ sensing. First, reactive β‐cyclodextrin (β‐CD) monomers with vinyl carboxylic acid functional groups were synthesised and were co‐polymerised with styrene via radical polymerisation. Then, the β‐CD copolymers were complexed with Cu²⁺ in order to obtain the IIP. The imprinting effect was realised by removing the template ions from the imprinted polymer. The structure, composition and morphology of the IIP were characterised by Fourier transform IR spectroscopy, energy‐dispersive spectroscopy and field‐emission SEM. The adsorption capacity was investigated by UV–visible spectroscopy in batch operation mode. The maximum adsorption capacity for the Cu²⁺ template ions was 28.91 mg g^?1, and the adsorption selectivity was clearly illustrated from the increased sorption affinity towards Cu²⁺ ions over other competing ions. The adsorption was affected by the pH of the aqueous medium, and enhanced adsorption capacity was observed at pH 5. The prepared IIP could be used 10 times after its regeneration without significant loss of the adsorption capacity. © 2018 Society of Chemical Industry     

Evaluation of mixed‐conducting lanthanum‐strontium‐cobaltite ceramic membrane for oxygen separation

In this study, La_0.4Sr_0.6CoO_3‐δ (LSC) oxide was synthesized via an EDTA‐citrate complexing process and its application as a mixed‐conducting ceramic membrane for oxygen separation was systematically investigated. The phase structure of the powder and microstructure of the membrane were characterized by XRD and SEM, respectively. The optimum condition for membrane sintering was developed based on SEM and four‐probe DC electrical conductivity characterizations. The oxygen permeation fluxes at various temperatures and oxygen partial pressure gradients were measured by gas chromatography method. Fundamental equations of oxygen permeation and transport resistance through mixed conducting membrane were developed. The oxygen bulk diffusion coefficient (D_v) and surface exchange coefficient (K_ex) for LSC membrane were derived by model regression. The importance of surface exchange kinetics at each side of the membrane on oxygen permeation flux under different oxygen partial pressure gradients and temperatures were quantitatively distinguished from the oxygen bulk diffusion. The maximum oxygen flux achieved based on 1.6‐mm‐thick La_0.4Sr_0.6CoO_3‐δ membrane was ～4.0 × 10^?7 mol cm^?2 s^?1at 950°C. However, calculation results show theoretical oxygen fluxes as high as 2.98 × 10^?5 mol cm^?2 s^?1 through a 5‐μm‐thick LSC membrane with ideal surface modification when operating at 950°C for air separation. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Characterization of molecularly imprinted and nonimprinted polymer submicron particles specifically tailored for removal of trace 17β‐estradiol in water treatment

This study investigated the potential use of molecularly imprinted polymer (MIP) submicron particles for the selective removal of trace 17β‐estradiol (E2) in water treatment. Methacrylate‐based MIP submicron particles were synthesized, in a one‐step suspension polymerization procedure, using ethylene glycol dimethacrylate (EGDMA) as the cross‐linker. After template removal, the particles could be used as a smart material for specific binding of E2. The submicron size of MIP particles facilitated uniform dispersion in water for up to 17 days. These particles were meritorious in mass transfer behavior, allowing phase partitioning of E2 molecules in water during a short treatment time. After 1‐mL water samples of different E2 concentrations were treated with 20 mg of MIP particles for 2 min, recovery percentages as high as 97% ± 3% were achieved. The specific binding capacity of these MIP particles was determined to be 15 mg E2/g. Nonimprinted polymer nanoparticles were also evaluated for nonspecific binding of E2, using 0.5 mg in 1 mL of water, to attain 64% ± 3% efficiency in 3 min towards general water treatment. A simple capillary electrophoresis method was successfully developed for the characterization of MIP and NIP particles. Apparently the less negative the electrophoretic mobility, the higher binding efficiency and faster binding kinetics the particles would exhibit with E2 due to less hindered Brownian diffusion. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Guided tissue regeneration with use of β‐TCP/chitosan composite membrane

Guided tissue regeneration (GTR) membranes with bioabsorbable characteristics have been employed, in recent years, for periodontal procedures to deflect the growth of gingival tissues away from root surface. They provide an isolated space over regions with defective tissues and allow the relatively slow growing periodontal ligament fibroblasts to be repopulated over the root surface. In this study, we have employed chitosan and tricalcium phosphate (β‐TCP) as viable membrane materials and evaluated their roles in GTR applications. Three types of β‐TCP/chitosan membranes, weight ratio of β‐TCP/chitosan 65 : 35, 33 : 67, and 10 : 90, were prepared for three categories: the mechanical strength to create an effective space; the rapid rate to reach hydrolytic equilibrium in phosphate buffer solution; and the ease of clinical manipulations. Consequently, standardized, transosseous, and critical‐sized (cavity of 8 mm) skull defects were made in adult rabbits, and the defective regions were covered with the specifically prepared chitosan membranes. After 4 weeks of recovering, varying degrees of bone healing were observed beneath the β‐TCP/chitosan membranes in comparison to the control group. The β‐TCP/chitosan membranes covered regions showed a clear boundary space between connective tissues and bony tissues. Over all, good cell‐occlusion and beneficial osteogensis effects by these bioabsorbable materials toward the wound recovery were indicated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Chiral separation of D,L‐serine racemate using a molecularly imprinted polymer composite membrane

Molecularly imprinted (MIP) composite membranes were prepared using conventional interfacial polymerization technique that has been often used for the preparation of reverse osmosis (RO) membrane. Target molecules (D ‐serine) were used together with the piperazine (PIP) and Trimesoyl chloride (TMC) for the interfacial polymerization of the active layer with chiral spaces in it on the surface of the polysulfone ultrafiltration membranes. After formation of the polyamide composite membranes, the target molecules in the active layers were removed and MIP composite membranes were prepared. The MIP membranes prepared so were then characterized with analytical methods and proved to be effective for the selective permeation of D ‐serine. When serine racemate was used for optical resolution, the diffusion rate of the D ‐serine appeared to be faster than that of the L ‐serine and in permeates, the concentration of the D ‐serine increased with operation time. When the operating time reached 60 h, enantiomeric excess (% ee) of the serine mixture in permeates became about 80%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1866–1872, 2007     

Towards a new strategy of a chitosan‐based molecularly imprinted membrane for removal of 4‐nitrophenol in real water samples

The issue of water contaminants, which affects human and environmental health, is not trivial. It is thus paramount to find new cheap and user friendly ways to detect and remove them from the environment. Here, the synthesis of a green chitosan (CS ) based molecularly imprinted membrane for the detection and quantification of 4‐nitrophenol (4‐NO₂Ph ) in aqueous media is proposed. The concentration of 4‐NO₂Ph in a water solution was measured by HPLC analysis. CS as a functional polymer, 4‐NO₂Ph as template, 4‐[(4‐hydroxy)phenylazo]benzenesulfonic acid as ligand, and glutaraldehyde as crosslinker in the presence of polyethylene glycol as porogen were used. The membrane was characterized by SEM and Fourier transform IR analyses, which confirmed the CS and polyethylene glycol backbone of the membrane. Kinetic studies of the detection system were performed by using pseudo‐first‐order and pseudo‐second‐order models. Then, the binding efficiency between 195.33 µmol L^?1 and 9235.55 µmol L^?1 of 4‐NO₂Ph was evaluated, finding a maximum adsorption of 723.25 µmol 4‐NO₂Ph per gram of membrane consistent with the Q _max calculated from the Langmuir isotherm. The selectivity of the membrane versus three phenolic competitor molecules, sharing very similar molecular structure to 4‐NO₂Ph , was demonstrated. Finally, the applicability of the membrane to real‐world samples was evaluated, by using drinking water spiked with 7.19 µmol L^?1 of 4‐NO₂Ph , obtaining a removal efficiency of 70.6%. © 2017 Society of Chemical Industry     

Separation of bovine serum albumin (BSA) using γ‐Al2O3–clay composite ultrafiltration membrane

BACKGROUND: Ceramic membranes have received more attention than polymeric membranes for the separation and purification of bio‐products owing to their superior chemical, mechanical and thermal properties. Commercially available ceramic membranes are too expensive. This could be overcome by fabricating membranes using low‐cost raw materials. The aim of this work is to fabricate a low‐cost γ‐Al₂O₃–clay composite membrane and evaluate its potential for the separation of bovine serum albumin (BSA) as a function of pH, feed concentration and applied pressure. To achieve this, the membrane support is prepared using low‐cost clay mixtures instead of very expensive alumina, zirconia and titania materials. The cost of the membrane can be further reduced by preparing a γ‐alumina surface layer on the clay support using boehmite sol synthesized from inexpensive aluminium chloride instead of expensive aluminium alkoxide using a dip‐coating technique. RESULTS: The pore size distribution of the γ‐Al₂O₃‐clay composite membrane varied from 5.4–13.6 nm. The membrane was prepared using stable boehmite sol of narrow particle size distribution and mean particle size 30.9 nm. Scanning electron microscopy confirmed that the surface of the γ‐Al₂O₃–clay composite membrane is defect‐free. The pure water permeability of the support and the composite membrane were found to be 4.838 × 10^?6 and 2.357 × 10^?7 m³ m^?2 s^?1 kPa^?1, respectively. The maximum rejection of BSA protein was found to be 95%. It was observed that the separation performance of the membrane in terms of flux and rejection strongly depends on the electrostatic interaction between the protein and charged membrane. CONCLUSION: The successively prepared γ‐Al₂O₃‐clay composite membrane proved to possess good potential for the separation of BSA with high yield and could be employed as a low cost alternate to expensive ceramic membranes. Copyright © 2009 Society of Chemical Industry     

Transport selectivity of tribenuron‐methyl imprinted polymer nanowire membrane prepared using N,O‐bismethacryloyl ethanolamine as a functional crosslinking monomer

Using tribenuron‐methyl as a template and N,O‐bismethacryloyl ethanolamine as a functional crosslinking monomer, a molecularly imprinted nanowire membrane was prepared over an anodic alumina oxide membrane. The nanowire fabric of the imprinted membrane was established with a scanning electron microscope and a transmission electron microscope. However, the nonimprinted particulate membrane is formed in the absence of a template. Scatchard analysis showed that an equal class of binding sites were formed in the imprinted nanowire membrane and the dissociation constant and the maximum number of these binding sites were estimated to be 1.44 × 10⁻⁵ M and 22.7 µmol/g, respectively. The permeation experiments throughout the imprinted membrane and the nonimprinted one were carried out in a solution containing the template and its competitive analogs. These results demonstrated that the molecularly imprinted nanowire membrane exhibited higher transport selectivity for the template tribenuron‐methyl than its analogs, chlorimuron‐ethyl, thifensulfuron‐methyl and N‐(4‐bromophenylcarbamoyl)‐5‐chloro‐1H‐benzo[d]imidazole‐2‐carboxamide. But the nonimprinted granular membrane had no permselectivity for the four substrates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

β‐cyclodextrin/poly(vinyl alcohol) hydrogels containing phenylpropionic acid and naphthylamine: dual pH‐sensitive release

Hydrogel composed of β‐cyclodextrin (β‐CD) and poly(vinyl alcohol) was prepared in a strong alkaline condition using epichlorohydrin as a crosslinker. Phenylpropionic acid (PPA) and naphthylamine (NA) were loaded in the cavities of β‐CD residues to endow the hydrogel with a dual pH‐sensitive characteristic. In release experiments using fluorescein isothiocyanate‐dextran (FITC‐dextran) as a dye, PPA/NA‐loaded hydrogel exhibited an extensive release not only in acidic conditions (e.g. pH 3.0) but also in alkaline conditions (e.g. pH 9.0). PPA and NA will be highly ionized at the alkaline and the acidic pH and they could promote swelling of the hydrogel, causing an extensive release at those pH values. However, the release was suppressed at mid pH values (e.g. pH 5.0 and pH 7.4), possibly due to the formation of salt bridges between PPA^? and NA⁺. In fact, the degree of swelling at mid pH was lower than that observed at strong acidic pH and alkaline pH. According to SEM images, the pore size and the texture compactness of hydrogels which had been subjected to swelling at different pH values could also account for the dual pH‐sensitive releases. The hydrogels exhibited dual pH sensitivities in terms of FITC‐dextran release and swelling. These hydrogels might be used as a pH‐sensitive vehicle for water‐soluble drugs. © 2013 Society of Chemical Industry     

3,3′‐Diindolylmethane imprinted polymers: synthesis,characterization and analytical procedure for template isolation from biological matrix

A novel sorbent for the separation of 3,3′‐diindolylmethane (DIM) has been developed. DIM was used as a template molecule to prepare twelve imprinted polymers from seven different functional monomers in six various porogens in the presence of ethylene glycol dimethacrylate as a crosslinker. The binding capacity showed that the highest binding specificity was achieved when allylamine as the monomer and carbon tetrachloride as the porogen were used to form bulk polymers. Binding capacities were 130.4 ± 2.8 µg g^?1 for imprinted MIP7_a polymer versus 49.03 ± 0.44 µg g^?1 for non‐imprinted NIP7_a polymer. An imprinting factor of 3.12 reflected the high specificity of MIP7_a. A solid‐phase extraction protocol was fully optimized. Two methanol–water systems were selected as the most effective for loading and washing steps, while acetonitrile was chosen as the most efficient eluent suitable for recovery of 91.7 ± 3.8% of DIM. Optimal concentration of DIM and volume of loaded sample were also examined. A loaded volume of 2.5 mL was the most appropriate for 0.625 and 1.25 mg L^?1. The use of MIP7_a for the separations of DIM from spiked bovine serum albumin was evaluated, showing a total recovery of 87.7 ± 3.5%. The commercial sorbent C18 was not suitable for such an application. © 2013 Society of Chemical Industry     

Cd2+, Cu2+, Pb2+, Sr2+, and Y3+ binding characteristics of 17β‐estradiol molecularly imprinted polymer particles incorporated with dicyclohexano‐18‐crown‐6 for urine bioassay

The metal ion binding characteristics of molecularly imprinted polymer (MIP) submicron particles prepared using 17β‐estradiol (E2) as a template, and incorporated with dicyclohexano‐18‐crown‐6 (DCH18C6), were studied using differential pulse anodic stripping voltammetry. When Sr²⁺ was added to DCH18C6‐E2‐MIP particles already occupied by Cd²⁺, Cu²⁺, and Pb²⁺ inside the binding sites, a displacement reaction was observed: Cd²⁺/Cu²⁺/Pb²⁺‐DCH18C6‐E2‐MIP + Sr²⁺ = Sr²⁺‐DCH18C6‐E2‐MIP + Cd²⁺/Cu²⁺/Pb²⁺. This demonstrated that DCH18C6 had stronger binding affinity for Sr²⁺ than Cd²⁺ Cu²⁺ or Pb²⁺. Strong DCH18C6 binding affinity was also observed for Y³⁺. Atomic emission spectrometry showed that DCH18C6‐E2‐MIP particles (150 mg/mL) resulted in 52% binding of Sr²⁺ (2000 ppm, at pH 6.3 ± 0.1 and ionic strength of 0.1M NaNO₂). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011