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     

Clozapine recognition via molecularly imprinted polymers; bulk polymerization versus precipitation method

Two clozapine (CLZ) imprinted polymers were prepared by bulk and precipitation methods. Methacrylic acid and ethylene glycol dimethacrylate (EDMA) were used as functional and crosslinker monomers, respectively. The mean diameter and particle size distribution of the imprinted (P‐MIP) and nonimprinted (P‐NIP) particles obtained in precipitation method were examined. A conventional batch‐adsorption test was applied for characterization of CLZ–polymer interaction. Dissociation constant (K_D) and maximum binding sites (B_max) were calculated using Scatchard analysis. To evaluate the recognition properties of polymers, phenytoin (PTN) binding to each polymer was also studied and compared to CLZ. The imprinting factor (IF) and selectivity factor (α) were also determined for each polymer. Average diameter and polydispersity of P‐MIP were 925 nm and 0.17, respectively. The data for P‐NIP were 1.05 μm and 0.18. The K_D, IF, and α values calculated for P‐MIP were 0.45 μM, 3.26, and 17.43, respectively. The data for imprinted polymer, prepared by bulk polymerization (B‐MIP), were 14.5 μM, 1.95, and 3.67. These results demonstrated that precipitation polymerization is a more convenient, more effective, and more reproducible method than bulk polymerization for the synthesis of uniformly sized micron and submicron‐imprinted polymer particles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of uniform molecularly imprinted polymer beads for separation of triazine herbicides

Uniform molecularly imprinted polymer beads were synthesized by precipitation polymerization for separation of triazine herbicides. A series of imprinted polymers were prepared using ametryn as template and divinylbenzene as crosslinking monomer, in combination with three different functional monomers under different solvent conditions. Under optimized reaction conditions, we obtained uniform molecularly imprinted polymer microspheres that display favorable molecular binding selectivity for triazine herbicides. The imprinted polymer beads synthesized using methacrylic acid as functional monomer in a mixture of methyl ethyl ketone and heptane showed the best results in terms of particle size distribution and molecular selectivity. Compared with nonimprinted polymer microspheres, the imprinted microspheres displayed significantly higher binding for a group of triazine herbicides including atrazine, simazine, propazine, ametryn, prometryn, and terbutryn. For the first time, precipitation polymerization has been used to produce highly uniform imprinted microspheres suitable for affinity separation of triazine herbicides. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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。     

Computer simulation and preparation of molecularly imprinted polymer membranes with chlorogenic acid as template

A computational approach was developed for screening functional monomers for rational design of molecularly imprinted polymer (MIP) membranes. It was based on a comparison of the binding energy of complexes between a template and various functional monomers. According to the results of theoretical calculations, MIP membranes with chlorogenic acid as a template were prepared with a UV irradiation polymerization method, using 4‐vinylpyridine as a functional monomer and N,N′‐methylenebisacrylamide as a crosslinker, with poly(vinylidene fluoride) microfiltration membranes as the support. Membranes covered with a thin layer of imprinted polymer selective to chlorogenic acid were then obtained and tested using the equilibrium‐adsorption method. The high affinity of these synthetic membranes to chlorogenic acid, together with their straightforward and inexpensive preparation, provides a good basis for the development of applications of imprinted polymers in separation processes such as solid‐phase extraction. Copyright © 2011 Society of Chemical Industry     

Synthesis and characterization of 3,4‐dihydroxyphenylacetic acid imprinted polymers

Eight molecularly imprinted polymers (MIP1–MIP8) were synthesized with different functional monomers and porogens using 3,4‐dihydroxyphenylacetic acid (DOPAC) as a template. Thermal, radical bulk polymerization was employed in the presence of ethylene glycol dimethacrylate as a cross‐linker. A computational analysis indicated that complexes with four molecules of 4‐vinylpyridine, 1‐vinylimidazole and acrylonitrile had high positive enthalpies of formation. The polymers synthesized with these monomers showed an imprinting factor below 1. Polymer MIP8 synthesized with allylamine as the functional monomer, with the highest energy of interaction with DOPAC, was characterized by the highest imprinting factor equal to 1.91. Examination of the binding ability of DOPAC and a group of structurally related compounds showed that the strong interactions between amine groups in the polymer and carboxylic groups in the analyte governed the recognition mechanism. The Langmuir adsorption model and the pseudo‐second‐order mechanism properly evaluated the MIP8 and non‐imprinted polymer 8 adsorption characteristics. Scatchard analysis revealed that MIP8 had two classes of heterogeneous binding sites with K_d(1) = 0.12 µmol L^?1 and K_d(2) = 1.46 µmol L^?1. Finally, the potential application of MIP8 for separation of DOPAC was demonstrated. Copyright © 2011 Society of Chemical Industry     

单体对分子印迹聚合物分子识别能力的影响：量子化学计算与实验研究

采用密度泛函方法计算功能单体与印迹分子的结合能,以与目标分子结合能最大的单体分子来合成分子印迹聚合物.为此,以茶碱为印迹分子,氯仿为溶剂,首先计算了茶碱与甲基丙烯酸、丙烯酰胺和三氟甲基丙烯酸的结合能,其强度顺序为：三氟甲基丙烯酸 > 甲基丙烯酸 > 丙烯酰胺.然后以茶碱为印迹分子、氯仿为溶剂、二甲基丙烯酸乙二醇酯为交联剂,分别采用上述3种单体合成分子印迹聚合物并测定了其分子识别能力,实验结果和量子化学计算结果具有一致性.最后,采用1H NMR考察了茶碱和上述3种单体之间的氢键作用,揭示出二者相互作用的内在机制.研究结果表明量子计算方法可以应用于合成分子印迹聚合物时单体的选择.     

Synthesis of poly[N′‐(2‐cyanoacetyl)acrylohydrazide] and its copolymers with styrene and N‐phenylacrylamide: Characterization,complexation, thermal stability,swelling, and morphology

N′‐(2‐cyanoacetyl)acrylohydrazide (CAH) was obtained with the treatment of 2‐cyanoacetohydrazide with acryloyl chloride in acetonitrile. The obtained acrlyoyl derivative was transferred to the corresponding polymer, poly[N′‐(2‐cyanoacetyl)acrylohydrazide] (PCAH), through treatment with 2,2′‐azobisisobutyronitrile at 75°C. Copolymers with styrene or N‐phenyl acrylamide monomers were synthesized with different ratios. The structures of these polymers were characterized with elemental analysis and spectral data. The morphology, metal uptake, and ion selectivity of the polymers were studied. In addition, the swelling behavior of the polymer and metallopoymer complexes at different times of drying was also investigated. Thermogravimetric analysis of the polymer and polymer complexes under air reflected that PCAH–Pb was the most stable, followed by PCAH, PCAH–Hg, PCAH–Cu, PCAH–Ni, and PCAH–Co. A similar stability with little difference was reported under nitrogen. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Interaction of molecularly imprinted polymers with creatinine

Memory sites toward clinically relevant creatinine have been imparted in polymers based on methacrylic acid, N-vinyl pyrrolidine, and 2-hydroxy ethyl methacrylate by the technique of molecular imprinting. The polymers are subjected to interaction with creatinine and creatine, a molecule of close resemblance with creatinine. The results show that selectivity is largely governed by the nature of the monomer. The reusability of the polymer is also demonstrated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2539–2542, 1997     

Preparation and characterization of molecularly imprinted polymer of bovine serum albumin

Molecularly imprinted polymer beads of bovine serum albumin (BSA) were prepared via inverse phase suspension polymerization, using BSA as the template molecule, a combination of acrylamide and methacrylic acid (MAA) as double functional monomers, and N, N′‐methylene bisacrylamide as the crosslinker. The effect of different monomer ratios and degrees of crosslinking were investigated. When both selectivity and physical properties of the resultant polymer beads were taken into account, the ratio of MAA in the total monomers was chosen at 40% (m/m) and the degree of crosslinking at 30% (n/n), the resultant polymer beads had good selectivity (α = 2.77) and good physical properties. The effects of pH and temperature were studied. It turned out that the functionalization of polymers of BSA prepared via inverse‐phase suspension polymerization exhibited specific recognition for BSA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Computer simulation and synthesis of stimuli‐responsive polymer by sol‐gel for selective recognition of (4‐chloro‐2‐methylphenoxy)acetic acid

A novel photoresponsive functional monomer bearing a siloxane polymerizable group and azobenzene moieties was synthesized, and then photoresponsive molecularly imprinted sol‐gel polymers were successfully fabricated from the synthesized functional monomer, using (4‐chloro‐2‐methylphenoxy)acetic acid (MCPA) as a molecular template. The photoisomerization properties of the functional monomer are retained after incorporation into the rigid three‐dimensional crosslinked polymer matrix. The template is then removed from the resulting polymer to generate pores, which are complementary to the template in shape, size and functionality. The substrate affinity of the molecularly imprinted polymer (MIP) receptor sites is photoswitchable. This can be attributed to the photoisomerization of azobenzene chromophores within the MIP receptors, resulting in alteration of their geometry and the spatial arrangement of their binding functionalities. The binding affinity of the imprinted recognition sites was switchable by alternate irradiation with UV and visible light, suggesting that azobenzene groups located inside the binding sites could be used as chemical sensors and the trans–cis isomerization could regulate the affinity for MCPA. To study the hydrogen bond interactions between template molecules and functional monomer, computational molecular modeling was employed. The data indicate that the design of the MIP is rational. Copyright © 2012 Society of Chemical Industry     

Creating a macromolecular receptor by affinity imprinting

A molecularly imprinted polymeric receptor for trypsin was synthesized by employing a novel technique that is a combination of affinity separation and molecular imprinting. An enzyme–inhibitor complex of trypsin and N‐acryloyl para‐aminobenzamidine was polymerized with acrylamide and N,N'‐methylene bis‐acrylamide. Template trypsin was extracted out to obtain an affinity‐imprinted polymer. Control experiments were performed to demonstrate the synergistic affinity‐imprinting effect. The percentage of crosslinker used was the crucial factor in determining the imprinting efficacy of the polymers. Imprinted polymer containing 50% crosslinker exhibited a linear Scatchard plot. Unlike non‐imprinted gel, the receptor exhibited almost exclusive recognition of trypsin in an individual batch experiment as well as from a mixture of trypsin and chymotrypsin. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1075–1083, 2001     

The use of metal‐containing monomer in the preparation of molecularly imprinted polymer to increase the adsorption capacity

Molecular imprinting is an elegant approach to induce antibody like recognition ability in synthetic polymers. The technique of molecular imprinting has been used extensively in the preparation of tailor‐made stationary phases in chromatography, sorbents in solid phase extraction, sensor elements, etc. Though several of the reported molecularly imprinted polymers (MIPs) possess substrate selectivity comparable to antibodies, they are poor in adsorption capacity. The adsorption capacity could be improved presumably through enhanced interaction between the functionalities of the monomers and the print molecule. A simple approach to improve the interaction is perhaps the use of chemically modified monomers in the synthesis of the MIPs. This article explores this possibility by using a metal‐containing monomer in the synthesis of MIP. The data obtained using a copper acrylate based MIP and cholesterol as substrate indicates the adsorption capacity can be improved considerably through the simple chemical modification of the functional monomer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2795–2799, 2001     

Computationally designed monomers and polymers for molecular imprinting of theophylline and its derivatives. Part I

The main objective of this research was to develop and apply state-of-the-art computational tools to achieve an understanding of intermolecular interactions in molecular imprinting of theophylline into complex polymeric systems. Molecular dynamics (MD) simulations were carried out for different molecular systems in order to predict the interaction energies, the closest approach distances and the active site groups between the simulated molecular systems and different bio-ligands. The minimized structures of five ligands, theophylline and its derivatives (theobromine, theophylline-8-butanoic acid, caffeine and theophylline-7-acetic acid) have been obtained with the use of molecular mechanics approach. NVT MD simulations at room temperature were carried out to obtain equilibrated conformations in all cases.The first simulated molecular systems consisted of a ligand and a commonly used functional monomer, such as acrylic acid, methacrylic acid, acrylamide, acrolein, acrylonitrile, styrene, etc. (a total number of 25 monomers were simulated). For each of the simulated monomer, molecular clusters consisting of 10 monomers were built. For each pair of molecular systems, (10 monomers with a ligand and 10 monomers without a ligand) a total energy difference, (ΔE), was calculated in order to estimate the interaction energy between a ligand and the corresponding monomers. The second simulated molecular systems consisted of a ligand and a polymer. For each of the simulated polymers, a polymeric chain with degree of polymerization (DP) 10 was simulated with theophylline or its derivative and the interaction energy (ΔE) was calculated. From simulated polymer systems it was found that just poly(acrylic acid) and poly(itaconic acid) are selective only for theophylline. The functional groups of monomers interacting with ligands are -COOH or CH₂CH-. The functional groups of polymers are predominantly -COOH. In the case of poly(acrylic acid) and poly(itaconic acid) the distance of closest approach between a polymer and theophylline was between 2.0 and 4.0 Å.     

Addition‐cure‐type phenolic resin based on alder‐ene reaction: Synthesis and laminate composite properties

A maleimide‐functional phenolic resin was reactively blended with an allyl‐functional novolac in varying proportions. The two polymers were coreacted by an addition mechanism through Alder‐ene and Wagner–Jauregg reactions to form a crosslinked network system. The cure characterization was done by differential scanning calorimetry and dynamic mechanical analysis. The system underwent a multistep curing process over a temperature range of 110–270°C. Although the cure profiles were independent of the composition, the presence of maleimide led to a reduced isothermal gel time of the blend. Increasing the allylphenol content decreased the crosslinking in the cured matrix, leading to enhanced toughness and improved resin‐dominant mechanical properties of the resultant silica laminate composites. Changing the reinforcement from silica to glass resulted in further amelioration of the resin‐reinforcement interaction, but the resin‐dominant properties of the composite remained unaltered. Increasing the maleimide content resulted in enhanced thermal stability. Integrating both the reactive groups in a single polymer and its curing led to enhanced thermal stability and T_g, but to decreased mechanical properties of the laminate composites. This can be attributed to a brittle matrix resulting from enhanced crosslinking facilitated by interaction of the reactive groups located on the polymer of an identical backbone structure. The cured polymers showed a T_g in the range of 170–190°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 737–749, 2001     

Comparison of thin‐layer and bulk MIPs synthesized by photoinitiated in situ crosslinking polymerization from the same reaction mixtures

The synthesis and comparative characterization of molecularly imprinted polymers (MIPs) in two different formats, as thin layers grafted to the entire surface of polypropylene microfiltration membranes and as conventional particles, are described. Imprinting with atrazine was performed by using itaconic acid and N,N′‐methylene‐bisacrylamide as functional and crosslinker monomers in methanol as the solvent. Polymerization had been initiated by UV irradiation of benzoin ethyl ether and driven to low monomer conversion for the thin‐layer polymers and to high monomer conversion for the bulk materials. The binding performance of MIP composite membranes and of MIP particles packed into cartridges was evaluated in solid‐phase extraction (SPE) experiments of atrazin and simazin from aqueous solutions. The SPE performance depended strongly on pH and buffer concentration. Although an imprinting effect was observed for both formats, the specificity (MIP versus Blank) and the selectivity (atrazin versus simazin) were much higher for the thin‐layer composite membranes than for the bulk polymer particles. In particular, the atrazin/simazin selectivity increased from 32% for the Blank to 78% for the MIP composite membranes. A major reason is the hindered accessibility of the internal pore structure of the particles, whereas the porous filtration membranes are much more compatible with the fast SPE protocol. Furthermore, based on pK_a of the functional carboxylic acid groups—from potentiometric titration and polarity of the binding environment—from fluorescent probe analysis, different properties of the imprinted binding sites can be postulated for the two MIP formats. However, the differences between MIP and Blank were much more pronounced for the thin‐layer composite membranes. The hydrophobic surface of the polypropylene membrane appeared to be a major factor affecting the binding performance of thin‐layer MIPs. The new porous composite membranes could be particularly useful as selective SPE materials in environmental, pharmaceutical, and analytical applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 362–372, 2005     

Synthesis,characterization, and ligating behavior of poly[N,N‐p‐phenylene bisacryl (methacryl)amide]

Monomers of diacylated amine were synthesized by the reaction of acryloyl chloride or methacryloyl chloride with p‐phenylenediamine. Heating DMF solution of these monomers at 75°C in the presence of AIBN as an initiator gave the corresponding polymer. The solid metallopolymer complexes with different metal salts were isolated either by the in situ addition of the monomer, metal salt, and initiator at 75°C or by the reaction of the isolated polymer with the metal salt at 150°C. The monomers, polymers, and their metallopolymer compounds were characterized using elemental analysis, IR, NMR (¹H and ¹³C), and MS spectral measurements in addition to thermal analysis. The IR data showed that the coordinating atoms of the polymer are dependent on the reaction temperature. The ion selectivity of the isolated polymers toward different metal ions either for a single metal ion or in a mixture as aqueous solutions are studied by the batch techniques. Energy dispersive spectroscopy (EDS) measurements showed that both polymers are more selective to Hg²⁺ and Pb²⁺. The morphology of the polymers and their metallopolymer complexes at different temperature was also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2412–2422, 2006     

Synthesis of molecularly imprinted polymers for amino Acid derivates by using different functional monomers

Fmoc-3-nitrotyrosine (Fmoc-3-NT) molecularly imprinted polymers (MIPs) were synthesized to understand the influence of several functional monomers on the efficiency of the molecular imprinting process. Acidic, neutral and basic functional monomers, such as acrylic acid (AA), methacrylic acid (MAA), methacrylamide (MAM), 2-vinylpyridine (2-VP), 4-vinylpyridine (4-VP), have been used to synthesize five different polymers. In this study, the MIPs were tested in batch experiments by UV-visible spectroscopy in order to evaluate their binding properties. The MIP prepared with 2-VP exhibited the highest binding affinity for Fmoc-3NT, for which Scatchard analysis the highest association constant (2.49 × 10(4) M(-1)) was obtained. Furthermore, titration experiments of Fmoc-3NT into acetonitrile solutions of 2-VP revealed a stronger bond to the template, such that a total interaction is observed. Non-imprinted polymers as control were prepared and showed no binding affinities for Fmoc-3NT. The results are indicative of the importance of ionic bonds formed between the -OH residues of the template molecule and the pyridinyl groups of the polymer matrix. In conclusion, 2-VP assists to create a cavity which allows better access to the analytes.     

Synthesis,characterization, and studies on the solid-state crosslinking of functionalized vinyl cinnamate polymers

Functionalized vinyl cinnamate monomers were synthesized by the reaction between hydroxyethylacrylate (HEA) and substituted cinnamoyl chlorides possessing electron releasing and withdrawing functional groups like chloro, methoxy, and nitro groups at the para position of the aromatic ring. The structures of these monomers were characterized by Fourier transform infrared (FTIR), ¹H-, and ¹³C-NMR spectral techniques. The homopolymers of the synthesized monomers were obtained by the free radical solution polymerization in dimethylformamide (DMF) at 80°C for 12 h using azobisisobutyronitrile (AIBN) as a radical initiator. The sensitivity of these polymers towards light was studied by monitoring the photocrosslinking nature of the polymers by ultraviolet (UV) and FTIR techniques. The effect of the functional groups on the crosslinking efficiency was studied and compared with that of the unsubstituted polymer. The cyclobutane-type addition mechanism involved in the photocrosslinking phenomena was confirmed by the above spectral studies in the functionalized vinyl cinnamate polymers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 441–448, 1998     

Photoresponsive Functionalized Vinyl Cinnamate Polymers: Synthesis and Characterization

A series of functionalized vinyl cinnamate monomers were synthesized by the reaction of hydroxyethylmethacrylate and various substituted cinnamoyl chlorides. Electron donating and accepting functional groups such as −OCH₃, −Cl and −NO₂ were introduced at the para position of cinnamoyl chloride. Homopolymerization of the synthesized monomers were carried out in dimethylformamide using azobisisobutyronitrile as a free radical initiator at 80°C for 12h. The structures of the synthesized monomers and their polymers were characterized using Fourier transform infrared (FTIR), ¹H and ¹³C nuclear magnetic resonance spectroscopic techniques. Solid-state crosslinking of the above photosensitive polymers was studied by UV and FTIR spectroscopic techniques. The effects of various functional groups and the addition of sensitizer (benzophenone) on the photocrosslinking nature of the polymers were studied. The mechanism of photocrosslinking is a (2+2)π electron cycloaddition and not cis–trans isomerization in the functionalized polyvinylcinnamates. © 1997 SCI