Abstract: Affinity polymeric adsorbents useful for the separation of compounds which are derivatives of phenols, heterocycles and other compounds containing two polar moieties were prepared by a covalent imprinting approach. Such separation, for example, would facilitate the analytical detection and quantification of each individual compound especially when present in complex sample matrix. The synthetic method, utilised for the preparation of the polymers, is based on co-polymerization of diacrylate esters of hydroxyphenols (catechol, resorcinol and hydroquinone) with an appropriate cross-linker followed by alkaline hydrolysis of the esters and release of the corresponding phenol. The resulting swellable materials contain cavities with adjustable size and orientation of two carboxylic groups suited for the binding of molecules with appropriate size and complementary orientation of polar groups. In contrast to conventional MIPs the synthesized polymers have selectivity not only for the phenolic templates, but also for a group of compounds with suitable orientations of polar functionalities, such as aromatic nitrogen, amino or hydroxyl groups. Polymers demonstrated different affinity to ortho-, meta- and para-isomers of hydroxyphenols, hydroxypyridines and diazine.
Abstract: A new format for the microtiter plate-based assays was proposed. The novelty involves the use of disk-shaped inserts for immobilization of biological and chemical reagents. The internal opening of the disks allows measurements of the reactions by standard microtiter plate readers without any additional steps involving liquid handling. Ideally the plate end-users just have to add the sample and take the measurement without any need of multiple reagent additions or transfer of the liquid to a different plate. The novel assay format also allows handling of reagents which are not soluble in an aqueous environment. As a proof of concept we describe here several model reactions which are compatible with microtiter plate format, such as monitoring enzymatic reactions catalyzed by glucose oxidase (GOx) and urease, measurements of proteins by BCA assay, analysis of pH and concentration of antioxidants. The 'mix and match' approach in the disk-shape format allows multiplexing and could be particularly useful for high throughput screening. One of the potential application areas for this novel assay format could be in a multi-analyte system for measurement of clinically relevant analytes in primary care.
Abstract: Building blocks for a bright future: A new method for the synthesis of organic nanoparticles was developed combining a molecularly imprinted polymer shell and a fluorescent dendrimer biosensing core. Cubic organic nanoparticles are reported for the first time. The polymeric nanoparticles could be used as a direct replacement for antibodies in biosensor applications.
Abstract: Here we present a new and versatile method for the modification of the well surfaces of polystyrene micro-titre plates (microplates) with poly(N-phenylethylene diamine methacrylamide), (poly-NPEDMA). The chemical grafting of poly-NPEDMA to the surface of microplates resulted in the formation of thin layers of a polyaniline derivative bearing pendant methacrylamide double bonds. These were used as the attachment point for various functional polymers through photochemical grafting of various, e.g. acrylate and methacrylate, polymers with different functionalities. In a model experiment we have modified poly-NPEDMA-coated microplates with a small library of polymers containing different functional groups using a two-step approach. In the first step, double bonds were activated by UV irradiation in the presence of N,N-diethyldithiocarbamic acid benzyl ester (iniferter). This enabled grafting of the polymer library in the second step by UV irradiation of solutions of the corresponding monomers in the microplate wells. The uniformity of coatings was confirmed spectrophotometrically, by microscopic imaging and by contact angle measurements (CA). The feasibility of the current technology has been shown by the generation of a small library of polymers grafted to the microplate well surfaces and screening of their affinity to small molecules such as atrazine, a trio of organic dyes and a model protein, bovine serum albumin (BSA). The stability of the polymers, reproducibility of measurement, ease of preparation, and cost-effectiveness make this approach suitable for applications in high-throughput screening in the area of materials research.
Abstract: Here we present the first molecular imprinted polymer (MIP) that is able to attenuate the biofilm formation of the opportunistic human pathogen Pseudomonas aeruginosa through specific sequestration of its signal molecule N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-AHL). The MIP was rationally designed using computational modeling, and its capacity and specificity and that of a corresponding blank polymer toward signal molecule of P. aeruginosa (3-oxo-C12-AHL) and its analogue were tested. The biofilm formation in the presence of polymers and without polymers was studied using scanning confocal laser microscopy. Staining with crystal violet dye was used for the quantification of the biofilm formation. A significant reduction of the biofilm growth was observed in the presence of MIP (>80%), which was superior to that of the resin prepared without template, which showed a reduction of 40% in comparison with biofilm, which was grown without polymer addition. It was shown that 3-oxo-C12-AHL-specific MIP prevented the development of quorum-sensing-controlled phenotypes (in this case, biofilm formation) from being up-regulated. The developed MIP could be considered as a new tool for the elimination of life-threatening infections in a multitude of practical applications; it could, for example, be grafted on the surface of medical devices such as catheters and lenses, be a component of paints, or be used as a wound adsorbent.
Abstract: Here we present a series of molecularly imprinted polymers capable of catalysing the DielsâAlder reaction between benzyl 1,3-butadienylcarbamate (1) and N,N-dimethyl acrylamide (2). The polymer systems studied here demonstrated an unusual cross-linker and temperature dependent behaviour, namely that polymer catalysis of the DielsâAlder reaction was lower at elevated temperature, in contrast to the solution reaction. Furthermore, not only was the catalytic activity significantly influenced by the choice of cross-linker, but in a similar fashion also the extent of the temperature effect, indicating a close relationship between catalysis and the observed inhibition. Molecular dynamics simulations of both the polymer systems studied were used to provide insight into the molecular background of transition state stabilisation, and differences in properties of the systems based on different cross-linkers.
Abstract: The present review has sought to explore the technological advances that have been made in recent years towards the selective analysis of uric acid and critically evaluate how they could, in fact, be exploited as a basis for a multi analyte sensor incorporating uric acid detection. Numerous strategies have evolved in recent years but these have invariably focused on the manufacture and response characterization of discrete sensors. Various methods of obtaining selective detection such as use of uricase enzymes, nanoparticles, carbon nanotubes, polymers, conducting polymers and MIPs are also discussed along with the clinical relevance of UA determination.
Abstract: The detection of specific proteins as biomarkers of disease, health status, environmental monitoring, food quality, control of fermenters and civil defence purposes means that biosensors for these targets will become increasingly more important. Among the technologies used for building specific recognition properties, molecularly imprinted polymers (MIPs) are attracting much attention. In this critical review we describe many methods used for imprinting recognition for protein targets in polymers and their incorporation with a number of transducer platforms with the aim of identifying the most promising approaches for the preparation of MIP-based protein sensors (277 references)
Abstract: A novel compound N-(N',N'-diethyldithiocarbamoylethylamidoethyl)aniline (NDDEAEA) was synthesized and fully characterized. Conjugated poly(NDDEAEA), consisting of N-substituted polyaniline (PANI) backbones with dithiocarbamate ester pendant groups (which can act as iniferters), was synthesized by both chemical and electrochemical polymerization. UV-initiated living polymerization was utilized to graft styrene, methacrylic acid (MAA), lauryl methacrylate, and acrylamido-2-methylpropanesulfonic acid (AMPSA) onto the conjugated macroiniferter which had previously been deposited on various surfaces (glass, polypropylene, polystyrene, and gold electrodes). The resultant polymeric surfaces were characterized by static contact angle measurements, XPS, SEM, and AFM. This versatile new material can be used for creating materials with integrated functionalities (e.g., conductivity, molecular recognition, catalysis and controlled transport properties, etc.) for application in sensors and microfluidic devices and for the construction of patterned surfaces.
Abstract: Growing good-quality single crystals of proteins for high-resolution X-ray diffraction relies on the use of a diverse range of materials as nucleating agents. Smart hydrogels, in the form of molecularly imprinted polymers, may provide a general solution.
Abstract: Cross on UV light: A polymer bearing dithiocarbamate ester groups, linked to the polymer backbone through the dithiocarbamate nitrogen atom is capable of reversible cross-linking and de-linking through photochemical rearrangement of the pendant groups (see scheme)
Abstract: Recent advances in nanotechnology have allowed significant progress in utilising cutting-edge techniques associated with nanomaterials and nano-fabrication to expand the scope and capability of biosensors to a new level of novelty and functionality. The aim of this work was the development and characterisation of conductive polyaniline (PANI) nanostructures for applications in electrochemical biosensing. We explore a simple, inexpensive and fast route to grow PANI nanotubes, arranged in an ordered structure directly on an electrode surface, by electrochemical polymerisation using alumina nanoporous membranes as a 'nano-mould'. The deposited nanostructures have been characterised electrochemically and morphologically prior to grafting with a molecularly imprinted polymer (MIP) receptor in order to create a model sensor for catechol detection. In this way, PANI nanostructures resulted in a conductive nanowire system which allowed direct electrical connection between the electrode and the synthetic receptor (MIP). To our knowledge, this is the first example of integration between molecularly imprinted polymers and PANI nanostructured electrodes. The advantages of using nanostructures in this particular biosensing application have been evaluated by comparing the analytical performance of the sensor with an analogous non-nanostructured MIP-sensor for catechol detection that was previously developed. A significantly lower limit of detection for catechol has been obtained (29 nM, one order of magnitude), thus demonstrating that the nanostructures are capable of improving the analytical performance of the sensor
Abstract: A âgrafting fromâ approach has been used for controlled deposition of cross-linked polymers by living radical polymerisation. Borosilicate glass was modified with N,Ndiethylaminodithiocarbamoylpropyl( trimethoxy)silane, in order to confine the iniferter reactive groups solely at its surface, then placed in solution with monomers and cross-linker. The polymerisation was initiated by UV irradiation. Formation of the cross-linked polymers was studied in terms of time course of the reaction, type of monomers incorporated and influence of oxygen. Grafted surfaces were characterised by AFM, FT-IR, ellipsometry and contact angle measurements. The ability to control the grafted layer improved dramatically when the chain terminator agent, N,N,N' ,N'-tetraethyl thiuram disulphide (TED) was added. Upon irradiation TED increases the concentration of passive capping radicals and decreases the possibility of recombination of active macro-radicals, thus prolonging their lifetime. In the absence of TED the thickness of produced coatings was below 10 nm. TED added at different concentrations assisted in the formation of grafted layers of 10â130nm thickness. Iniferter chemistry in the presence of TED can be used for growing nanometre-scale polymer layers on solid supports. It constitutes a robust general platform for controlled grafting and offer a general solution to address the needs of surface derivatisation in sensors technology.
Abstract: A first attempt to attenuate the quorum sensing (QS) of a marine heterotroph microorganism, Vibrio fischeri,
using signal molecule-sequestering polymers (SSPs) is presented. A set of rationally designed polymers with
affinity toward a signal molecule of V. fischeri, N-(beta-ketocaproyl)-L-homoserine lactone (3-oxo-C6-AHL) was
produced. It is reported that computationally designed polymers could sequester a signal molecule of V. fischeri
and prevent QS-controlled phenotypes (in this case, bioluminescence) from being up-regulated. It was proven
that the attenuation of bioluminescence of V. fischeri was due to sequestration of the signal molecule by specific
polymers and not due to the toxicity of polymer or nonspecific depletion of nutrients. The ability to disrupt the
bacterial communication using easy to synthesize and chemically inert polymers could provide a new concept for
the development of pharmaceuticals and susceptible device coatings such as catheters.
Abstract: Soluble molecularly imprinted nanoparticles were synthesised via iniferter initiated polymerisation and separated by size via gel permeation chromatography. Subsequent fractionation of these particles by affinity chromatography allowed the separation of high affinity fractions from the mixture of nanoparticles. Fractions selected this way possess affinity similar to that of natural antibodies (Kd 6.6 x 10-8) M and were also able to discriminate between related functional analogues of the template.
Abstract: A series of synthetic polymers were designed and synthesized for enhancing the rate of the Diels-Alder cycloaddition reaction of 1,3-butadiene carbamic acid benzyl ester (1) and N,N-dimethyl acrylamide (2), to yield the corresponding endo- (3) and exo- (4) reaction products. Putative transition state analogues (TSAs) for the endo- (5) and exo- (6) reaction pathways were used as templates for the synthesis of molecularly imprinted methacrylic acid (MAA)âdivinylbenzene (DVB) copolymers. The polymer system utilized was selected based upon a series of 1H NMR studies of complex formation between template and a functional monomer analogue (Kd (app) â 70 mM, d8-toluene, 293 K). Batch binding studies revealed that the imprinted polymers were selective for the TSA corresponding to the template used in the polymer synthesis. Studies on the influence of the polymers on the catalysis of the reaction of 1 and 2 demonstrated a 20-fold enhancement of the rate of the reaction relative to the solution reaction. A surprising temperature dependence of the reaction of 1 and 2 in the presence of the polymers was observed, which provides support for the role of template-functional monomer complexes in the catalysis of the Diels-Alder reaction.
Abstract: One of the difficulties with using molecularly imprinted polymers (MIPs) and other electrically insulating materials as the recognition element in electrochemical sensors is the lack of a direct path for the conduction of electrons from the active sites to the electrode. We have sought to address this problem through the preparation and characterization of novel hybrid materials combining a catalytic MIP, capable of oxidizing the template, catechol, with an electrically conducting polymer. In this way a network of âmolecular wiresâ assists in the conduction of electrons from the active sites within the MIP to the electrode surface. This was made possible by the design of a new monomer that combines orthogonal polymerizable functionality; comprising an aniline group and a methacrylamide. Conducting films were prepared on the surface of electrodes (Au on glass) by electropolymerization of the aniline moiety. A layer of MIP was photochemically grafted over the polyaniline, via N,Nâ²-diethyldithiocarbamic acid benzyl ester (iniferter) activation of the methacrylamide groups. Detection of catechol by the hybrid-MIP sensor was found to be specific, and catechol oxidation was detected by cyclic voltammetry at the optimized operating conditions: potential range â0.6 V to +0.8 V (vs Ag/AgCl), scan rate 50 mV/s, PBS pH 7.4. The calibration curve for catechol was found to be linear to 144 μM, with a limit of detection of 228 nM. Catechol and dopamine were detected by the sensor, whereas analogues and potentially interfering compounds, including phenol, resorcinol, hydroquinone, serotonin, and ascorbic acid, had minimal effect (â¤3%) on the detection of either analyte. Non-imprinted hybrid electrodes and bare gold electrodes failed to give any response to catechol at concentrations below 0.5 mM. Finally, the catalytic properties of the sensor were characterized by chronoamperometry and were found to be consistent with MichaelisâMenten kinetics.
Abstract: An approach has been developed for the grafting of monomers onto poly(trimethylolpropane trimethacrylate) (polyTRIM) particles using 2,2-diethyl dithiocarbamic acid benzyl ester (DDCABE) as an initiator. A set of polymers was prepared with this technique over different lengths of time and the kinetics of the reaction studied experimentally. It was found that the grafting of initiator to the polymeric support followed a second order reaction, while the subsequent addition of monomers from solution into the polyTRIM macroradicals followed a first order reaction. The living nature of the iniferter modified macroradicals permits easy consecutive grafting of multiple polymeric layers, allowing straightforward functionalisation of particles. However, the effectiveness of the grafted initiator decreased with each cycle of polymerisation. This technique can be used for a wide range of applications in analytical and biochemistry.
Abstract: A new monomer, which incorporates both aniline and methacrylamide functional groups, was shown to possess orthogonal polymerisation behaviour to produce conjugated polyaniline suitable for a wide range of applications.
Abstract: Immobilisation of biorecognition elements on transducer surfaces is a key step in the development of biosensors. The immobilisation needs to be fast, cheap and most importantly should not affect the biorecognition activity of the immobilised receptor. A novel protocol for the covalent immobilisation of biomolecules containing primary amines using an inexpensive and simple polymer is presented. This tri-dimensional (3D) network leads to a random immobilisation of antibodies on the polymer and ensures the availability of a high percentage of antibody binding sites. The reactivity of the polymer is based on the reaction between primary amines and thioacetal groups included in the polymer network. These functional groups (thioacetal) do not need any further activation in order to react with proteins, making it attractive for sensor fabrication. The novel polymer also contains thiol derivative groups (disulphide groups or thioethers) that promote self-assembling on a metal transducer surface. For demonstration purposes the polymer was immobilised on Au Biacore chips. The resulting polymer layer was characterised using contact angle meter, atomic force microscopy (AFM) and ellipsometry. A general protocol suitable for the immobilisation of bovine serum albumin (BSA), enzymes and antibodies such as polyclonal anti-microcystin-LR antibody and monoclonal anti-prostate specific antigen (anti-PSA) antibody was then optimised. The affinity characteristics of developed immunosensors were investigated in reaction with microcystin-LR, and PSA. The calculated detection limit for analytes depended on the properties of antibodies. The detection limit for microcystin-LR was 10ángámL-1 and for PSA 0.01ángámL-1. The non-specific binding of analytes to synthesised polymers was very low. The polymer-coated chips were stored for up to 2 months without any noticeable deterioration in their ability to react with proteins. These findings make this new polymer very promising for the development of low-cost, easy to prepare and sensitive biosensors
Abstract: Traditionally, the integration of sensing gel layers in surface plasmon resonance (SPR) is achieved via "bulk" methods, such as precipitation, spin-coating or in-situ polymerization onto the total surface of the sensor chip, combined with covalent attachment of the antibody or receptor to the gel surface. This is wasteful in terms of materials as the sensing only occurs at the point of resonance interrogated by the laser. By isolating the sensing materials (antibodies, enzymes, aptamers, polymers, MIPs, etc.) to this exact spot a more efficient use of these recognition elements will be achieved. Here we present a method for the in-situ formation of polymers, using the energy of the evanescent wave field on the surface of an SPR device, specifically localized at the point of interrogation. Using the photo-initiator couple of methylene blue (sensitizing dye) and sodium p-toluenesulfinate (reducing agent) we polymerized a mixture of N,N-methylene-bis-acrylamide and methacrylic acid in water at the focal point of SPR. No polymerization was seen in solution or at any other sites on the sensor surface. Varying parameters such as monomer concentration and exposure time allowed precise control over the polymer thickness (from 20-200ánm). Standard coupling with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide was used for the immobilization of protein G which was used to bind IgG in a typical biosensor format. This model system demonstrated the characteristic performance for this type of immunosensor, validating our deposition method
Abstract: Although molecular imprinting in organic polymers was introduced by Wulff more than 30 years ago,(1) this promising technology has yet to realize its full commercial potential, partially due to the lack of a clear understanding of how physical factors affect the polymerization process and what basic rules should be applied in order to produce synthetic receptors with the required characteristics. This arises mainly from the complex nature of the polymerization reaction in cross-linked systems which depends on many interrelated factors. Among the most important physical factors affecting the polymerization process, as well as the recognition properties of the materials produced, are temperature, type of initiation, pressure, magnetic field, volume of the polymerization mixture, dielectric constants of monomers and solvent, and polymerization time. This paper was inspired by the urgent need to summarize the knowledge generated concerning how polymerization conditions affect the quality of molecularly imprinted polymers (MIPs) in order to help the imprinting community make rational and effective choices and maximize their chances for success.
Abstract: In molecularly imprinted polymers (MIPs) a high level of cross-linking is usually important for preserving the receptor structure. We propose here an alternative approach for stabilising binding sites, which involves the use of an immobilised template. The idea is based on the assumption that an immobilised template will hold polymeric chains and complementary functionalities together, preventing the collapsing of the binding sites. To test this postulate, a range of polymers was prepared using polymerisable (2,4-diamino-6-(methacryloyloxy)ethyl-1,3,5-triazine) and non-polymerisable (or extractable) (2,4-diamino-6-methyl-1,3,5-triazine) templates, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linker. The level of cross-linking was varied from 12 to 80%. Polymerisations were performed in acetonitrile using UV initiation. Binding properties of the synthesised materials were characterised both by HPLC and equilibrium batch binding experiments followed by HPLC-MS or UV-visible detection. The adsorption isotherms of polymers were obtained and fitted to the Langmuir model to calculate dissociation constant, Kd, and concentration of binding sites for each material. The results strongly indicate that the presence of an immobilised template improves the affinity of MIPs containing low percentages of cross-linker. The low cross-linked MIPs synthesised with a polymerisable template also retain a reasonable degree of selectivity. Low cross-linked MIPs with such binding characteristics would be useful for the creation of new types of optical and electrochemical sensors, where induced fit or the gate effect could be used more effectively for generating and enhancing sensor signals.
Abstract: Objectives: Alkylating agents are potentially genotoxic impurities that may be present in drug products. These impurities occur in pharmaceuticals as by-products from the synthetic steps involved in drug production, as impurities in starting materials or from in-situ reactions that take place in the final drug product. Currently, analysis for genotoxic impurities is typically carried out using either HPLC/MS or GC/MS. These techniques require specialist expertise, have long analysis times and often use sample clean-up procedures. Reichardt's dye is well known for its solvatochromic properties. In this paper the dye's ability to undergo alkylation is reported. Methods: The reaction between Reichardt's dye and alkylating agents such as 4-chloro-1-butanol and ethyl methanesulfonate was monitored spectrophotometrically at 618 nm in acetonitrile and 624 nm in N,N-dimethylformamide. Key findings: Changes in absorption were observed using low levels of alkylating agent (5-10 parts per million). Alkylation of the dye with 4-chloro-1-butanol and ethyl methanesulfonate was confirmed. Reichardt's dye, and its changing UV absorption, was examined in the presence of paracetamol (10 and 100 mg/ml). Whilst the alkylation-induced changes in UV absorption were not as pronounced as with standard solutions, detection of alkylation was still possible. Conclusions: Using standard solutions and in the presence of a drug matrix, Reichardt's dye shows promise as a reagent for detection of low levels of industrially important alkylating agents.
Abstract: A new solid-phase extraction (SPE) matrix with high affinity for the neurotoxin domoic acid (DA) was designed and tested. A computational modelling study led to the selection of 2-(trifluoromethyl)acrylic acid (TFMAA) as a functional monomer capable of imparting affinity towards domoic acid. Polymeric adsorbents containing TFMAA were synthesised and tested in high ionic strength solutions such as urine and seawater. The TFMAA-based polymers demonstrated excellent performance in solid-phase extraction of domoic acid, retaining the toxin while salts and other interfering compounds such as aspartic and glutamic acids were removed by washing and selective elution. It was shown that the TFMAA-based polymer provided the level of purification of domoic acid from urine and seawater acceptable for its quantification by high performance liquid chromatography-mass spectrometry (HPLC-MS) and enzyme-linked immunosorbent assay (ELISA) without any additional pre-concentration and purification steps
Abstract: An entirely new means of printing molecular information on a planar film, involving casting nanoscale impressions of the template protein molecules in molten gallium, is presented here for the first time. The metallic imprints not only replicate the shape and size of the proteins used as template. They also show specific binding for the template species. Such a simple approach to the creation of antibody-like properties in metallic mirrors can lead to applications in separations, microfluidic devices, and the development of new optical and electronic sensors, and will be of interest to chemists, materials scientists, analytical specialists, and electronic engineers
Abstract: The effect of cross-linkers ethyleneglycol dimethacrylate (EGDM) and divinylbenzene (DVB) on the recognition properties of cholesterol-imprinted polymers, prepared by the sacrificial spacer method, was investigated. As reported previously EGDM-based polymers selectively bound cholesterol in preference to cholest-5-ene-3-one. The addition of up to 30% DVB led to an increase in the binding capacity with very little trade-off in selectivity. However polymers prepared with pure DVB, or DVB/styrene showed complete reversal of selectivity, in some cases binding cholest-5-ene-3-one to the exclusion of cholesterol from a solution containing both ligands. An explanation based on template conformation has been proposed to account for these observations
Abstract: The use of molecularly imprinted polymers (MIPs) in chemical and bioanalytical applications has been gaining in interest in recent years. Compared to their biological receptor counterparts, MIPs are easy to prepare, have long shelf stability and can be used under a variety of harsh conditions. The majority of MIPs currently used are produced by traditional free radical polymerization. One drawback with the use of standard free radical initiators is that little control can be exerted over the chemical processes that form the final imprinted cavities. In this study we set out to investigate the application of controlled (living) free radical polymerization to the preparation of MIPs. This was exemplified by the synthesis of cholesterol-imprinted bulk polymers by nitroxide-mediated polymerization (NMP). A sacrificial covalent bond was employed to maintain imprinting fidelity at elevated temperature. Selective uptake of cholesterol from solutions in hexane was studied with imprinted polymers prepared under different conditions. The imprinted hydrolyzed MIP prepared by NMP displayed higher selective cholesterol binding than that prepared by a traditional radical polymerization
Abstract: The saturated oxygen concentration in a series of aqueous solutions of sorbitol (up to 35% w/w) and maltitol (up to 50% w/w) was measured using colorimetric reagent vials based on Rhodazine D. The results indicate that the solubility of oxygen in low-water carbohydrates is considerably lower than its solubility in pure water. It was concluded that the low-oxygen solubility is a major factor contributing to the barrier properties of low-water content carbohydrates used in the encapsulation of flavours, lipids, peptides and other oxidisable species. (c) 2005 Elsevier Ltd. All rights reserved
Abstract: A two step non-competitive affinity method for the trace determination of 1-hydroxypyrene (1-OHP) using a disposable molecularly imprinted polymer (MIP) modified screen-printed carbon electrode (MIP-SPCE) has been developed. The MIP was synthesized according to a novel strategy, which is described, and is capable of rebinding the phenolic analyte, 1-hydroxypyrene (1-OHP), from high pH aqueous organic media, via ionic interactions. In the first step of our method 1-OHP was accumulated at the MIP-SPCE from 35% aqueous methanol containing 0.014 M NaOH and 0.14 M NaCl, at open circuit. In the second step, the resulting SPCE with accumulated 1-OHP was then transferred to fresh, clean phosphate buffered aqueous methanol, and subjected to cyclic voltammetry (CV) or differential pulse voltammetry (DPV). The latter technique proved to be more sensitive at detecting 1-OHP, with a limit of detection of 182 nM and a linear range to 125 mu M on unmodified electrodes. The possible effects of interference by related phenolic compounds in the MIP-SPCE of I-OHP were investigated. Finally the method was evaluated by carrying out 1-OHP determinations on spiked human urine samples; the recovery of 1-OHP was 79.4% and the coefficient of variation was found to be 7.7% (n=4) using a separate MIP-SPCE for each determination. Therefore, the performance data suggests that the method is reliable at the concentrations examined in this study. The method was found to be superior to the direct determination of 1-OHP in human urine by DPV alone, which was greatly affected by interference from uric acid
Abstract: To test whether the extent of physical aging affected the reaction rate, Maillard reaction kinetics were studied in glassy model preservation systems subjected to two different thermal histories. The glass transition temperature and physical aging of the matrix were determined using differential scanning calorimetry, and the normalized heat capacities were modeled using the Tool-Narayana-swamy- Moynihan approach. Samples prepared using the different thermal histories initially had different degrees of aging, but these were practically indistinguishable after 10 h under the reaction conditions (65 degrees C); the samples underwent rapid structural relaxation at that temperature. The reaction of glucose and lysine in an amorphous trehalose/sucrose matrix was followed using spectrophotometric and chromatographic analysis. A difference in reaction rate could only be distinguished in the rate of consumption of glucose, which was approximately 20% faster in the minimally aged matrix; no significant differences were seen in any other indicator of reaction
Abstract: Molecular imprinting is a method of inducing molecular recognition properties in synthetic polymers in response to the presence of a template species during formation of the three-dimensional structure of the polymer. The molecularly imprinted polymers (MIPs) prepared in this way have been termed "plastic antibodies" and combine the robustness of the polymer scaffold with binding properties more readily associated with biological receptors. Smart polymers of this type may find applications in drug delivery, controlled release and monitoring of drug and metabolite concentrations. In this review the main synthetic strategies used in the preparation of imprinted organic polymers are described in terms of the chemical principles used in the templating step. These are illustrated with examples taken from the literature and are classified as covalent, semi-covalent, non-covalent, metal-mediated and non-polar. Finally strategies for the selection of monomers, optimisation and modification of the properties of imprinted polymers are reviewed
Abstract: A comparison of three different methods for the imprinting of small aromatic heterocycles containing only a single nitrogen atom, for the preparation of specific analytical phases, was carried out. A conventional non-covalent approach to the imprinting of pyridine using methacrylic acid as the functional monomer was compared with two sacrificial spacer methods, in which heterocycles were imprinted as covalent template analogues. The results of binding experiments showed that discrimination based on ligand size was possible when polymers were prepared using a silyl ester-based template. The most selective polymer was able to bind pyridine in preference to quinoline or acridine which is opposite to the trend predicted by the pK(HB) values for the three ligands. Curve fitting of the isotherm for pyridine binding to this polymer to the Langmuir model gave an approximate K-d of 1.1 +/- 0.1 mM and a binding site concentration of 57 +/- 2 mmol g(-1). Acridine binding did not show saturation behaviour and was non-specific and cooperative in nature. (C) 2003 Elsevier Science B.V.. All rights reserved
Abstract: A molecularly imprinted polymer specific for the mycotoxin ochratoxin A has been synthesised using a non-covalent approach. The polymer has shown an excellent affinity and specificity for the target template in aqueous solutions. The binding experiments, NMR study and molecular modelling have proven that the template recognition by polymer originates from the shape complementarity of binding sites. The binding mechanism is critically depended on factors that affect the polymer conformation. Thus the variation in buffer concentration, pH and presence of organic solvent, which affect the polymer swelling or shrinking, had a profound effect on the polymer recognition properties. (C) 2004 Elsevier B.V. All rights reserved
Abstract: Poly(methyl methaerylate/2-methaeryloyletkyl methacrylate)-based copolymers of varying composition have been synthesized and characterized, Free-radical polymerization of hydroxyethyl methacrylate and methyl methaerylate over a range of monomer feed ratios gives an ideal random copolymer series which has been functionalized by further methaeryloylation of the pendant hydroxyl group. The resulting polymers have been cross-linked both thermally and by UV exposure, as evidenced by infrared and solid-state NMR spectroscopy. After thermal cross-linking the polymers remain stable up to 200 degreesC. Variation of polymer composition has allowed the refractive index to be tuned between 1.497 and 1.518, a range suitable for waveguide applications, and channel waveguides have been fabricated by UV writing. The propagation loss of these channel waveguides is less than 1 dB/cm at a range of near-IR wavelengths
Abstract: Imprinted polymers were prepared from divinylbenzene and 6-methacrylamidohexanoic acid as the functional monomer, using calcite crystals of three different morphologies as templates. After template removal voids in the polymer remained which reflected the size and shape of the template crystals. The use of these imprinted polymers in aqueous supersaturated calcium carbonate solution resulted in the formation of some crystal objects of unusual morphology. In the case of spheroidal imprints, the nucleated crystals grow via the {104} faces in many directions creating clusters whose surface consists of many small rhombohedral crystallites. However, in the case of rhombohedral imprints, no conflict between crystal growth and the constraints of nucleation at the polymer surface arises and the new crystals very closely resemble the templates. (C) 2001 Society of Chemical Industry
Abstract: A novel approach to the potential desulphurisation of fuels such as diesel is proposed. It relies on the creation of recognition sites complementary to sulphur-containing compounds in highly cross-linked polymeric matrices using the molecular imprinting technique. Dibenzothiophene sulphone (DBTS) was used as template for the preparation of molecularly imprinted polymers (MIPs). Four different polymers were synthesised using 5-octyloxy-1,3-bis(4-ethenylphenyl)-benzenedicarboxamide or methacrylic acid and divinylbenzenes or ethylene glycol dimethacrylate as functional monomers and cross-linkers, respectively. Three polymers showed better binding of DBTS than non-imprinted controls, and were also superior in adsorption of organosulphur compounds such as dibenzothiophene (DBT) and benzothiophene (BT) present in a model mixture. A maximum adsorption of 66 mg DBT per gram of polymer was observed at a polymer load of 10 gl(-1) and an initial DBT concentration of 3.69 gl(-1). The polymers also showed selectivity for fluorene. (C) 2001 Elsevier Science B.V. All rights reserved
Abstract: Imprinted polymers (see Figure) find applications in chemistry, biotechnology, food technology and materials science. Here the current trends in imprinted polymers and the methods used in their preparation are reviewed, leading to a discussion of examples of applications, such as separation media, analytical systems, sensors, and catalysts. [GRAPHICS]
Abstract: Submicrometer surface-imprinted particles were prepared by a two-stage aqueous emulsion polymerization with a poly(divinylbenzene) shell over a cross-linked poly(styrene) core. The second stage polymerization was performed in the presence of a polymerizable surfactant (pyridinium 12-(4-vinylbenzyloxycarbonyl)dodecanesulfate, PS) and pyridinium 12-(cholesteryloxycarbonyloxy)dodecanesulfate (TS), which acted both as a surfactant and as a template. Removal of the template left hydrophobic cavities on the surface of charged particles or particles bearing benzyl alcohol groups, dependent on the protocol adopted. Particles were shown to rebind cholesterol in 60% a-propanol in water, and a poly(ethylene glycol) (PEG) modified with cholesterol at both chain ends was capable of flocculating the imprinted particles. No flocculation was seen either when a monocholesteryl PEG was used or when nonimprinted particles were used
Abstract: Submicron core-shell polymer particles, with molecularly imprinted shells, were prepared by a two-stage polymerization process. Particles of this type, prepared with a cholesterol-imprinted ethyleneglycol dimethacrylate shell and in the absence of porogen, were found to be 76 nm in diameter with a surface area of 82 m(2) g(-1) Cholesterol uptake from a 1 mM solution in isohexane was measured at both 10 and 30 mg mL(-1), with the imprinted polymer showing considerable binding (up to 57%). Imprinted but not hydrolyzed and hydrolyzed nonimprinted polymers showed very low uptakes (less than or equal to 4.5%) and a phenol-imprinted polymer showed reduced binding (36%) under the same conditions. Imprinted shells were also prepared over superparamagnetic polymer cores and over magnetite ferrocolloid alone. The cholesterol binding to magnetic particles was very similar to that of equivalent nonmagnetic materials. Magnetic particles could be sedimented in as little as 30 s in a magnetic field. (C) 2000 John Wiley & Sons, Inc
Abstract: The use of molecularly imprinted polymers in synthetic organic chemistry is reviewed. These materials are prepared in the presence of a template for which they carry a functional and stereochemical "memory" and can be likened to artificial antibodies or enzymes. Their unique properties have been exploited by the use of imprinted polymers as stereo- and regio-selective solid supports in condensation reactions and hydride reduction, as protecting groups in the acylation of polyols and as catalysts to enhance the rates of reactions as diverse a Diels-Alder reaction, an Aldol condensation, beta-elimination, the benzisoxazole isomerization, transesterification and ester hydrolyses
Abstract: Imprinted polymers were synthesized for the recognition of small nitrogen heterocycles such as pyridine and quinoline using a new variant of the sacrificial spacer methodology employing silyl ether derivatized templates designed to act as N-H-O 'isosteres' for binding the targets. The cleavage of the labile silyl ether bond led to the formation of sites bearing phenolic residues. The polymers prepared with DVB as the cross-linker were capable of discriminating between pyridine, quinoline and acridine in hexane but the effect did not exceed 20%. In order to improve the recognition properties of these materials, a post-imprinting modification of the polymers was performed using acyl chlorides of varying size. This simple approach, carried out after the removal of the templates, resulted in an enhanced selectivity (by factors of up to 5-fold) for binding of pyridine and quinoline by the modified polymers. Similar effects were observed with EGDMA-based imprinted polymers. The results obtained suggest that post-imprinting chemical modification can be an effective tool to engender 'size' selectivity in binding of even small molecules containing a paucity of functional groups. (C) 2000 Elsevier Science Ltd. All rights reserved
Abstract: The feasibility of preparing cholesterol-imprinted polymers by aqueous suspension polymerization was investigated by the preparation of ethyleneglycol dimethacrylate and divinylbenzene-based beads imprinted using cholesteryl(4-vinyl)-phenyl carbonate as the template. A low volatility porogen to replace a 4:1 hexane/ toluene mixture was selected on the basis of solubility parameters and consisted of dioctyl phthalate/n-decane 77:23 v/v. Beads were prepared using a range of porogen contents with the best results obtained at 5.5-6.5 mL /5 g of monomer. Uptake of cholesterol by suspension polymers was broadly similar to that of the corresponding "bulk" polymers, but suffered from higher nonspecific binding. (C) 2000 John Wiley & Sons, Inc
Abstract: Two new functional monomers for molecular imprinting, 5-(4"'-vinyl)benzyloxy-1,3-bis[2'(3 ",3 ",4 ",4 "-tetramethyl-2 ",5 "-dioxaborolanyl)phenylcarbomoyl]benzene (3) and 2-(4-vinylphenyloxy)-3,5,6-trichlorobenzoquinone (4), designed to interact with carboxylate and amino groups, respectively, were synthesized. NMR titrations confirmed the interactions of 3 with tertabutylammonium acetate and ampicillin carboxylate in d(6)-DMSO and of 4 with the free amino group of ampicillin in the same solvent. Polymers mere prepared, using DMSO or THF as porogen, imprinted with ampicillin carboxylate using 3 and 4 present in the polymerization mixture in only stoichiometric amounts. The polymer made in DMSO was shown to bind ampicillin from aqueous buffer at pH 8.0 with two populations of binding sites, the first characterized by K-d = (3.0 +/- 0.3) x 10(-5) mol/L at a capacity of 5.8 +/- 0.3 mu mol/g and the second by K-d = (9.6 +/- 1.1) x 10(-4) mol/L and 48 +/- 3.4 mu mol/g
Abstract: Imprinted polymers were synthesized using a mixture of pigments, N-glutamyl-rubropuctamine, and N-glutamyl-monascorubramine (I) as the template, and 2-methacrylamido-6-picoline or 4-aminostyrene as functional monomers, to obtain recognition materials capable of forming hydrogen bonds and charge interactions, respectively, with carboxyl groups of target I in the binding sites. The polymers were prepared thermally at a template loading of 5 mol% using ethylene-glycol dimethacrylate or trimethylolpropane trimethacrylate as crosslinkers and acetonitrile or tetrahydrofuran as porogens. The selective binding of I to both types of polymer was demonstrated, although aminostyrene-based materials showed higher overall adsorption and were studied in more detail. It was shown that the kinetics of binding of I from ethyl-acetate extracts of fermented Monascus sp. was very rapid and virtually all the pigment adsorbed can be released by washing the polymer with ethanol-water mixtures. The feasibility of reusing im printed polymer in consecutive adsorption/desorption cycles was also demonstrated. (C) 1999 John Wiley & Sons, Inc
Abstract: A new approach to the preparation of dimeric (gemini) and trimeric sugar fatty acid esters has been developed. It was shown that immobilized Candida antarctica lipase (Novozyme) readily catalyzes acylation of 1,2:3,4-di-O-isopropylidene-D-galactopyrose and methyl-alpha-D-glucopyranoside with 2-bromomyristic acid, with the reaction rate being about three times slower than that observed with myristic acid. However, virtually no product was detected after incubating this enzyme with 2-bromomyristic acid and 4-O-(3',4'-O-isopropylidene-beta-D-galactopyranosyl)-2,3 :5,6-di- O-isopropylidene-1,1-di-O-methyl-D-glucose (lactose tetra-acetal) for 3 days. On the contrary, Mucor miehei lipase (Lipozyme) catalyzed the formation of 6'-O-(2-bromomyristoyl)-4-O-(3',4'-O-isopropylidene-beta-D-galactopyrano syl)-2,3:5,6-di-O-isopropylidene-1,1-di-O-methyl-D-glucose at preparatively useful rates, although it was found to be inferior to Novozyme in the acylation of the monosaccharide-based substrates. The products obtained after enzymatic transformation were chemically dimerised with dicarboxylic acids, and after deprotection, in the case of 1,2:3,4-di-O-isopropylidene-D-galactopyranose and lactose tetra-acetal esters, the desired gemini were obtained in reasonable overall yields. A trimeric sugar ester surfactant was prepared in a similar fashion in just one step by reacting 6-O-(2-bromomyristoyl) methyl-alpha-D-glucoside with 1,3,5-tris (4-carboxybutyloxy) benzene. (C) 1999 Elsevier Science Inc. All rights reserved
Abstract: A simple and flexible chemoenzymatic route for the preparation of a wide range of dimeric (gemini) and trimeric mono- and disaccharide-based surfactants was developed. The synthesis relies on the use of enzymes for regioselective introduction of fatty acids into carbohydrate moieties. Several structures were prepared containing xylose, glucose, galactose, and lactose, connected via different hydroxyl groups in the sugar molecules or, alternatively, via the OH group of 2-hydroxytetradecanoic acid used as a hydrophobic moiety for the surfactant. Paper no. JSD1096 in JSD 2, 293-302 (July 1999)
Abstract: The finely tuned properties of natural biominerals and composites reflect the remarkable level of control that is exercised over the size, shape and organization of the constituent crystals(1-4). Achieving this degree of control over synthetic materials might therefore lead to superior material properties. Organic small molecules, polymers or surfactant mesophases have been used to guide the growth and morphology of inorganic materials via steric constraints or structure-directing interactions(5-16). Here we show that synthetic polymers can be imprinted with motifs of crystal surfaces so as to template the growth of specific crystal phases. Our polymers, imprinted with calcite, are able to induce the nucleation of calcite under conditions favouring the growth of aragonite (another polymorph of calcium carbonate). The synthesis of the polymers, based on the principles of molecular imprinting(17-20), involves the adsorption of functional monomers to a calcite surface, followed by co-polymerization with a cross-linker to create an imprint of the crystal surface. Subsequent removal of the calcite template yields a polymer matrix with a surface functionality mirroring the crystal face and able to promote the nucleation of calcite. We expect that the molecular-imprinting approach to directed nucleation can be applied to crystals other than calcite
Abstract: Polymeric receptors prepared by a combination of covalent and noncovalent imprinting show high selectivity for the amino acid sequence of the template (see schematic representation of the binding of the tripeptide Lys-Trp-Asp).
Abstract: Imprinted polymers were prepared using a functional monomer derived from boronophthalide and a number of steroid templates bearing spatially separated hydroxyl groups. The cooperative nature of the binding interaction was demonstrated in polymers imprinted with androst-5-ene-3 beta,17 beta-diol and its structural analogues. The stoichiometry and kinetics of binding were probed using LR spectroscopy, selective solvent extractions, and chemical modification experiments. The feasibility of using imprinted polymers as reusable protecting groups was established by the regioselective acylation of trihydroxysteroids bound to polymers imprinted with structurally related diols. In polymers prepared with tert-butyl ester templates "matched" to the substrate, regioselectivities as high as 23.1:1 (24-acetate:3-acetate) in the monoester products (65% of recovered material) were seen. In the "unmatched" case, the ratio fell to 5.4:1; however, in functionally identical control polymers, imprinted with ethylene glycol, the regioselectivity was completely reversed (< 1:100), and only poor yields of monoesters (13%) were obtained
Abstract: An aminostyrene-based polymer imprinted with glutamylated monascus pigments specifically bound the template but not other analogous pigments even when present in a mixture. The overall number of binding sites in the imprinted polymer and the equilibrium binding constant for the glutamylated pigment were determined as 0.023 mmol g(-1) polymer and 31 mM(-1) in ethylacetate, respectively
Abstract: Imprinted polymers as stationary phases for HPLC separations have been the subject of extensive investigations in recent years. In order to aid the rational design of synthetic protocols for the preparation of imprinted polymers, a series of calculations were made to assess the equilibrium concentration of template-monomer complexes as a function of association constant (K) for the functional groups involved in the interactions and initial concentrations of reactants. This data was then used to predict the selectivity of polymers prepared under different reaction conditions and the model was tested using an experimentally determined value of K and separation factors taken from the literature
Abstract: The aim of this investigation was to determine whether relatively weak interactions, such as hydrogen bonds to aromatic chlorine atoms and interactions involving aromatic pi electrons could be exploited within artificial receptors, constructed using the technique of molecular imprinting. For the purposes of this investigation we chose 2,3,7,8-tetrachlorodibenzodioxin (TCDD)as the model target. Imprinted polymers have been prepared with two new templates designed to create recognition sites for TCDD. The first of these, the bis-N-(4-vinylphenyl)urea derivative of 2,8-dichloro-3,7-diaminodibenzodioxin, employed a carbonyl spacer to introduce aromatic amines into the polymer after reductive cleavage of the template. The second, N-(2-(3,7,8-trichlorodibenzodioxinyl))-2-methacryloyloxybenzamide, incorporated a salicylic acid spacer and introduced a methacrylic acid residue into the polymer following hydrolysis. Both amine and acid groups were positioned in such a way as to interact with TCDD through the formation of weak hydrogen bonds to aromatic chlorine atoms. A second recognition element was introduced into the binding sites by the inclusion of a polymerizable, electron-rich, aromatic ether capable of forming pi-pi interactions with the electron-deficient dioxin molecule. Polymers imprinted with either template showed significantly higher uptake of TCDD than the corresponding nonimprinted controls, even at concentrations as low as 2 nM
Abstract: In molecular imprinting (MI), interactive monomers and suitable cross-linking agents are polymerized in the presence of a template. Once the template has been removed, the remaining space acts as a highly specific binding site for the template or analogs thereof, due to the unique three-dimensional arrangement of interaction points. Several steps are involved in producing such a polymer coat inside a capillary electrophoresis capillary. First, the silanization of the inner surface of the capillary with a suitable silane is necessary, to link a monolayer of unsaturated groups suitable for polymerization to the capillary surface. These monomeric groups are then integrated into the three-dimensional polymer coat produced in the next step, MI-capillary coatings ideally are highly porous and of a thickness, delta, which is smaller than the inner radius, r, of the capillary in question. Porous polymer networks can be produced by dispersive polymerization using a suitable solvent (porogen). However, the exact conditions for producing a coating suitable for capillary zone electrophoresis had to be determined experimentally. Seven porogens, namely hexane, toluene, tetrahydrofuran, acetonitrile, CHCl3, dimethyl sulfoxide and dimethylformamide, and two cross-linkers, namely ethyleneglycoldimethacrylate and divinylbenzene, at concentrations of between 5 and 20% (v/v) were investigated. In about 20% of the combinations, a polymer coat of the desired qualities was obtained, The applicability of the MI capillaries to specific separations was demonstrated for the separation of a racemic mixture of S(+)- and R(-)-2-phenylpropionic acid. trans-3-(3-Pyridyl)-acrylic acid was used as the interactive monomer in this case. (C) 1997 Elsevier Science B.V
Abstract: Molecular imprinting is an emerging technique for the introduction of recognition properties into synthetic polymers using suitable templates. Food industry applications of materials prepared by this technique include the selective removal of undesirable components, separations and analyses. Examples of each of these processes are presented along with a brief description of how imprinted polymers are made
Abstract: A novel approach to the introduction of recognition site functionality into highly cross-linked polymeric matrices via molecular imprinting has been developed for compounds with single (or multiple, spatially separated) hydroxyl groups. This new methodology relies on the use of the 4-vinylphenyl carbonate ester (1) which functions as a covalently bound template monomer but is easily and efficiently cleaved hydrolytically with the loss of CO2. This results in the formation of a noncovalent recognition site, bearing a phenolic residue, capable of interacting with the ligand (template) through hydrogen bonding. The polymers obtained by this method were shown to bind cholesterol with a single dissociation constant, thus displaying characteristics similar to a true biological receptor or synthetic host. It has also been shown that the phenolic residues introduced into the recognition site play an important role in the interaction with ligand, as evident from the suppression of cholesterol binding by chemical modification of the polymer with acetyl and benzoyl chlorides and by the addition of solvents which tend to disrupt hydrogen-bonding
Abstract: A series of methacrylate-based side-chain liquid crystal polymers has been prepared with a range of molecular weights. For the high molecular weight polymers a smectic phase is observed with a very narrow nematic range; however, for low molecular weight polymers only the nematic phase is observed. A marked reduction in the glass transition temperature, T(SN) and T(NI) is observed with a reduction in the molecular weight. The orientational order parameters for these polymers in the liquid crystal phase have been determined using infra-red dichroism. It is found that the higher the molecular weight of the polymer, the greater is the threshold voltage of the electro-optic response and the lower the order parameter. The increase in the threshold voltage with increasing molecular weight may be related to the intrinsic curvature elasticity and hence to the coupling between the mesogenic units and the polymer backbone
Abstract: The photo-Fries reaction of aryl esters provides a mechanism for the stimulation of a selective photoinduced structural rearrangement. We demonstrate that, in a side-chain liquid-crystal polymer containing 20% 4-methoxyphenyl cinnamate and 80% 4-cyanophenyl benzoate mesogens, photoinduced phase depressions may be achieved by selective irradiation of the cinnamate esters. When only the photo-Fries process is activated, by irradiation in dilute solution, subsequent phase depressions as high as 60-70-degrees-C are observed. In the liquid-crystalline state, other photoprocesses, including crosslinking, tend to predominate over the photo-Fries reaction and inhibit large-scale rearrangement, and hence rather limited phase transition shifts are observed
Abstract: The syntheses of three methacrylate monomers with cinnamate ester side-chains and of a further monomer with a corresponding cinnamide side-chain are described. Two of the monomers, with isomeric structures, were thermotropic liquid crystals. Although the clearing points were very similar the crystal melting points differed by 8-degrees-C. One compound also exhibited a monotropic smectic phase, behavior not shown by its isomer. The other two monomers were not liquid crystalline. The monomers were polymerized by free radical polymerization, both as homopolymers and as copolymers with methyl methacrylate. In the case of one of the mesogenic ester monomers, copolymers with a cyanophenyl benzoate monomer were also prepared. Three of the four monomers formed thermotropic liquid crystalline homopolymers and the copolymers with the benzoate monomer were also liquid crystalline. The monomers were considered as photoactive components of polymeric liquid crystals. As, a preliminary investigation of their photochemistry, copolymers with methyl methacrylate were prepared and irradiated in solution with a broad-band source. Under these conditions two of the materials show a facile photo-Fries rearrangement of the aryl cinnamate ester group
Abstract: A protecting group approach to the synthesis of a liquid crystalline polyacrylate containing a tetramethylene spacer unit is described. This approach prevents the formation of side products obtained when a more direct synthetic pathway is used. The resulting material shows behaviour typical of a nematic liquid crystal polymer
Abstract: The synthesis of methacrylate esters of 4-cyanophenyl-(4-(omega-hydroxyalkyloxy))cinnamates, with spacer lengths of 2 and 6 methylene units and the synthesis of the corresponding acrylate ester with a spacer of 2 methylene units are described. The methacrylate monomers were polymerized by free radical polymerization, both as homopolymers and as copolymers with the analogous benzoate monomer of spacer length 6. The acrylate ester could not be polymerized successfully under the same reaction conditions. Polymers were characterized by NMR spectroscopy, gel permeation chromatography, differential scanning calorimetry, and thermo-optic observations. Of the monomers prepared, only the cinnamate with a hexamethylene spacer shows a mesophase, seen on supercooling of the melt. All of the polymers prepared were liquid crystalline, with smectic behavior predominating in the polymethacrylates with the longer spacer group. A narrow nematic region is seen just below the clearing temperature with a range of 3-9-degrees-C, nematic character is increased in the copolymer series with the degree of incorporation of the cinnamate monomer with the spacer group of length 2
Abstract: A novel liquid-crystalline copolymer containing non-mesogenic cinnamate ester photoactive units is described. Selective irradiation of thin films of this polymer leads to an isothermal phase transition from the nematic to the isotropic phase arising from the photoinduced compositional changes involving E --> Z isomerisation. The potential of spatial control of this effect is demonstrated by irradiation through masks
Abstract: The synthesis of a series of aromatic poly(esteramide)s and the initial characterisation of these materials is reported in this paper. The polymers were prepared by transesterification polycondensation of various bis(p-alkyl benzoate) aliphatic diamides with diols of differing lengths. Most of the polymers gave multiple endothermic peaks during heating in the DSC, and polarising optical microscopy revealed a number of different types of spherulites. X-ray diffraction and infrared spectroscopy were used to probe the molecular correlations in the various crystalline phases. No evidence was found for liquid crystallisation.
Abstract: A series of chain liquid crystalline copolymers of 4-cyanophenyl 4-(6-methacryloyloxyhexyloxy)benzoate and 2-methacryloyloxyethyl -(1-naphthyl)-propenoate were prepared by free radical polymerization. The corresponding polyacrylates could not be prepared in the same way and an alternative method was used for their preparation involving the synthesis of copolymers of the mesogenic monomer and 2-hydroxyethyl acrylate followed by treatment of the resulting polymers with -(1-naphthyl)propenoyl chloride. The materials are of interest as photoactive liquid crystalline polymers. The effect of introducing a bulky nonmesogenic group into a liquid crystalline copolymer generally lowers the clearing temperature and raises Tg but also gives rise to contrasting phase behaviour in these two series of polymers. Polymethacrylates which show mesomorphism have sharp transitions and continue to exhibit a highly ordered smectic phase over the bulk of their liquid crystal range. Polyacrylates, on the other hand, exhibit a weakening and broadening-out of their thermal transitions consistent with a lowering of order. These results emphasize the effect of the polymer backbone on phase behaviour.
Abstract: In this work we explored a simple, cheap and fast route to grow polyaniline (PANI) nanotubes arranged in an ordered structure directly on an electrode surface by electrochemical polymerisation. The deposited nanostructures were electrochemically and morphologically characterised and then used as a functional substrate for biochemical sensing by combining the intrinsic advantages of nanostructures as optimal transducers and the well known benefits of molecularly imprinted polymers (MIPs) as receptors. The hybrid nanostructured-MIP sensor was applied to the molecular recognition of catechol. Moreover, a gas sensing application was also investigated by exploiting resistance variation of the polymer in presence of different gases (CO, NO 2 , NH 3 and ethanol)
