Olefin cross metathesis as a versatile method for the facile functionalization of porous polymers

Olefin cross metathesis has been employed for the first time for the postpolymerization chemical modification of porous polymers. High quality microspheres of poly(divinylbenzene) were synthesized by the precipitation polymerization of divinylbenzene-55 in porogenic solvents, and the olefin cross metathesis reactions of the pendent (polymer-bound) vinyl groups not consumed by polymerization were performed with diverse coupling partners in dichloromethane using the Grubbs 2 catalyst, leading to microspheres decorated with a wide range of functional groups

The synthesis and characterisation of porous and monodisperse, chemically modified hypercrosslinked poly(acrylonitrile)-based terpolymer as a sorbent for the adsorption of acidic pharmaceuticals

The synthesis and characterization of porous poly(acrylonitrile(AN)-co-divinylbenzene-80 (DVB-80)-co-vinylbenzylchloride (VBC)) polymers with high specific surface areas and weak anion-exchange character have been successfully researched. The hypercrosslinked (HXL) microspheres were chemically modified with 1,2-ethylenediamine (EDA) to enhance the adsorption selectivity of the HXL materials. The zeta potential of EDA-modified HXL poly(AN-co-DVB-80-co-VBC) revealed that the surface of the modified terpolymer was positively charged. The FT-IR spectra of the chemically modified hypercrosslinked poly(AN-co-DVB-80-co-VBC) showed that the nitrile groups derived from the AN unit were utilised by the presence of diamine groups. The BET-specific surface areas of the EDA-modified hypercrosslinked poly(AN-co-DVB-80-co-VBC) was 503 m2 g-1; meanwhile, the specific surface area of the HXL terpolymer was 983 m2 g-1. The adsorption isotherm data were well fitted by both the Langmuir and Freundlich models, whereas the adsorption kinetics followed the pseudo-second-order kinetic model. This study confirms that the EDA-modified hypercrosslinked poly(AN-co-DVB-80-co-VBC) terpolymer is a potential adsorbent for the adsorption of acidic pharmaceuticals

Facilitating serum determination of neuron-specific enolase at clinically relevant levels by coupling on-line molecularly imprinted solid-phase extraction to LC-MS/MS

The identification and quantification of biomarkers is essential for the diagnosis, treatment, and long-term monitoring of many human diseases. In the present work, macromolecular synthetic receptors with pre-determined affinity and selectivity for the signature peptide of a prognostically significant small cell lung cancer (SCLC) biomarker - neuron-specific enolase (NSE) – were prepared in a porous polymer microsphere format using a template-directed synthesis strategy performed under precipitation polymerization conditions. The polymer microspheres were packed into short trap columns and then exploited as molecularly selective sorbents in a fully automated, on-line molecularly imprinted solid-phase extraction (MISPE) protocol. The on-line MISPE protocol was optimised with respect to the composition of the loading mobile phase, the flow rate, and the extraction time. The molecularly imprinted polymers (MIPs) showed high affinity and useful selectivity for the peptide target - the hexapeptide ELPLYR - compared to non-imprinted control polymers. The MIPs were able to retain the biomarker on-column for extraction times of up to 20 min, and the on-line MISPE method enabled complete recovery of the biomarker over the linear range 10–100 ng mL−1 when the biomarker was present in spiked ammonium bicarbonate solution (R2 = 0.994). For extractions of ELPLYR from very complex biological matrices, the recoveries of ELPLYR from reversed-phase SPE (RP-SPE)-treated and untreated digested human serum were 100.8 ± 6.2% and 61.6 ± 1.9%, respectively. Extractions of ELPLYR from spiked untreated digested serum were linear in the range of 7.5–375 ng mL−1 (R2 = 0.99). The limit of detection (LOD) and limit of quantification (LOQ) for the biomarker in digested serum were estimated to be 1.8 ng mL−1 and 6.0 ng mL−1, respectively, which is below the median reference level of NSE in humans (8.6 ng mL−1). This work sets in place the basis for a new diagnostic tool for SCLC that is sensitive, robust, automated, and antibody-free, and which works very well with complex human plasma samples

Hypercrosslinked polymer microspheres decorated with anion- and cation-exchange groups for the simultaneous solid-phase extraction of acidic and basic analytes from environmental waters

Mixed-mode ion-exchange sorbents were introduced to improve the selectivity and retention of solid-phase extraction (SPE) sorbents,. Mixed-mode ion-exchange sorbents integrate reversed-phase chemistry with ion-exchange groups to promote favourable interactions with ionic species. Nevertheless, a need to extract analytes with acidic and basic properties simultaneously within the same SPE cartridge led to the introduction of novel amphoteric/zwitterionic sorbents, which incorporate cation- and anion-exchange moieties within the same functional group attached to the polymeric network. In the present study, the development, preparation and SPE evaluation of two novel hypercrosslinked zwitterionic polymeric sorbents, functionalised with either strong anion-exchange (SAX) and weak cation-exchange (WCX) or weak anion-exchange (WAX) and strong cation-exchange (SCX) groups (namely HXLPP-SAX/WCX and the HXLPP-WAX/SCX), is presented for the simultaneous retention of acidic and basic compounds. The sorbents were prepared by a precipitation polymerisation route which yielded poly(divinylbenzene-co-vinylbenzylchloride) as a precursor polymer; subsequently, the precursor polymer was hypercrosslinked, to increase the specific surface areas and capacities of the sorbents, and then functionalised to impart the zwitterionic character. The HXLPP-SAX/WCX sorbent was decorated with quaternised sarcosine groups and the HXLPP-WAX/SCX sorbent was decorated with taurine moieties. The SPE parameters were optimised to exploit the ionic interactions between compounds and the functional groups. The optimal conditions involve a washing step to remove the compounds retained by hydrophobic interactions, thus increasing the selectivity. The optimised SPE protocol used the quaternised sarcosine-based sorbent followed by liquid chromatography and tandem mass spectrometry, and was applied to determine compounds with acidic and basic properties from environmental samples, such as river water and effluent wastewater samples, with excellent selectivity and matrix effect values below -30% and apparent recovery results ranging from 52% to 105% for most of the compounds. The analytical method was validated for environmental water samples and used in the analysis of samples in which some of the target compounds were found at ng L−1 concentration levels

Microporous polymer microspheres with amphoteric character for the solid-phase extraction of acidic and basic analytes

Solid-phase extraction (SPE) is a widely-used and very well-established sample preparation technique for liquid samples. An area of on-going focus for innovation in this field concerns the development of new and improved SPE sorbents that can enhance the sensitivity and/or the selectivity of SPE processes. In this context, mixed-mode ion-exchange sorbents have been developed and commercialised, thereby allowing enhanced capacity and selectivity to be offered by one single material. The ion-selectivity of these materials is such that either anion-exchange or cation-exchange is possible, however one limitation to their use is that more than one sorbent type is required to capture both anions and cations. In this paper, we disclose the design, synthesis and exploitation of a novel SPE sorbent based on microporous polymer microspheres with amphoteric character. We show that it is possible to switch the ion-exchange retention mechanism of the sorbent simply by changing the pH of the loading solution; anion-exchange dominates at low pH, cation-exchange dominates at high pH, and both mechanisms can contribute to retention when the polymer-bound amphoteric species, which are based on the α–amino acid sarcosine (N-methylglycine), are in a zwitterionic state. This is an interesting and useful feature, since it allows distinctly different groups of analytes (acids and bases) to be fractionated using one single amphoteric sorbent with dual-functionality. The sarcosine-based sorbent was applied to the SPE of acidic, basic and amphoteric analytes from ultrapure water, river water and effluent wastewater samples. Under optimised conditions (loading 100 mL of sample at pH 6, washing with 1 mL of MeOH and eluting with an acidic or basic additive in MeOH) the recoveries for most of the compounds were from 57% to 87% for river water and from 61% to 88% for effluent wastewater. We anticipate that these results will lay the basis for the development of a new family of multifunctional sorbents, where two or more separation mechanisms can be embedded within one single, bespoke material optimised for application to challenging chemical separations to give significant selectivity advantages over essentially all other state-of-the-art SPE sorbents

Molecular imprinting : recent developments and the road ahead

Research activity in the area of molecular imprinting has accelerated markedly in recent times. This article gives a brief overview of some recent developments in the field and offers an insight into how the area is likely to evolve in the near future

Non-aqueous dispersion (NAD) polymerisation-based synthetic route to hypercrosslinked polymer : effect of reaction temperature and solvent system on specific surface area

Hypercrosslinked polymer microspheres with high specific surface areas were prepared successfully by exposing reactive, gel-type polymer precursors to a Friedel-Crafts catalyst. The lightly crosslinked gel-type polymer precursors were synthesised by non-aqueous dispersion (NAD) polymerisation in microsphere form, and were used subsequently in hypercrosslinking reactions. Extensive microporosity was generated in the products, leading to remarkably high inner specific surface areas of up to ~1,500 m2/g. SEM and BET spectroscopy were used to monitor the course of the hypercrosslinking reactions

Molecularly imprinted monodisperse microspheres for competitive radioassay

In the present study, molecularly imprinted affinity sorbents against theophylline and 17β-estradiol are synthesised via precipitation polymerisation, a synthetic method that yields monodisperse, spherical polymer particles in the micronscale range, quickly, cleanly and in good yield. The specific binding sites that are created during the imprinting process are analysed via radioligand binding analysis. The molecularly imprinted microspheres are highly specific and have higher load capacities compared to the 'classical' particles obtained by grinding the imprinted monolith. The successful imprinting against model compounds with very different hydrophobicities demonstrates the generality of the current simple approach

Facile synthesis of branched water-soluble poly(dimethylacrylamide)s in conventional and parallel reactors using free radical polymerisation

Water-soluble, branched dimethylacrylamide copolymers have been prepared via facile, one-step, batch solution free-radical polymerisations taken to high conversion. N,N-dimethylacrylamide has been copolymerised with different branching agents (ethylene glycol dimethacrylate, EGDMA and PEG dimethacrylates) using dodecanethiol (DDT) as a chain transfer agent to inhibit gelation. Good yields of soluble branched copolymers have been produced by carrying out individual reactions in conventional glass round-bottomed flasks and also parallel reactions in a Radley's Carousel Reactor. The products have been characterised by size exclusion chromatography and 1H NMR and FT-IR spectroscopies and interestingly though the trends in copolymer structure are similar for products prepared in the conventional glassware and those in the parallel reactor, some systematic differences arise between the two sets of products. This seems to be due in part to the slightly different scale of these reactions, and possibly also to the better sealing of the parallel reactor tubes and hence better exclusion of traces of O2. Branching seems to occur more uniformly with DAM than with the previously studied methyl methacrylate (all other parameters being identical), though the effects of the chain transfer agent, monomer concentration, monomer/chain transfer agent feed ratio and the chain length of the branching agent are similar for both monomers. Also the EGDMA/DDT ratio is at least as important in controlling branching as the absolute amount of EGDMA and DDT incorporated. Highly branched products can therefore be made with relatively low levels of EGDMA and DDT as long as the EGDMA/DDT ratio is high enough, but not so high as to favour cross-linking

Synthesis of uniform polymer microspheres with "living" character using ppm levels of copper catalyst : ARGET atom transfer radical precipitation polymerisation

The first example of activators regenerated by electron transfer atom transfer radical polymerisation (ARGET ATRP) under precipitation polymerisation (PP) conditions is reported. This new method for polymer synthesis (called ARGET ATRPP) requires only very low levels of metal catalyst for success, a distinctive feature that enables the production of uniform polymer microspheres under reversible-deactivation radical polymerisation control. The influence of the polymerisation conditions (monomer concentration, reaction time, initiator and catalyst concentrations) on the polymerisations and microsphere products were investigated and optimised. The ARGET ATRPP methodology was used to prepare polymer microspheres with narrow particle size distributions and mean particle diameters in the micron-size range, under dilute monomer conditions (2%) whilst using very low copper catalyst concentrations (down to 1.7 ppm). The "living" characteristics of the polymer microspheres enabled poly(methyl methacrylate) brushes to be grafted-from the microspheres directly without the need for any additional surface functionalisation step to immobilise initiator moieties