Conventional free radical polymerization in room temperature ionic liquids: a green approach to commodity polymers with practical advantages

Free-radical polymerization of methyl methacrylate and styrene using conventional organic initiators in the room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([ C(4)mim][PF6]) is rapid and produces polymers with molecular weights up to 10x higher than from benzene; both polymerization and isolation of products were achieved without using VOCs, offering economic as well as environmental advantages.

Remediation of phenol-contaminated water by adsorption using poly(methyl methacrylate) (PMMA)

Recently polymeric adsorbents have been emerging as highly effective alternatives to activated carbons for pollutant removal from industrial effluents. Poly(methyl methacrylate) (PMMA), polymerized using the atom transfer radical polymerization (ATRP) technique has been investigated for its feasibility to remove phenol from aqueous solution. Adsorption equilibrium and kinetic investigations were undertaken to evaluate the effect of contact time, initial concentration (10-90 mg/L), and temperature (25-55 degrees C). Phenol uptake was found to increase with increase in initial concentration and agitation time. The adsorption kinetics were found to follow the pseudo-second-order kinetic model. The intra-particle diffusion analysis indicated that film diffusion may be the rate controlling step in the removal process. Experimental equilibrium data were fitted to five different isotherm models namely Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Redlich-Peterson by non-linear least square regression and their goodness-of-fit evaluated in terms of mean relative error (MRE) and standard error of estimate (SEE). The adsorption equilibrium data were best represented by Freundlich and Redlich-Peterson isotherms. Thermodynamic parameters such as Delta G degrees and Delta H degrees indicated that the sorption process is exothermic and spontaneous in nature and that higher ambient temperature results in more favourable adsorption. (C) 2011 Elsevier B.V. All rights reserved.

Nanoscale detection of metal-labeled copolymers in patchy polymersomes

We report the synthesis of polymersome-forming block copolymers using two different synthetic routes based on Atom Transfer Radical Polymerization (ATRP) and Reversible Addition Fragmentation chain Transfer (RAFT) polymerization, respectively. Functionalization with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) allowed the block copolymer chains to be labelled with electron-dense metal ions (e.g. indium). The resulting metal-conjugated copolymers can be visualized by transmission electron microscopy with single chain resolution, hence enabling the study of polymer/polymer immiscibility and phase separation on the nano-scale.

Characterization of the physicochemical, antimicrobial, and drug release properties of thermoresponsive hydrogel copolymers designed for medical device applications

In this study, a series of hydrogels was synthesized by free radical polymerization, namely poly(2-(hydroxyethyl) methacrylate) (pHEMA), poly(4-(hydroxybutyl)methacrylate) (pHBMA), poly(6-(hydroxyhexyl)methacrylate) (pHHMA), and copolymers composed of N-isopropylacrylamide (NIPAA), methacrylic acid (MA), NIPAA, and the above monomers. The surface, mechanical, and swelling properties (at 20 and 37 degrees C, pH 6) of the polymers were determined using dynamic contact angle analysis, tensile analysis, and thermogravimetry, respectively. The T-g and lower critical solution temperatures (LCST) were determined using modulated DSC and oscillatory rheometry, respectively. Drug loading of the hydrogels with chlorhexidine diacetate was performed by immersion in a drug solution at 20 degrees C (

Application of ionic liquids as plasticizers for poly(methyl methacrylate)

The room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, [C(4)mim][PF6] was found to be an efficient plasticizer for poly( methyl methacrylate), prepared by in situ radical polymerization in the ionic liquid medium; the polymers have physical characteristics comparable with those containing traditional plasticizers and retain greater thermal stability.

Facile synthesis of thiol-functionalized amphiphilic polylactide–methacrylic diblock copolymers

Biodegradable amphiphilic diblock copolymers based on an aliphatic ester block and various hydrophilic methacrylic monomers were synthesized using a novel hydroxyl-functionalized trithiocarbonate-based chain transfer agent. One protocol involved the one-pot simultaneous ring-opening polymerization (ROP) of the biodegradable monomer (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione (L-lactide, LA) and reversible addition–fragmentation chain transfer (RAFT) polymerization of 2-(dimethylamino)ethyl methacrylate (DMA) or oligo(ethylene glycol) methacrylate (OEGMA) monomer, with 4-dimethylaminopyridine being used as the ROP catalyst and 2,2′-azobis(isobutyronitrile) as the initiator for the RAFT polymerization. Alternatively, a two-step protocol involving the initial polymerization of LA followed by the polymerization of DMA, glycerol monomethacrylate or 2-(methacryloyloxy)ethyl phosphorylcholine using 4,4′-azobis(4-cyanovaleric acid) as a RAFT initiator was also explored. Using a solvent switch processing step, these amphiphilic diblock copolymers self-assemble in dilute aqueous solution. Their self-assembly provides various copolymer morphologies depending on the block compositions, as judged by transmission electron microscopy and dynamic light scattering. Two novel disulfide-functionalized PLA-branched block copolymers were also synthesized using simultaneous ROP of LA and RAFT copolymerization of OEGMA or DMA with a disulfide-based dimethacrylate. The disulfide bonds were reductively cleaved using tributyl phosphine to generate reactive thiol groups. Thiol–ene chemistry was utilized for further derivatization with thiol-based biologically important molecules and heavy metals for tissue engineering or bioimaging applications, respectively.

Hydrogel antimicrobial capture coatings for endotracheal tubes; a pharmaceutical strategy designed to prevent ventilator-associated pneumonia.

This paper presents a novel strategy for the prevention of ventilator-associatedpneumonia that involves coating poly(vinyl chloride, PVC) endotracheal tubes (ET) withhydrogels that may be subsequently used to entrap nebulized antimicrobial solutions. Candidatehydrogels were prepared containing a range of ratios of hydroxyethyl methacrylate (HEMA) andmethacrylic acid (MAA) from 100:0 to 70:30 using free radical polymerization and, whenrequired, simultaneous attachment to PVC was performed. The mechanical properties, glasstransition temperatures, swelling kinetics, uptake of gentamicin from an aqueous medium, andgentamicin release were characterized. Increasing the MAA content of the hydrogels significantlydecreased the ultimate tensile strength, % elongation at break, Young’s modulus, and increasedthe glass transition temperature, the swelling ratio, and gentamicin uptake. Microbial(Staphylococcus aureus and Pseudomonas aeruginosa) adherence to control (drug-free) hydrogelswas observed; however, while adherence to gentamicin-containing p(HEMA) occurred, noadherence occurred to gentamicin-containing HEMA:MAA copolymers. Antimicrobialpersistence of gentamicin-containing hydrogels was examined by determining the zone ofinhibition against each microorganism on successive days. Hydrogel composition affected the observed antimicrobial persistence,with the hydrogel composed of 70:30 HEMA:MAA exhibiting >20 days persistence against S. aureus and P. aeruginosa,respectively. To simulate clinical use, the hydrogels (coated onto PVC) were first exposed to a nebulized solution of gentamicin(4 mL, 80 mg for 20 min), and then to nebulized bacteria (4 mL ca. 1 × 109 colony forming units mL−1, 30 min). Viable bacteriawere not observed on the gentamicin-treated p(HEMA: MAA) copolymers, whereas growth was observed on gentamicin-treatedp(HEMA). In light of the excellent antimicrobial activity and physicochemical properties, p(HEMA: MAA) copolymerscomposed of ratios of 80:20 or 70:30 HEMA: MAA were identified as potentially useful coatings of endotracheal tubes to be usedin conjunction with the clinical nebulization of gentamicin and designed for the prevention of ventilator-associated pneumonia

Radical 1,4-aryl transfer in arylcarboxamides leading to phthalimides, biaryls and enantiomerically enriched beta-arylethylamines

5-exo Cyclisation of vinyl-, aryl- and alkyl-radicals onto the aryl group of arylcarboxamides is followed by beta-scission of the resulting spirocyclohexadienyl radicals with ejection of a carbamoyl radical. The fate of this radical depends on the substrate but, in the cases studied, either 5-endo cyclisation or direct reduction follows to give phthalimides, biaryls or beta-arylethylamines.

Three different types of quasi-model networks: synthesis by group transfer polymerization and characterization

Group transfer polymerization (GTP) chemistry was employed for the preparation of polymethacrylate networks of controlled structure (quasi-model networks) of three different types: (a) regular quasi-model networks, in which all polymer chains were linked at their ends, leaving, in principle, no free chain ends, (b) crosslinked star polymer quasi-model networks, in which star polymers were interlinked via half of their chains, letting the other half free (dangling), and (c) shell-crosslinked polymer quasi-model networks, in which the outer part of the network contained polymer arms (dangling chains). Combination of hydrophilic and hydrophobic monomers led to amphiphilic networks whose aqueous swelling behavior was characterized gravimetrically.

Behavior of the heterogeneous electron-transfer rate constants of arenes and substituted anthracenes in room-temperature ionic liquids

We report the anodic oxidation of several arenes and anthracenes within room-temperature ionic liquids (RTILs). In particular, the heterogeneous electron-transfer rates (k(0)) for substituted anthracenes and arenes are also investigated in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(2)mim][NTf2]) and found not to obey the outer-sphere Marcus-type behavior of these compounds in contrast to the behavior in traditional organic solvents,in particular the predictions for k(0) with molecular size and solvent static dielectric constant. To obtain the electron-transfer rate for 9-phenylanthracene, the dimerization and heterogeneous electron-transfer kinetics of its electrogenerated radical cations is studied in [C(2)mim][NTf2] and eight other RTILs and are both found to be largely independent of the solution viscosity.

Changed reactivity of the 1-bromo-4-nitrobenzene radical anion in a room temperature ionic liquid

Radical anions of 1-bromo-4-nitrobenzene (p-BrC6H4NO2) are shown to be reactive in the room temperature ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ([C(4)mPyrr][NTf2]), by means of voltammetric measurements. In particular, they are shown to react via a DISP type mechanism such that the electrolysis of p-BrC6H4NO2 occurs consuming between one and two electrons per reactant molecule, leading to the formation of the nitrobenzene radical anion and bromide ions. This behaviour is a stark contrast to that in conventional non-aqueous solvents such as acetonitrile, dimethyl sulfoxide or N,N-dimethylformamide, which suggests that the ionic solvent promotes the reactivity of the radical anion, probably via stabilisation of the charged products.

Transfer of amiprophosmethyl resistance from a Nicotiana plumbaginifolia mutant by somatic hybridisation

Transfer of resistance to the phosphorothioamidate herbicide, amiprophosmethyl (APM), from the P-tubulin mutant of Nicotiana plumbaginifolia to the interspecific N, plumbaginifolia (+) N, sylvestris is and to the intertribal N, plumbaginifolia (+) Atropa belladonna somatic hybrids has been demonstrated. Transfer to the recipient species was accomplished by: (1) symmetric hybridisation and (2) asymmetric hybridisation using gamma-irradiation of donor protoplasts. Cytogenetic analysis confirmed the hybrid origin of the hybrids obtained. It was established that most of them typically inherited no more than three donor chromosomes, although it was possible to obtain symmetric hybrids in the case of symmetric fusion. Immunofluorescent microscopy analysis has shown that protoplasts of the mutant, and of the N. plumbagini-folia (+) N. sylvestris and N. plumbaginifolia (+) A. belladonna hybrids, retained the normal structure of interphase microtubule (MT) arrays and mitotic figures after treatment with 5 mu M APM, whereas MTs of protoplasts of the recipients were destroyed under these conditions. It was also shown that hybrid clones contained an altered beta-tubulin isoform originating from the N. plumbaginifolia mutant. The selected hybrid clones were characterised by cross-resistance to trifluralin, a dinitroaniline herbicide with the same mode of anti-MT action. Some of the somatic hybrids which could flower were fertile. It was established that seeds of some fertile hybrids were able to germinate in the presence of 5 mu M APM. The results obtained thus support the conclusion that the technique of somatic hybridisation, especially asymmetric fusion, can be used to transfer APM resistance from the N. plumbaginifolia mutant to different (related and remote) plant species of the Solanaceae, including important crops.

Photoelectrochemistry with quinone radical anions: Kinetics of homogeneous redox catalysis

Cyclic voltammograms of quinones were recorded in acetonitrile in the presence of various substrates: carbonyl compounds, halobenzenes, Methyl Viologen and Neutral Red. When illuminated with light of λ >410 nm, catalytic waves were observed. From the ratio of the catalysed to uncatalysed peak current, electron transfer rate constants were calculated using the working curves of Saveant and coworkers. The values of these rate constants were compared with the values obtained by Shukla and Rusling for different systems using a similar method and with quenching rate constants calculated using Rehm-Weller-Marcus theory.