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Methacrylate
Kinds of Methacrylate Terms modified by Methacrylate Selected AbstractsCOVALENT IMMOBILIZATION OF INVERTASE ON CHEMICALLY ACTIVATED POLY (STYRENE-2-HYDROXYETHYL METHACRYLATE) MICROBEADSJOURNAL OF FOOD BIOCHEMISTRY, Issue 3 2008HAYDAR ALTINOK ABSTRACT A carrier for invertase enzyme was synthesized from styrene (S) and 2- hydroxyethyl methacrylate (HEMA) in the form of microbeads. These poly (styrene-2-hydroxyethyl methacrylate), P(S-HEMA) microbeads were activated by epichlorohydrin (ECH) treatment for covalent immobilization. The free and immobilized invertase were assayed in the hydrolysis of sucrose to glucose, and the obtained results were compared. The optimum pH was 4.5 for free and 5.5 for immobilized invertase. The optimum temperature of invertase shifted from 45C to 55C upon immobilization. For free and immobilized enzymes, kinetic parameters were calculated as 4.1 × 10,3 mol L,1and 9.2 × 10,3 mol L,1for Km, and 6.6 × 10,2 mol L,1 min,1and 4.1 × 10,1 mol L,1 min,1for Vmax, respectively. After 1 month of storage at 4C, free enzyme retained 36% of its initial activity, while for the ECH-activated P(S-HEMA) immobilized enzyme, P(S-HEMA)-E, this value was observed as 67%. In repeated batch use, i.e., 20 times in 3 days, 78% retention of the initial activity was observed for P(S-HEMA)-E system. PRACTICAL APPLICATIONS Immobilization of enzymes are very important for many industrial applications, e.g., food, medicine, pharmacology, etc. Invertase converts sucrose to glucose and fructose, which have wide applications in food industry especially as sweeteners. Glucose,fructose mixture has much lower crystallinity compared to sucrose and therefore used in the production of noncrystallizing jams and creams. They are also used as liquid sweeteners. Immobilization enables repeated use, provides significant reduction in the operation costs, facilitates easy separation and speeds up recovery of enzyme and extends the stability of enzyme by protecting the active material from deactivation. Industrial application of immobilized invertase may decrease the production cost of glucose,fructose mixture because it could be used repeatedly for long periods. Although invertase is not a very expensive enzyme, the technique can also be applied to expensive ones for biotechnological productions. [source] Methacrylate-based monolithic column with mixed-mode hydrophilic interaction/strong cation-exchange stationary phase for capillary liquid chromatography and pressure-assisted CECELECTROPHORESIS, Issue 19 2008Jian Lin Abstract A novel porous polymethacrylate-based monolithic column by in situ copolymerization of 3-sulfopropyl methacrylate (SPMA) and pentaerythritol triacrylate in a binary porogenic solvent consisting of cyclohexanol/ethylene glycol was prepared. The monolith possessed in their structures bonded sulfonate groups and hydroxyl groups and was evaluated as a hydrophilic interaction and strong cation-exchange stationary phases in capillary liquid chromatography (cLC) and pressure-assisted CEC using small polar neutral and charged solutes. While the SPMA was introduced as multifunctional monomer, the pentaerythritol triacrylate was used to replace ethylene glycol dimethacrylate as cross-linker with much more hydrophilicity due to a hydroxyl sub-layer. The different characterization of monolithic stationary phases were specially designed and easily prepared by altering the amount of SPMA in the polymerization solution as well as the composition of the porogenic solvent for cLC and pressure-assisted CEC. The resulting monolith showed the different trends about the effect of the permeabilities on efficiency in the pressure-assisted CEC and cLC modes. A typical hydrophilic interaction chromatography mechanism was observed at higher organic solvent content (ACN%>70%) for polar neutral analytes. For polar charged analytes, both hydrophilic interaction and electrostatic interaction contributed to their retention. Therefore, for charged analytes, selectivity can be readily manipulated by changing the composition of the mobile phase (e.g., pH, ionic strength and organic modifier). With the optimized monolithic column, high plate counts reaching greater than 170,000,plates/m for pressure-assisted CEC and 105,000 plates/m for cLC were easily obtained, respectively. [source] Ceramic,Polymer Ba0.6Sr0.4TiO3/Poly(Methyl Methacrylate) Composites with Different Type Composite Structures for Electronic TechnologyINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010Hong Wang Ba0.6Sr0.4TiO3 (BST)/poly(methyl methacrylate) (PMMA) composites with 0,3, 1,3, and 2,2 type structures were prepared and studied. The effect of composite type on the dielectric properties of BST/PMMA composites was comprehensively investigated by both theoretical and experimental methods. The 1,3 type composite shows the highest permittivity and dielectric tunability, while the 2,2 and 0,3 type composites show lower permittivity as well as lower dielectric tunabilities. The experimentally measured dielectric properties are in agreement with the theoretically calculated values. The results help in understanding and tailoring the dielectric properties of ceramic,polymer composites by choosing a suitable composite structure. [source] Synthesis and properties of methacrylate-based networked polymers having ionic liquid structuresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010Kozo Matsumoto Abstract Methacrylate-based networked polymers having ionic liquid structures were prepared by radical copolymerization of methyl methacrylate (MMA) with multifunctional crosslinkers: ethyleneglycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), or triethyleneglycol dimethacrylate (TEGDMA), in the presence of 1-ethyl-3-methylethyl-1-imidazolium bis(trifluoromethane)sulfonyl imide (EMImTFSI). The fundamental physical properties of several film samples prepared by varying the monomer composition and ionic liquid content were investigated. The obtained materials became turbid with increasing crosslinker content and ionic liquid content. Their ionic conductivity increased with increasing ionic liquid content, while it was almost independent of the crosslinker content. EGDMA-derived materials and TMPTMA-derived materials showed higher ionic conductivity than TEGDMA-derived materials. TMPTMA-derived materials showed higher thermal stability than EGDMA or TEGDMA-derived materials. EGDMA and TMPTMA-derived materials were stiffer than the TEGDMA-derived materials. The elastic modulus of the film samples increased but the film became more brittle with the increase of crosslinker content. Scanning electron microscopy and atomic force microscopy observation revealed that phase separation of networked polymers and ionic liquid occurred in the highly crosslinked samples, and the phase separation structures became larger in scale with the increase of crosslinking density. This phase separation was considered to have a strong effect on the mechanical properties of the film samples. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Direct measurements of the addition and recombination of acrylate radicals: Access to propagation and termination rate constants?JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2006J. Lalevée Abstract Acrylate radicals produced by the addition of an aminoalkyl radical to five acrylate monomers were directly observed by transient absorption spectroscopy, which allowed us to easily follow their chemical reactivity. It was possible (1) to characterize their absorption in the visible part of the spectrum, (2) to calculate their absorption properties, (3) to determine the energy barriers of the addition through quantum mechanical calculations, (4) to monitor the kinetics of the subsequent addition to another monomer unit, and (5) to follow the recombination of two acrylate radicals. These two latter points could mimic the propagation and termination reactions of polymerization-propagating acrylate radicals. Methacrylate and acrylonitrile radicals were also studied. The obtained results were in good agreement with the propagation rate constants determined by the well-established pulsed laser polymerization techniques. Our method could likely provide rapid access to both the propagation and termination rate constants in suitable systems and appears to be powerful and promising for studying and comparing the reactivities of different acrylate monomer structures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3577,3587, 2006 [source] Termination Rate Coefficients for Radical Homopolymerization of Methyl Methacrylate and Styrene at Low Conversion,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2010David R. Taylor Abstract A comprehensive and systematic study of overall termination rate coefficients, kt, in low-conversion radical (homo)polymerization of methyl methacrylate and styrene is presented. Values of kt were determined by gravimetric analysis of steady-state experiments, employing 2,2,-azoisobutyronitrile as initiator. The values delivered by this simple method were found to be in qualitative and quantitative agreement with those from more modern and sophisticated techniques for measuring kt. Accordingly, correlations for bulk, low-conversion kt as a function of temperature are given for each monomer. The effects of initiator concentration, cI, and temperature on bulk kt were studied in a controlled way for both monomers. Additionally, ethyl benzene was used as solvent in order to investigate rigorously the effect of monomer concentration, cM, on styrene kt. The trends found by these systematic studies were considered in the light of what is known about the chain-length dependence of termination. Styrene's behavior was always found to be qualitatively in accord with expectation, although the variations of kt with cI and cM were not as strong as should be the case. However its activation energy, 15,kJ,·,mol,1, is shown to be almost perfectly in agreement with theory. Methyl methacrylate, on the other hand, is recalcitrant in that its overall kt does not make manifest the chain-length dependent termination that has been directly measured by other techniques. Possible reasons for these discrepancies are discussed, as are reasons for the difference in values between kt for the two monomers. On the latter topic it is concluded likely that the chain-length dependence of termination at short chain lengths is primarily responsible for styrene having kt that is higher by a factor of about 3, with there also being a contribution that arises from styrene's slower propagation. [source] Free Radical Graft Copolymerization of Methyl Methacrylate onto Polyolefin Backbone: Kinetics Modeling through Model Compounds ApproachMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 13-14 2009Thierry Badel Abstract The grafting of poly(methyl methacrylate) (PMMA) from poly[ethylene- co -(1-octene)] in the molten state by in situ radical polymerization of methyl methacrylate (MMA) was investigated through a kinetic modeling using a model compound approach. We resorted to pentadecane (C15H32) and 2,6,10,15,19,23-hexamethyltetracosane (Squalane, C30H62) as models for both the copolymer ethylene and octene moieties. The attention was focused on the simulation of MMA conversion and PMMA average polymerization degree according to temperature, reaction time, and initiator ratio required for the polymerization of MMA in the presence of alkoxyl radicals and alkanes. [source] Atom Transfer Radical Polymerization of Glycidyl Methacrylate: A Functional MonomerMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2004Pedro Francisco Cañamero Abstract Summary: A detailed investigation of the polymerization of glycidyl methacrylate (GMA), an epoxy-functional monomer, by atom transfer radical polymerization (ATRP) was performed. Homopolymers were prepared at relatively low temperatures using ethyl 2-bromoisobutyrate (EBrIB) as the initiator and copper halide (CuX) with N,N,N,,N,,N,-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The high polymerization rate in the bulk did not permit polymerization control. However, homopolymerization in solution enabled us to explore the effects of different experimental parameters, such as temperature, solvent (toluene vs. diphenyl ether) and initiator concentration, on the controllability of the ATRP process. SEC analysis of the homopolymers synthesized confirmed the importance of solvent character on molecular weight control, the lowest polydispersity indices () and the highest efficiencies being found when the polymerizations were performed in diphenyl ether in combination with a mixed halide technique. A novel poly(glycidyl methacrylate)- block -poly(butyl acrylate) (PGMA- b -PBA) diblock copolymer was prepared through ATRP using PGMA-Cl as a macro-initiator. This chain growth experiment demonstrated a good living character under the conditions employed, while simultaneously indicating a facile synthetic route for this type of functional block copolymer. In addition, the isotacticity parameter for the PGMAs obtained was estimated using 1H NMR analysis which gave a value of ,GMA,=,0.26 in agreement with that estimated in conventional radical polymerization. SEC chromatograms of PGMA-Cl macroinitiator and PGMA- b -PBA diblock copolymer. [source] Effect of LiClO4 and LiCl Additives on the Kinetics of Anionic Polymerization of Methyl Methacrylate in Toluene-Tetrahydrofuran Mixed SolventMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2003Mahua G. Dhara Abstract The kinetics of anionic polymerization of MMA has been studied at ,78,°C in toluene-THF (9:1 v/v) using 1,1,-diphenylhexyl lithium as initiator in the presence of lithium perchlorate and lithium chloride as Lewis acid additives. The control of the polymerization is lost in the absence of additives as evident from the non-linear first-order time-conversion plot and polymers with broad multimodal molecular weight distribution. The presence of LiClO4 and LiCl in 10:1 and 5:1 ratio, respectively, over the initiator brings about sufficient control, yielding polymers of narrow unimodal distribution throughout the polymerization. The reaction in the presence of the additives follows first-order kinetics free of termination and transfer. Moreover, the order with respect to the active centers is found to be almost unity, which signifies a probable disaggregation of ion-pairs to a single complexed propagating species. GPC elugrams at different conversions for MMA polymerization in the presence of LiClO4. [source] Concurrent Initiation by Air in the Atom Transfer Radical Polymerization of Methyl MethacrylateMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2003Ajaya Kumar Nanda Abstract The effect of air in atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was studied. Air initiated polymerization was clearly noticed by the appearance of a low molecular weight peak in the synthesis of high molecular weight poly(isobutylene)- graft -poly(methyl methacrylate) (Mn,=,5.0,×,105 g/mol). The concentration of chains initiated by oxygen (air) was ,8,×,10,4 mol/L, determined using the Gladstone-Dale relationship. The tentatively proposed mechanism for air initiated polymerization was supported by kinetic studies. Similar to typical ATRP systems, the rate of air initiated polymerization increased with temperature, [MMA], amount of air, and activity of the catalyst complex. Polymers with lower polydispersities (Mw/Mn,=,1.13) were obtained in the presence of Cu(II) as compared to Cu(I) catalyst complex system. Kinetic plots for the air initiated bulk polymerization of MMA at (,) 20,°C, (,) 50,°C, and (,) 90,°C. [source] Functionalization of LDPE by Melt Grafting with Glycidyl Methacrylate and Reactive Blending with Polyamide-6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2003Qian Wei Abstract Low-density polyethylene (LDPE) was functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed for reactive blending with polyamide-6 (PA6). The effect of the reaction procedure on the grafting degree of LDPE- g -GMA samples (0.5,12.5 wt.-% GMA) was analyzed as a function of the concentration of GMA monomer, radical initiator (BTP), and addition of styrene as co-monomer. Optimized grafting conditions were obtained when the amount of the monomer is below 10 wt.-% and that of peroxide in the range 0.2,0.4 wt.-%. Binary blends of PA6 with LDPE- g -GMA (3.5 wt.-% GMA) and with LDPE at various compositions (80/20, 67/33, 50/50 wt.-%) were prepared in an internal mixer and their properties were evaluated by torque, SEM and DSC analyses. Morphological examination by SEM showed a large improvement of phase dispersion and interfacial adhesion in PA6/LDPE- g -GMA blends as compared with PA6/LDPE blends. The average diameter of dispersed polyolefin particles was about 0.4 ,m for LDPE- g -GMA contents <,50 wt.-%. A marked increase of melt viscosity was observed for the compatibilized blends depending on the concentration of grafted polyolefin, and it was accounted for by the reaction between the epoxy groups of GMA and the carboxyl/amine end-groups of PA6. The variation of torque was thus related to the molar ratio of reactive group concentration. The analysis of crystallization and melting behavior pointed out marked differences in the phase structure of the blends due to the presence of the functionalized polyolefin. Finally, the in situ formation of a graft copolymer between LDPE- g -GMA and PA6 was investigated by means of a selective dissolution method (Molau test) and by FT-IR and DSC analyses. SEM micrograph of fracture surface of PA6/LDPE- g -GMA 50/50 blend. [source] The Influence of Hydrogen Bonding on the Propagation Rate Coefficient in Free-Radical Polymerizations of Hydroxypropyl MethacrylateMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2003Sabine Beuermann Abstract The propagation rate coefficient kp was determined for hydroxypropyl methacrylate by applying pulsed laser initiated polymerizations and subsequent analysis of the polymer by size-exclusion chromatography. kp data were derived for polymerizations in bulk and in several solvents: toluene, tetrahydrofuran (THF), benzyl alcohol, and supercritical CO2. With the exception of THF, no solvent influence on kp was observed. For polymerizations in THF kp values 40% below the corresponding bulk data were obtained. In addition, the activation energy of kp for polymerizations in THF is higher than for the other systems. The results are explained by a complexation of the OH group contained in the ester group with THF. As a consequence, H bonds between OH groups and carbonyl O atoms, which occur in the other systems, are not formed in the presence of THF. This explanation is supported by Raman spectra, which show that association of carbonyl groups does not occur for systems containing THF, whereas for all other systems the occurrence of two peaks at 1,703 cm,1 and 1 720 cm,1 is indicative of the vibrations of two different , associated vs. not associated , types of carbonyl groups. Based on the change in activation energy it is suggested that a true kinetic solvent effect occurs. Temperature dependence of kp for HPMA polymerizations in bulk and in solution of THF. The literature data for bulk polymerizations are taken from ref. 22. Open symbols refer to ,rep,=,10 Hz and filled symbols to ,rep,=,25 Hz. [source] Morphological and Physical Properties of Triblock Copolymers of Methyl Methacrylate and 2-Ethylhexyl MethacrylateMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2006Hormoz Eslami Abstract Summary: Triblock copolymers of methyl methacrylate (MMA) and 2-ethylhexyl methacrylate (EHMA) [that is, poly(MMA,EHMA,MMA)] were prepared by an emulsion atom-transfer radical polymerization. The relationships of their structural, morphological, and physical properties were investigated. The latex particles had core-shell morphologies and the block copolymers experienced phase separation. Small latex particles with a low number of cores could deform and wet silicon-wafer surfaces, but the deformation of large latex particles was restricted by the internal two-phase morphology of the particles. Latex casting produced continuous pinhole-free films, in which hard poly(MMA) (PMMA) cores of different latex particles merged and provided interparticle connections. The morphology of solution-cast films depended on block composition, solvent type, and film thickness. For all the prepared polymer samples, thick films cast in toluene had poly(EHMA) (PEHMA) materials at air surface, whereas those cast in tetrahydrofuran had a sponge-like PMMA surface structure. Thin toluene-cast films from P(MMA,EHMA,MMA) with the block degrees of polymerization () 200,930,200 showed spherical PMMA domains and those from 380,930,380 yielded a protruded worm-like PMMA structure. The copolymer materials were coated on a glass surface for peeling tests. The films gave good hot-melt adhesion properties when the of the PEHMA block was over 600. The peeling strength depended on the lengths of both PEHMA and PMMA blocks. The P(MMA,EHMA,MMA) sample with of 310,930,310 yielded the highest peeling strength of 7.4 kgf,·,inch,1. The developed material is demonstrated to be a good candidate for a solvent-free, hot-melt, pressure-sensitive adhesives for special-purpose applications such as medical tapes and labels. [source] Waste and Virgin LDPE/PET Blends Compatibilized with an Ethylene-Butyl Acrylate-Glycidyl Methacrylate (EBAGMA) Terpolymer, 1MACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Mustapha Kaci Abstract Summary: This work is aimed at studying the morphology and the mechanical properties of blends of low density polyethylene (LDPE) and poly(ethylene terephthalate) (PET) (10, 20, and 30 wt.-% of PET), obtained as both virgin polymers and urban plastic waste, and the effect of a terpolymer of ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) as a compatibilizer. LDPE and PET are blended in a single screw extruder twice; the first extrusion to homogenize the two components, and the second to improve the compatibilization degree when the EBAGMA terpolymer is applied. Scanning electron microscopy (SEM) analysis shows that the fractured surface of both the virgin polymer and the waste binary blends is characterized by a gross phase segregation morphology that leads to the formation of large PET aggregates (10,50 µm). Furthermore, a sharp decrease in the elongation at break and impact strength is observed, which denotes the brittleness of the binary blends. The addition of the EBAGMA terpolymer to the binary LDPE/PET blends reduces the size of the PET inclusions to 1,5 µm with a finer dispersion, as a result of an improvement of the interfacial adhesion strength between LDPE and PET. Consequently, increases of the tensile properties and impact strength are observed. SEM micrographs of the fracture surface of a waste 70/30 LDPE/PET blend (R30) and of its blend with 15 pph of EBAGMA (R30C). Magnification,×,1,000. [source] Microwave-Assisted Free Radical Copolymerizations of Styrene and Methyl MethacrylateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2007Heiner Stange Abstract Free radical copolymerizations of styrene and MMA were performed in toluene and DMF as solvents using different peroxide initiators with and without microwave irradiation. A general trend showed significant solvent dependence of monomer conversion rate only for copolymerizations initiated by tert -butyl perbenzoate in DMF compared to toluene but nearly no impact for copolymerizations initiated by dicumyl peroxide and dibenzoyl peroxide. Significant variations in copolymer composition were not observed for reactions under conventional heating compared to microwave irradiation. It was concluded that enhanced initiator decomposition under microwave irradiation in DMF accelerate polymerization of styrene and MMA by formation of larger amount of initiator radicals. [source] Effects of Ionic Liquid [Me3NC2H4OH]+[ZnCl3], on , -Radiation Polymerization of Methyl Methacrylate in Ethanol and N,N -DimethylformamideMACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2005Guozhong Wu Abstract Summary: Radiation-induced polymerization of methyl methacrylate (MMA) in ethanol (EtOH) and N,N -dimethylformamide (DMF) in the presence of ionic liquid [Me3NC2H4OH]+[ZnCl3], is reported. A substantial increase in monomer conversion and molecular weight is observed at room-temperature ionic liquid (RTIL) >60 vol.-%, and the resulting PMMA has a broad multimodal MWD. A clear difference in the MWD pattern is noted between EtOH/RTIL and DMF/RTIL systems, probably due to the complicated interactions between the solvent and ionic liquid. Gel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100. [source] Chain Transfer and Efficiency of End-Group Introduction in Free Radical Polymerization of Methyl Methacrylate in the Presence of Poly(methyl methacrylate) MacromonomerMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Kazuki Miyake Abstract Summary: Experimental and modeling studies of addition,fragmentation chain transfer (AFCT) during radical polymerization of methyl methacrylate in the presence of poly(methyl methacrylate) macromonomer with 2-carbomethoxy-2-propenyl , -ends (PMMA-CO2Me) at 60,°C are reported. The results revealed that AFCT involving PMMA-CO2Me formed in situ during methyl methacrylate polymerization has a negligible effect on the molecular weight distribution. [source] Kinetic Study of the Thermopolymerization of Furfuryl Methacrylate in Bulk by Mathematical Modeling.MACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2009Part A: Simulation of Experimental Data, Sensitivity Analysis of Kinetic Parameters Abstract Mathematical modeling of the thermopolymerization of FM and CMFMA was carried out using a cross-linked kinetic model proposed for the photo-initiated polymerization of acryl-furanic compounds. In this model, the photochemical initiation step was substituted by a thermal one and it was assumed that the constant of radical termination was time-dependent, which allowed the gel effect (Trommsdorff) at high monomer conversion to be simulated. Optimization of all kinetic constants was achieved and the results of simulation suitably fitted the experimental data of the monomer conversion. The contribution of each step in the mechanism and its dependence on the experimental conditions were estimated by a sensitivity analysis technique. [source] Sol MWD During Styrene, Vinyl Acetate, Methyl Methacrylate, and Butyl Acrylate Homopolymerization: A Numerical Study Using the NFT ApproachMACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2009Bibiana Alejandra Yáñez-Martínez Abstract Complete parameter sensitivity analyses using the numerical fractionation technique are presented for the cases of homopolymerization with chain transfer to polymer and termination by combination. Also, using reported values for the kinetic rate constants associated with the linear and non-linear homopolymerizations of styrene, vinyl acetate, methyl methacrylate and butyl acrylate, overall molecular weight distributions and averages of the MWD were calculated using the NFT. Good agreement with the expected behavior, with MMA and STY not gelling while BA and VAc do, was obtained. It is concluded that the NFT produces coherent and reliable performance for known polymerization systems, whether linear or non-linear. [source] Initiated CVD of Poly(2-Hydroxyethyl Methacrylate) Hydrogels: Synthesis, Characterization and In-vitro BiocompatibilityCHEMICAL VAPOR DEPOSITION, Issue 4-6 2009Ranjita K. Bose Abstract Initiated (i)CVD, an all-dry, one-step surface polymerization technique, was used to synthesize thin film hydrogels of poly (2-hydroxyethyl methacrylate) (PHEMA). Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies showed stoichiometric PHEMA films obtained by iCVD. Differential scanning calorimetry (DSC) revealed a high glass transition temperature, indicative of high molecular mass polymer. In-vitro cell studies using adult human dermal fibroblasts (HDF) demonstrated the nontoxic nature and good cell adhesion properties of iCVD PHEMA films. [source] Contact allergy to epoxy (meth)acrylatesCONTACT DERMATITIS, Issue 1 2009Kristiina Aalto-Korte Background: Contact allergy to epoxy (meth)acrylates, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (bis-GMA), 2,2-bis[4-(2-hydroxy-3-acryloxypropoxy)phenyl]-propane (bis-GA), 2,2-bis[4-(methacryl-oxyethoxy)phenyl] propane (bis-EMA), 2,2-bis[4-(methacryloxy)phenyl]-propane (bis-MA), and glycidyl methacrylate (GMA) is often manifested together with contact allergy to diglycidyl ether of bisphenol A (DGEBA) epoxy resin. Objective: To analyse patterns of concomitant allergic reactions to the five epoxy (meth)acrylates in relation to exposure. Methods: We reviewed the 1994,2008 patch test files at the Finnish Institute of Occupational Health (FIOH) for reactions to the five epoxy (meth)acrylates, and examined the patients' medical records for exposure. Results: Twenty-four patients had an allergic reaction to at least one of the studied epoxy (meth)acrylates, but specific exposure was found only in five patients: two bis-GMA allergies from dental products, two bis-GA allergies from UV-curable printing inks, and one bis-GA allergy from an anaerobic glue. Only 25% of the patients were negative to DGEBA epoxy resin. Conclusions: The great majority of allergic patch test reactions to bis-GMA, bis-GA, GMA and bis-EMA were not associated with specific exposure, and cross-allergy to DGEBA epoxy resin remained a probable explanation. However, independent reactions to bis-GA indicated specific exposure. Anaerobic sealants may induce sensitization not only to aliphatic (meth)acrylates but also to aromatic bis-GA. [source] Chemical burn caused by glycidyl methacrylateCONTACT DERMATITIS, Issue 5 2008Ayako Shimizu No abstract is available for this article. [source] Allergic reaction to hydroxyethyl- methacrylate following intradermal filler injectionCONTACT DERMATITIS, Issue 6 2005J. P. Thyssen No abstract is available for this article. [source] Electrochemically Induced Formation of Surface-Attached Temperature-Responsive Hydrogels.ELECTROANALYSIS, Issue 9 2010Amperometric Glucose Sensors with Tunable Sensor Characteristics Abstract Employing thermally responsive hydrogels, the design of an amperometric glucose sensor is proposed. The properties of the biosensor can be modulated upon changing the temperature. Homo- and copolymers of N -isopropylacrylamide (NIPAm) and oligo(ethylene glycol) methacrylate (OEGMA) were prepared by electrochemically induced polymerization thus yielding surface-attached hydrogels. The growth of the films as well as the change in the film thickness in dependence from the temperature were investigated by means of an electrochemical quartz crystal microbalance (EQCM). The layer thickness in the dry state ranged from 20 to 120,nm. The lower critical solution temperature (LCST) of the hydrogel increases with increasing content of the more hydrophilic OEGMA. Hence, the swelling in aqueous electrolyte is composition dependent and can be adjusted by selecting a specific NIPAm to OEGMA ratio. All homo- and copolymer films showed good biocompatibility and no fouling could be observed during exposing the surfaces to human serum albumin. For amperometric glucose detection, glucose oxidase was entrapped in the films during electrochemically-induced polymerization. Both the apparent Michaelis constant (K and the apparent maximum current (i as determined by amperometry could be adjusted both by the film composition as well as the operation temperature. [source] Flow-Through Assay of Quinine Using Solid Contact Potentiometric Sensors Based on Molecularly Imprinted PolymersELECTROANALYSIS, Issue 24 2009Ayman Abstract Miniaturized potentiometric membrane sensors for quinine incorporated with molecular imprinted polymer (MIP) were synthesized and implemented. Planar PVC based polymeric membrane sensors containing quinine-methacrylic and/or acrylic acid-ethylene glycol methacrylate were dispensed into anisotropically etched wells on polyimide wafers. The determination of quinine was carried out in acidic solution at pH,6, where positively charged species predominated prevalently. The suggested miniaturized planner sensors exhibited marked selectivity, sensitivity, long-term stability and reproducibility. At their optimum conditions, the sensors displayed wide concentration ranges of 4.0×10,6,1.0×10,2mol L,1 and 1.0×10,5,1.0×10,2 mol L,1 with slopes of about 61.3,55.7,mV decade,1; respectively. Sensors exhibit detection limits of 1.2×10,6 and 8.2×10,6 mol L,1 upon the use of methacrylic and acrylic acid monomers in the imprinted polymer, respectively. Validation of the assay method according to the quality assurance standards (range, within-day repeatability, between-day variability, standard deviation, accuracy, and good performance characteristics) which could assure good reliable novel sensors for quinine estimation was justified. Application of the proposed flow-through assay method for routine determination of quinine in soft drinks was assayed and the results compared favorably with data obtained by the standard fluorimetric method. [source] Electroconductive Hydrogels: Electrical and Electrochemical Properties of Polypyrrole-Poly(HEMA) CompositesELECTROANALYSIS, Issue 7 2005Sean Brahim Abstract Composites of inherently conductive polypyrrole (PPy) within highly hydrophilic poly(2-hydroxyethyl methacrylate)-based hydrogels (p(HEMA)) have been fabricated and their electrochemical properties investigated. The electrochemical characteristics observed by cyclic voltammetry suggest less facile reduction of PPy within the composite hydrogel compared to electropolymerized PPy, as shown by the shift in the reduction peak potential from ,472,mV for electropolymerized polypyrrole to ,636,mV for the electroconductive composite gel. The network impedance magnitude for the electroconductive hydrogel remains quite low, ca. 100,,, even upon approach to DC, over all frequencies and at all offset potentials suggesting retained electronic (bipolaronic) conductivity within the composite. In contrast, sustained application of +0.7 V (vs. Ag/AgCl, 3,M Cl,) for typically 100,min. (conditioning) to reduce the background amperometric current to <1.0,,A, resulted in complete loss of electroactivity. Nyquist plots suggest that sustained application of such a modest potential to the composite hydrogel results in impedance characteristics that resembles p(HEMA) without evidence of the conducting polymer component. PPy composite gels supported a larger ferrocene monocarboxylate diffusivity (Dappt=7.97×10,5,cm2,s,1) compared to electropolymerized PPy (Dappt=5.56×10,5,cm2,s,1), however a marked reduction in diffusivity (Dappt=1.01×10,5,cm2,s,1) was observed with the conditioned hydrogel composite. Cyclic voltammograms in buffer containing H2O2 showed an absence of redox peaks for electrodes coated with PPy-containing membranes, suggesting possible chemical oxidation of polypyrrole by the oxidant [source] Using the Aggregation of Latex Polymers in the Fabrication of Reproducible Enzyme ElectrodesELECTROANALYSIS, Issue 17 2003Wibowo Rahmat Abstract An enzyme electrode for glucose is described as a model system to demonstrate a fabrication method using latex aggregation and entrapment of enzyme. Electrosterically-stabilized latex particles synthesized by emulsion polymerization in batch from acrylic acid, methyl methacrylate and butyl acrylate, and glucose oxidase were coagulated together at pH,5.5 with ethanol. A platinum disk electrode dipped in the solution becomes coated with latex/enzyme. The relative thickness of the film and relative amount of enzyme may be controlled by the time the electrode is in contact with the solution. The enzyme was then immobilized by covalent attachment of amine groups to carboxylic moieties in the polymer using 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride and N -hydroxysuccinimide. Five minutes contact with the latex/enzyme solution and subsequent amide coupling, gave electrodes with a reproducibility of 5.7% RSD, a wide dynamic range (0,100,mM) and good storage properties. [source] Assay of vitamin B in urine by capillary electrochromatography with methacrylate-based monolithic columnELECTROPHORESIS, Issue 19 2010Xiaoyi Wei Abstract A novel and simple method for the separation of major vitamin B analytes, such as thiamine, riboflavin, nicotinamide, vitamin B4, pyridoxine, has been developed by CEC using the monolithic column. It has been found that the baseline separation of the five analytes could be achieved with 5.0,mM phosphate buffer at pH 4.0. Compared with the open-tubular capillary and the bared capillary columns, the poly(butylmethacrylate-co-ethylene glycol dimethacrylate) monolithic capillary could exhibit the best resolution in the analysis. Then the method was validated and the linear calibration ranges were obtained with correlation coefficients more than 0.997. The precision and the recovery were also investigated and showed a good result. Furthermore, the proposed method was successfully applied to assay the concentration of vitamin B analytes and the metabolic situation in human urine samples. [source] Preparation and characterization of a molecularly imprinted monolithic column for pressure-assisted CEC separation of nitroimidazole drugsELECTROPHORESIS, Issue 16 2010Sulan Liao Abstract A polymethacrylate-based molecularly imprinted monolithic column bearing mixed functional monomers, using non-covalent imprinting approach, was designed for the rapid separation of nitroimidazole compounds. The new monolithic column has been prepared via simple in situ polymerization of 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and ethylene dimethacrylate, using (S)-ornidazole ((S)-ONZ) as template in a binary porogenic mixture consisting of toluene and dodecanol. The composition of the polymerization mixture was systematically altered and optimized by altering the amount of monomers as well as the composition of the porogenic solvent. The column performance was evaluated in pressure-assisted CEC mode. Separation conditions such as pH, voltage, amount of organic modifier and salt concentration were studied. The optimized monolithic column resulted in excellent separation of a group of structurally related nitroimidazole drugs within 10,min in isocratic elution condition. Column efficiencies of 99,000, 80,000, 103,000, 60,000 and 99,000,plates/m were obtained for metronidazole, secnidazole, ronidazole, tinidazole and dimetridazole, respectively. Parallel experiments were carried out using molecularly imprinted and non-imprinted capillary columns. The separation might be the result of combined effects including hydrophobic, hydrogen bonding and the imprinting cavities on the (S)-ONZ-imprinted monolithic column. [source] Parameters governing reproducibility of flow properties of porous monoliths photopatterned within microfluidic channelsELECTROPHORESIS, Issue 14 2010Mei He Abstract We report the patternability as well as the reproducibility and stability of flow resistance of polymer monolithic beds photopatterned within microfluidic channels as a function of initial reagent composition and preparation conditions. 2-Hydroxyethyl methacrylate and ethylene dimethacrylate-based polymer monoliths were selectively photopatterned within microchannels and their flow resistance was evaluated using a photobleaching, TOF linear flow rate measurement method developed in our lab. This measurement technique was found to be significantly more informative for columns formed in microfluidic channels compared with bulk monolith characterization by mercury intrusion porosimetry. 1-Octanol was determined to provide sharp bed edge formation and relatively low flow resistance by photopatterning relative to other porogenic solvents. Compared with literature formulations which did not achieve good flow stability and reproducibility from batch to batch, using 2-hydroxyethyl methacrylate, ethylene dimethacrylate and 1-octanol as porogenic solvents, less than 4% RSD was achieved in flow stability over 7 days for monoliths prepared with 60,80% crosslinker(monomer+crosslinker) ratio. Column-to-column variation of 5% RSD was obtained in this composition range. These results demonstrate that photopatterning of uniform polymer monolithic beds, which is critical for applications in multiplexed microfluidic systems, requires careful attention to the parameters that affect reproducibility, specifically the porogenic solvent choice and the crosslinker to monomer ratio. [source] | |||||||||||||||||||||||||||||||||||||