Tri Methyl Research Articles

The effect of structure on the thermoresponsive nature of well‐defined poly(oligo(ethylene oxide) methacrylates) synthesized by ATRP

AbstractStatistical copolymers of di(ethylene glycol) methyl ether methacrylate (MEO2MA) and tri(ethylene glycol) methyl ether methacrylate (MEO3MA) were synthesized by atom transfer radical polymerization (ATRP) providing copolymers with controlled composition and molecular weights ranging from Mn = 8,300–56,500 with polydispersity indexes (Mw/Mn) between 1.19 and 1.28. The lower critical solution temperature (LCST) of the copolymers increased with the mole fraction of MEO3MA in the copolymer over the range from 26 to 52 °C. The average hydrodynamic diameter, measured by dynamic light scattering, varied with temperature above the LCST. These two monomers were also block copolymerized by ATRP to form polymers with molecular weight of Mn = 30,000 and Mw/Mn from 1.12 to 1.21. The LCST of the block copolymers shifted toward the LCST of the major segment, as compared to the value measured for the statistical copolymers at the same composition. As temperature increased, micelles, consisting of aggregated PMEO2MA cores and PMEO3MA shell, were formed. The micelles aggregated upon further heating to precipitate as larger particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 194–202, 2008

Detection of bicontinuous phase in some reverse micellar systems by positron lifetime spectroscopy

AbstractPositron lifetime measurements have been made in some reverse micellar systems of cetyl tri methyl ammonium bromide (CTAB)/hexanol and tetra‐decyl‐tri‐methyl‐ ammonium‐bromide (TTAB)/pentanol by adding increasing amount of water in each system. For both the systems, the dependence of positron lifetime parameters on water concentration indicates the existence of bicontinuous phase in so called single reverse micellar phase. The results of this investigation have been presented in this paper. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The Minimal Structural Requirement of Concanavalin A that Retains Its Functional Aspects

A systematic investigation of the effects of several commonly used detergents on the conformation and function of concanavalin A at pH 7 in solution form was made by using circular dichroism (CD), intrinsic fluorescence, 1-anilino 8-sulphonic acid (ANS) binding, dynamic light scattering (DLS) and sugar inhibition assay. In the presence of 6.0 mM sodium dodecyl sulphate (SDS), an anionic detergent, and 0.8 mM cetyl tri methyl ammonium bromide (CTAB), a cationic detergent, intermediate states of concanavalin A were obtained having a negative CD peaks at 222 and 208 nm respectively, a characteristic of alpha-helix. These states also retained tertiary contacts with altered tryptophan environment and high ANS binding (exposed hydrophobic area) which can be characterized as molten globule states. Concanavalin A in the presence of 5.0 mM 3-[(3-cholamidopropyl) dimethyl-ammonio]-1-propanesulphonate (CHAPS), a zwitterionic detergent, and 0.07 mM brij-35, a non-ionic detergent, also exists in intermediate states. These intermediates (molten globules) had high ANS binding with native-like secondary (inherent beta-sheet) and tertiary structure. The intermediate states were characterized further by means of dynamic light-scattering measurements and kinetic data. To study the possible functional requirement of the minimum structure, the intermediate states characterized in the presence of detergents were shown to retain the activity with polysaccharide (dextran). The pattern of activity observed was brij-35 > CHAPS > CTAB > SDS. The specific binding and activity of concanavalin A with ovalbumin was investigated as a function of time by turbidity measurements. Cationic and anionic detergents showed significant effects on the structure of concanavalin A as compared with zwitterionic and non-ionic detergents.

The reaction of thioanisole with tetraperoxomolybdate ion in comicelles of Aliquat-336 and cetyl trimethylammonium mesylate

Addition of sparingly soluble Aliquat-336 (methyl tri- n-octylammonium chloride) to cetyl trimethylammonium mesylate (CTAOMs) in two-fold molar excess generates comicelles, as shown by changes in 1H and 35Cl NMR spectra, and conformational changes in Aliquat allow it to enter the comicelles. These comicelles behave similarly to micelles and comicelles of cetylpyridinium chloride (CPyCl) as reaction media for the oxidation of thioanisole (PhSMe) mediated by tetraperoxomolybdate ion (Mo(O 2) 4 2−). Second-order rate constants in terms of local concentrations in the micellar interfacial regions are consistently lower than second-order rate constants in H 2O- t-BuOH (7:3, v/v) and are slightly lower in micelles and comicelles of CTAOMs than in those of CPyCl. In some conditions sodium “percarbonate” (Na 2CO 3, 1.5 H 2O 2) can replace hydrogen peroxide (H 2O 2), although this system was not examined quantitatively.

Seasonal environmental changes regulate the expression of the histone variant macroH2A in an eurythermal fish

Adaptation to cold and warm conditions requires dramatic change in gene expression. The acclimatization process of the common carp Cyprinus carpio L. in its natural habitat has been used to study how organisms respond to natural environmental changes. At the cellular level, adaptation to cold condition is accompanied by a dramatic alteration in nucleolar structure and a down regulation of the expression of ribosomal genes. We show that the enrichment of condensed chromatin in winter adapted cells is not correlated with an increase of the heterochromatin marker trimethyl and monomethyl K20H4. However, the expression of the tri methyl K4 H3 and of the variant histone macroH2A is significantly increased during the winter season together with a hypermethylation of CpG residues. Taking into account the properties of macroH2A toward chromatin structure and dynamics and its role in gene repression our data suggest that the increased expression of macroH2A and the hypermethylation of DNA which occurs upon winter-acclimatization plays a major role for the reorganization of chromatin structure and the regulation of gene expression during the physiological adaptation to a colder environment.

Adhesion study of tetra methyl cyclo tetra siloxanes (TMCTS) and tri methyl silane (3MS)-based low- k films

Chemical vapor deposited (CVD) low- k films using tri methyl silane (3MS) precursors and tetra methyl cyclo tetra siloxanes (TMCTS) precursors were studied. Films were deposited by means of four processes, namely, O 2, O 2 + He process and CO 2, CO 2 + O 2 process for 3MS and TMCTS precursors, respectively. Interfacial adhesion energy ( G c), of low- k/Si samples, as measured by a 4-point bending test displayed a linear relationship with film hardness and modulus. Fractography studies indicated two possible failure modes with the primary interface of delamination being either at low- k/Si or Si/epoxy interface. In the former, once delamination initiated at the low- k/Si interface, secondary delamination at the Si/epoxy and epoxy/low- k interfaces was also observed. Films with low hardness (<5 GPa) displayed a low G c (<10 J/m 2) with an adhesive separation of Si/epoxy, epoxy/low- k, and low- k/Si interfaces. Whereas, films of high hardness (>5 GPa) displayed interfacial energies in excess of 10 J/m 2 with separation of Si/epoxy and epoxy/low- k interfaces, thus indicating excellent adhesion between the Si and low- k films. Films with high hardness have less carbon in the system causing it to be more “silicon dioxide” like and exhibiting better adhesion with the Si substrate.

Water-Soluble Cationic Poly(p-phenyleneethynylene)s (PPEs): Effects of Acidity and Ionic Strength on Optical Behavior

Three cationic PPEs P1‘−P3‘ were obtained through quaternization of their neutral polymers, of which all side chains were respectively featured with a tertiary amino group (P1), an alternative tertiary amino and tri(ethylene glycol)methyl ether group (P2), and an alternative tertiary amino and dodecyloxy group (P3). P1‘ showed intrinsic water-solubility although its quaternization degree was only 45%. Slightly blue-shifted UV−vis absorption maxima in an acidic environment (maximal Δλmax ≈ 3 nm) and obvious red-shifted absorption (maximal Δλmax ≈ 30 nm) and emission maxima (maximal Δλmax ≈ 20 nm) in an alkaline environment at pH < 13 are explained in terms of pH-induced planarization of the conjugated backbone. After the pH was increased to 14, a new absorption (λmax ≈ 478 nm) and emission (λmax ≈ 495 nm) peak appeared in the redder region and the fluorescence intensity further dramatically decreased, implying the occurrence of the conformational change from the planarization of conjugated backbone to the interchain aggregation. The fluorescence enhancement of P1‘ in an acidic environment and the fluorescence decrease of P1‘ in an alkaline environment are attributed to the pH-influenced quenching ability of the nonbonding electron pair on the nitrogen atom, which belongs to the unquaternized tertiary amino group on the side chain, and the interchain aggregation. Such pH-influenced fluorescence intensity can be efficiently buffered by adding salts at pH < 10. Although adding salts in a neutral environment only creates the planarization of PPE conjugated backbone, adding salts in an alkaline environment significantly promotes the formation of interchain aggregation. Amplified quenching of P1‘ by anionic quencher Fe(CN)64- was observed and its Ksv increased significantly after adding salts or increasing pH to 14, for example from Ksv = 9.6 × 105 M-1 at pH = 7 to 7.7 × 106 M-1 at pH = 10 when [NaCl] = 0.1 M, due to the formation of elongated π-conjugation.

The impact of water on photopolymerization kinetics of methacrylate/vinyl ether hybrid systems

AbstractReal‐time FT‐near infrared (NIR) spectroscopy was used to monitor individual monomer photopolymerization kinetics within the hybrid methacrylate/vinyl ether system composed of 2‐hydroxyethyl methacrylate and tri(ethylene glycol) methyl vinyl ether. Photoinitiation conditions have been manipulated to provide staged polymer formation of the selected hybrid systems. Significant differences were observed in the effect of water on hybrid systems with different polymerization sequence. The radical/cationic dual initiator system drastically decreased the effect of water on the vinyl ether polymerization. Even with significant water present, both the methacrylate and vinyl ether monomers can be effectively polymerized under certain initiation conditions. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Synthesis and Properties of (1-Azulenyl)di(3-indolyl)methylium Hexafluorophosphates

(l-Azulenyl)di(3-indolyl)methanes (3a-c;5a,b) were synthesized by the acid-catalyzed condensation of methyl 3-formylazulene-l-carboxylate (1) with indoles (2a-d) and converted to the corresponding (1-azulenyl)di(3-indolyl)methylium hexafluorophosphates (6a-d). On the basis of their pK R + values (∼ 13), the methyl cations (6a-d) were found to be comparably stable to tri(1-azulenyl)methyl cations.

Nanoscopic fibrous assemblies made of metallophthalocyanine-terminated amphiphilic polymers.

Atom-transfer radical polymerization (ATRP) of acrylates from the initiator-modified zinc phthalocyanine yielded amphiphilic, phthalocyanine-terminated polymers with a narrow molecular-weight distribution. The disklike phthalocyanine moiety was incorporated into one end of the polymer chain. We investigated the aggregation behavior of phthalocyanine-terminated polymers in solution and in the solid state by using UV-visible, FT-IR, differential scanning calorimetry (DSC), and temperature-controlled powder X-ray diffraction (XRD) measurements. Amphiphilic phthalocaynine-terminated polymers that possess a poly[tri(ethylene glycol)methyl ether acrylate] chain aggregate in methanol to form a physical gel. Images from atomic force microscopy (AFM) and transmission electron microscopy (TEM) indicate that the physical gel contains a dense fibrous network structure, in which the zinc phthalocyanine groups were stacked into one-dimensional columnar aggregates through intermolecular pi-pi interactions between the pi-conjugated phthalocyanines and through van der Waals interaction of alkyl chains.

Principal component analysis of FT-IR spectra for cationic photopolymerization of mixtures of two monomers

Principal component analysis (PCA) is used to analyze real-time FT-IR spectral data for cationic photopolymerizations of tri(ethylene glycol) methyl vinyl ether (TEGMVE), 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate (ECH) and their mixtures. PCA performed on different parts of the very large data set is able to extract information on subtle effects occurring in the polymerization reactions. Many of these effects are not readily apparent even from a detailed analysis of the raw spectra. The objectives of this paper are two-fold: to present important new results on the photopolymerization reaction between ECH and TEGMVE, and to illustrate the use of general PCA models to uncover subtle reaction effects occurring in time evolving reaction spectra. PCA models of the overall data set for different compositions are able to clearly separate compositional effects from time varying conversion effects. Multivariate curve resolution (MCR) on individual runs was found to provide no additional information due to rotational and intensity ambiguities that remain in spite of the imposition of different constraints. For PCA models built on runs with the same initial monomer composition ratios, loading plots and contribution plots are used to obtain a much clearer interpretation of the reactions involved in the polymerization. Furthermore, important structural differences occurring among “replicate” runs are uncovered providing further insight into the reaction mechanisms, and into reasons for batch-to-batch inconsistencies that may occur in a manufacturing process.

The polymer electrolyte based on polysiloxane containing both alkyl cyanide and oligo ethylene oxide pendants

The monomers, (3-cyanopropyl) methylsiloxane cyclics (D4CN) and (3-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)propyl) methylsiloxane cyclics (D4TEG) were prepared by a hydrosilylation reaction of 2,4,6,8-tetramethylcyclotetrasiloxane (D4H) with allyl cyanide and tri(ethylene glycol) methyl allyl ether (allyl TEG), respectively, in toluene using a platinum(0)-1,3-divinyl-1,1,3,3-tetramethyl disiloxane complex as the catalyst. The new crosslinkable polymers with alkyl cyanide and ethylene oxide groups as the pendent were synthesized by ring opening polymerization and characterized by GPC and 1H NMR. And then, the crosslinked solid polymer electrolyte was prepared by UV radiation curing. The conductivities of samples were measured by impedance spectroscopy using an indium–tin oxide (ITO) electrode. As the results, the maximum ionic conductivities of the polymer were 1.15 × 10 −5 S cm −1 at 20 °C and 1 × 10 −4 S cm −1 at 60 °C. The electrolyte was stable electrochemically to 5 V versus Li +/Li at room temperature.

A New, One Pot Synthesis of Alkylated Methyl Tri- and Tetracarboxylate Derivatives­ by Nitrolkanes

The reaction of nitroalkanes with trimethyl trans-aconitate in acetonitrile, in the presence of DBU as base, allows the one pot formation of alkylated methyl tri- and tetralkanoate derivatives via base induced nitrous acid elimination. The title compounds can also be obtained, in one flask, starting with the reaction of methyl nitroacetate with dimethyl maleate, followed by the addition, in the same flask of the nitroalkane.

Synthesis and Reactivity of Alkyl, Hydride, and Silyl Derivatives of the (Terphenyl)imido Fragments Cp*(ArMesN)Ta (Cp* = η5-C5Me5; ArMes = 2,6-(2,4,6-Me3C6H2)2C6H3) and Cp*(ArTripN)Ta (ArTrip = 2,6-(2,4,6-iPr3C6H2)2C6H3)

The syntheses and reactivities of tantalum alkyl, hydride, and silyl complexes containing a sterically demanding, mixed Cp*-(terphenyl)imido (Cp* = η5-C5Me5) ligand set are reported. The dichloride complex Cp*(ArMesN)TaCl2 (1), prepared by the reaction of ArMesNHLi (ArMes = 2,6-(2,4,6-Me3C6H2)2C6H3) with Cp*TaCl4 in the presence of a large excess of NEt3, was structurally characterized. Complex 1 reacted readily with KSi(SiMe3)3 to give the silyl chloride compound Cp*(ArMesN)Ta[Si(SiMe3)3]Cl (2), and with MeLi (2 equiv) to yield the dimethyl complex Cp*(ArMesN)TaMe2 (4). Compound 2 reacted with PhSiH3 via the intermediate complex Cp*(ArMesN)Ta(SiH2Ph)Cl to give the hydrido chloride complex Cp*(ArMesN)Ta(H)Cl (3). While the analogous compound of the [DippN]2- (Dipp = 2,6-iPr2C6H3) ligand is a dimer with bridging hydrides, compound 3 contains a terminal hydride, as indicated by the downfield 1H NMR resonance of the hydride ligand (15.28 ppm). Treatment of 4 with AgOTf (OTf = OSO2CF3) provided the methyl tri...

Kinetics studies of hybrid structure formation by controlled photopolymerization

Real-time FT-NIR spectroscopy was used to monitor the individual monomer photopolymerization kinetics within the hybrid methacrylate/vinyl ether system composed of 2-phenoxyethyl methacrylate and tri(ethylene glycol) methyl vinyl ether. Photopolymerization processing conditions, such as light intensity, photoinitiator type (both free radical and cationic) and initiator ratios and concentrations, that provide preferential direction of polymer formation based on individual monomer photopolymerization kinetics and overall conversion have been evaluated. Single source UV-light irradiation was employed to produce either single or dual-stage hybrid polymerization, validating the potential of one-step, one-pot methodology for initiating stage-curable polymerizations.

Prediction of the disinfection and oxidation efficiency of full-scale ozone reactors

The efficiency of a two-step ozonation with regard to disinfection and oxidation of micropollutants; was assessed for a river-water treatment plant (Limmat River, Zurich, Switzerland). The assessment was based on laboratory experiments to estimate transient ozone and OH radical concentrations coupled with hydraulic modelling of the ozone reactors. The laboratory experiments were performed for various temperatures, ozone dosages and pretreatments to mimic the full-scale treatment. The hydraulics were determined by a conservative tracer test. The kinetic data for disinfection and oxidation were taken from the literature. The inactivation of microorganisms (Cryptosporidium parvum oocysts, Bacillus subtilis spores, Giardia lamblia cysts and polio virus) was more critical at low temperature (5degreesC) than at high temperature (20degreesC). For Cryptosporidium parvum oocysts it was calculated to be less than 1 log for the two ozonation steps, and an overall ozone dose of 1.5 mg/l (5degreesC). For the same microorganism it was >3.5-log inactivation at 20degreesC. For other microorganisms, the calculated inactivation was greater than or equal to2 log (5degreesC) with B. subtilis spores being the most resistant. The oxidation of micropollutants was much less affected by variations in the temperature. The fraction of oxidation increased in the following order: between 15 and 25% of tetrachloroethene, 15 and 25% of methyl tertiary butyl ether, 30 and 40% of atrazine, 80 and 90% of p-xylene and between 97 and 100% of trim ethyl benzene were oxidized. For the oxidation of methyl tertiary butyl ether, the formation of degradation products was modelled in the pre-ozonation step. For all investigated treatment conditions the overall bromate formation was less than or equal to2.5 mug/l.

Synthesis of New Surface-Active β-Amino Amides, Agents for Fixation of Dyes on Cotton Fibers, from N -[Tri(hydroxymethyl)methyl]acrylamide

Amines containing amido and hydroxy groups were prepared. Their surface activity was studied, and the possibility of their use as cotton fiber modifiers was examined.

Syntheses and structures of lithium cyanocuprates containing the C(SiMe3)3, C(SiMe3)2(SiMe2NMe2) and C(SiMe3)(SiMe2OMe)2 groups

The ‘lower order’ lithium cyanocuprates [Li(thf)2NCCu{C(SiMe3)3}]2 (1d), [Li(thf)2NCCu{C(SiMe3)2(SiMe2NMe2)}]2 (1e) and [Li(thf)NCCu{C(SiMe3)(SiMe2OMe)2}]2 (3) have been obtained from the reactions between copper(I) cyanide and the corresponding organolithium compounds. The compounds 1d and 1e have molecular structures containing four-membered Li2N2 rings but in 3 the lithium is coordinated by the methoxy groups of the ligand and almost linear LiNCCuC sequences are incorporated into fourteen-membered rings. Attempts to make ‘higher order’ cyanocuprates containing tri(organosilyl)methyl groups were unsuccessful and no reactions were observed when the cyanocuprate 1d was treated with alkyl halides or enones.

Generation, Reactions, and Kinetics of Di(naphthyl)carbenes: Effects of the Methyl Group

A series of di(naphthyl)carbenes (DNCs) having methyl groups on aromatic rings were generated by photolysis of the corresponding diazo precursors and studied not only by product analysis, but also by spectroscopic means. “Parent” triplet α-DNC was shown to have a half-life of 70 ms, which is some 30 times larger than that of triplet diphenylcarbene (3DPC), whereas parent triplet β-DNC was 2 orders of magnitude shorter-lived than the α-isomer. The lifetimes of triplet DNCs were significantly increased by introducing methyl groups near the carbene center. Thus, 3α-DNC, which has four methyl groups at 2,2‘,4,4‘-positions, was shown to have a half-life of 100 ms, and the replacement of the two methyl groups at the 2,2‘-positions of this carbene with tri(deuterio)methyl groups resulted in an increase of the lifetime by approximately 3 times by quenching the intramolecular H transfer from the methyl groups to the carbene center leading to o-quinoid compounds. The results are discussed in terms of the counteracting effects of electronic properties stabilizing the singlet state and steric factors favoring the triplet and compared with similar studies with 3DPCs.

Attachment to manganese or cobalt of a bulky tri(organosilyl)methyl ligand containing an NMe 2 or an OMe donor group

The organolithium compound L i(THF) 2{C(SiMe 3) 2(SiMe 2N Me 2)} reacted with one equivalent of MnCl 2 to give [ Mn(μ-Cl){C(SiMe 3) 2(SiMe 2N Me 2)}] 2 ( 4) and with 0.5 equivalent of MnCl 2 to give Mn{C(SiMe 3) 2(SiMe 2NMe 2)} 2 together with a small amount of the Mn III compound [ Mn(μ-O){C(SiMe 3) 2(SiMe 2N Me 2)}] 2 ( 6) formed by adventitious admission of air. With CoBr 2, the compound [ Co(μ-Br){C(SiMe 3) 2(SiMe 2N Me 2)}] 2 ( 7) was obtained. The reaction between the lithium compound Li(THF) 2{C(SiMe 3) 2(SiMe 2O Me)} and MnCl 2 in THF gave [ Mn(THF)(μ-Cl){C(SiMe 3) 2(SiMe 2O Me)}] 2 ( 5). The crystal structures of compounds 4, 5, 6 and 7 were determined. Compounds 4 and 5 are the first manganese analogues of Grignard reagents containing MnC σ-bonds to be characterised in the solid state.