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Cetyl Trimethyl Ammonium Bromide (cetyl + trimethyl_ammonium_bromide)
Selected AbstractsSynthesis and comparative physicochemical investigation of partly aromatic cardo copolyestersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007N. B. Joshi Abstract Copolyesters were synthesized through the condensation of 0.0025 mol of 1,1,-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 0.0025 mol of ethylene glycol/propylene glycol/1,4-butanediol/1,6-hexane diol, and 0.005 mol of terephthaloyl chloride with water/chloroform (4:1 v/v) as an interphase, 0.0125 mol of sodium hydroxide as an acid acceptor, and 50 mg of cetyl trimethyl ammonium bromide as an emulsifier. The reaction time and temperature were 2 h and 0°C, respectively. The yields of the copolyesters were 81,96%. The structures of the copolyesters were supported by Fourier transform infrared and 1H-NMR spectral data and were characterized with the solution viscosity and density by a floatation method (1.1011,1.2697 g/cm3). Both the intrinsic viscosity and density of the copolyesters decreased with the nature and alkyl chain length of the diol. The copolyesters possessed fairly good hydrolytic stability against water and 10% solutions of acids, alkalis, and salts at room temperature. The copolyesters possessed moderate-to-good tensile strength (11,37.5 MPa), good-to-excellent electric strength (19,45.6 kV/mm), excellent volume resistivity (3.8 × 1015 to 2.56 × 1017 , cm), and high glass-transition temperatures (148,195°C) and were thermally stable up to about 408,427°C in a nitrogen atmosphere; they followed single-step degradation kinetics involving 38,58% weight losses and 34,59% residues. The copolyesters followed 2.6,2.9-order degradation kinetics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Kinetic study on the prooxidative effect of vitamin C on the autoxidation of glycerol trioleate in micellesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2006Zai-Qun Liu Abstract Vitamin C (L -ascorbic acid) protects human health by scavenging toxic free radicals and other reactive oxygen species formed in cell metabolism. The surplus supplementation of vitamin C, however, may be harmful to health because the level of 8-oxoguanine and 8-oxoadenine in lymphocyte DNA varies remarkably. In the process of the kinetic investigation on the 2,2,-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced autoxidation of glycerol trioleate (GtH) in the micelles of cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS) and Triton X-100, the addition of vitamin C accelerates the autoxidation of GtH even in the absence of the free radical initiator, AAPH. The initiating rate, Ri, of vitamin C (VC)-induced autoxidation of GtH is related to the micelle charge, i.e. Ri,=,14.4,×,10,6 [VC] s,1 in SDS (anionic micelle), Ri,=,1961,×,10,6 [VC] s,1 in Triton X-100 (neutral micelle) and Ri is a maximum in CTAB (cationic micelle) when the vitamin C concentration is ,300,µM. Thus, vitamin C can initiate autoxidation of GtH in micelles, especially in the neutral one. Moreover, the attempt to explore whether ,-tocopherol (TocH) could rectify vitamin C-induced autoxidation of GtH leads us to find that the rate constant of TocH reacting with the anionic radical of vitamin C (VC.,), k,inh, is ,103M,1,s,1, which is less than that of the ,-tocopherol radical (Toc.) with vitamin C (kinh,=,,105,M,1,s,1). Thus, the equilibrium constant of the reaction Toc.+VC,,TocH+VC., is prone strongly to the regeneration of Toc. by vitamin C rather than the reverse reaction. Copyright © 2006 John Wiley & Sons, Ltd. [source] Kinetics of the M-Intermediate in the Photocycle of Bacteriorhodopsin upon Chemical Modification with SurfactantsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2010Li-Kang Chu The spectroscopic and kinetic studies of the interaction between bacteriorhodopsin in the M-intermediate and several surfactants (cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, diethylene glycol mono- n -hexyl ether, ethylene glycol mono- n -hexyl ether, sodium 1-decanesulfonate and sodium 1-heptanesulfonate) have been investigated using steady-state UV,VIS spectrometry and time-resolved absorption techniques. The steady-state spectral results show that bR retains its trimeric state. Time-resolved observations indicate that the rate of deprotonation of the protonated Schiff base increases in the presence of the cationic surfactants, whereas insignificant changes are observed in the neutral or anionic surfactants. The rate of the reprotonation of the Schiff base in the transition M , N is accelerated in anionic and neutral surfactants, but is decelerated in the presence of the cationic surfactants. Surfactants with a longer hydrocarbon tail have a greater effect on the kinetics when compared with surfactants having shorter hydrocarbon tails. The opposite effect is observed when the hydrophilic head of the surfactants contains opposite charges. These distinct kinetics are discussed in terms of the difference in the modified surface hydrophilicity of the bR and the possible protein configurational changes upon surfactant treatments. [source] Effect of clay/water ratio during bentonite clay organophilization on the characteristics of the organobentonites and its polypropylene nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 9 2009Suédina M.L. Silva A sodium bentonite (montmorillonite-based layered silicate clay) was organically modified with cetyl trimethyl ammonium bromide (cetrimide), using different clay/water ratios,but the same clay/cetrimide ratio,to suspend the bentonite clay and perform its organophilization. Infrared spectroscopy and thermogravimetric analysis indicated the incorporation of organic modifier into the bentonite. Wide-angle X-ray scattering showed that the incorporation of surfactant significantly increased the interlayer spacing in the bentonite for all concentrations studied. It was found that clay/water ratio employed during the modification affects neither the amount of organic salt incorporated nor the interlayer spacing in the organobentonites, but influences its degree of structural disorder. Lower clay/water ratios resulted in a more disorderly structure, as established by the decrease of the areas under the X-ray peaks as the clay/water ratio diminishes. The modified bentonites were melt compounded with maleic anhydride-grafted polypropylene. X-ray diffraction patterns of the hybrids revealed that the more disorderly organobentonites were better dispersed in the polymer matrix, indicating that, in the present system, the structure of polymer nanocomposites obtained were affected by the clay/water ratio used in organobentonite preparation. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Preparation of Mesoporous Molecular Sieves Al-MSU-S Using Ionic Liquids as TemplateCHINESE JOURNAL OF CHEMISTRY, Issue 10 2006Xin-Yu Yu Abstract Mesoporous molecular sieves Al-MSU-S has been prepared from the precursor of zeolite Y using ionic liquids 1-hexadecane-3-methylimidazolium bromide (CMIMB) as a template in basic medium, which exhibited larger pore diameter, pore volume and surface area than that synthesized using cetyl trimethyl ammonium bromide (CTAB) template. [source] | |||||||||||||