Home About us Contact
|
Home About us Contact | ||
|
|
||
Low Boiling Points (low + boiling_point)
Selected AbstractsThe essential oil co-distillation by superheated vapour of organic solvents from aromatic plantsFLAVOUR AND FRAGRANCE JOURNAL, Issue 5 2001Josip Masteli Abstract A method of essential oil co-distillation by superheated vapour of solvents was developed and the apparatus was presented. As suitable solvents, pentane and ether (inert solvent with low boiling point) were used. The method was tested on sage, Salvia officinalis L., as an aromatic plant. The essential oil of this plant was also isolated by hydrodistillation as a standard method. The isolated volatiles obtained by two methods were analysed using gas chromatography (GC) and gas chromatography,mass spectrometry (GC,MS). The obtained results were compared. This method of distillation enables safe isolation of monoterpene and sesquiterpene compounds, as well as hydrodistillation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthesis of CdSe quantum dots with luminescence in the violet region of the solar spectrumLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2010Nisha Shukla Abstract We have designed a simple, one-step synthesis of CdSe quantum dots with photoluminescence frequencies ranging from the red through to the violet region of the solar spectrum. The photoluminescence peaks have FWHM of 30 nm indicating absorption over a narrow range of wavelengths. The effect of solvent type and solvent boiling point on the physical and photoluminescence properties of the quantum dots has been studied. High boiling point, non-polar solvents shift the photoluminescence peak to longer wavelengths and low boiling point, polar solvents shift the photoluminescence peak to shorter wavelengths. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis and characterization of hyperbranched polymers with increased chemical versatility for imprint lithographic resistsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Anzar Khan Abstract Hyperbranched polymers were prepared from a variety of mono- and difunctional monomers and used in the development of novel UV-imprint lithography (UV-IL) resists. The unique physical and chemical properties of these hyperbranched materials significantly increase the range of molecular systems that could be imprinted. Traditional challenges, such as the use of monomers that have low boiling points or the use of insoluble/highly crystalline momomers, are overcome by the preparation of hyperbranched polymers that incorporate these repeat units. In addition, the low viscosity of the hyperbranched macromolecules and the large number of reactive chain ends overcome many difficulties that are traditionally associated with the use of polymeric materials as imprint resists. Hyperbranched polymers containing up to 12 mol % pendant vinyl groups, needed for secondary crosslinking during imprinting, were prepared with a wide range of repeat unit structures and successfully imprinted with features from tens of microns to , 100 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6238,6254, 2008 [source] Liquid Chromatographic Separation of Olefin Oligomers and its Relation to Separation of Polyolefins , an OverviewMACROMOLECULAR SYMPOSIA, Issue 1 2009Tibor Macko Abstract Summary: Linear and branched alkanes are oligomers of polyethylene. Alkanes with higher molar masses are called waxes. These substances are widely used as fuels, oils, lubricants, etc. and for these reasons many groups have tried to analyse, separate and characterise alkanes by various methods, including liquid chromatography. Alkanes may be separated according to their size in solution by SEC. In addition to chromatographic systems separating in the SEC mode, various sorbent-solvent systems have been published, where alkanes have been separated one from another by adsorption and/or precipitation mechanism. The mobile phase is either a non-polar solvent or a polar solvent or a mixture of a solvent and a non-solvent for alkanes. Even near critical conditions, which have several advantages for applications of HPLC in polymer analysis, have been identified for alkanes. Moreover, selective separations of branched alkanes according to their structure have been published. In the majority of these published studies, solvents with low boiling points have been used as the mobile phases, which do not allow dissolution of crystalline polyolefins at atmospheric pressure. However, taking into account experiences with the separation of alkanes, new HPLC systems for the separation of polyolefins may be developed. This is a major challenge and first results are presented in this contribution. [source] Investigation of redox initiators for free radical frontal polymerizationPOLYMER INTERNATIONAL, Issue 8 2009Huan Yu Abstract BACKGROUND: The reaction temperature for frontal polymerization (FP) initiated by redox initiators can be greatly decreased compared with FP initiated by peroxide initiator and disulfide initiator. We report the synthesis of poly(hydroxyethyl acrylate)s via free radical FP using benzoyl peroxide (BPO)/N,N -dimethylaniline (DMA) and ammonium persulfate (APS)/N,N,N,,N,-tetramethylethylenediamine (TMEDA) couples as redox initiators at ambient pressure. RESULTS: The results show that unlike the phenomenon of bubbles and ,fingers' when using BPO alone, a self-sustaining and stable front can be obtained when the [DMA]/[BPO] ratio is higher than 1 (mol/mol). A slight increase of the DMA (or TMEDA) reductant concentration causes a marked decrease of front temperature to 53 °C (or 61 °C). CONCLUSION: We investigated the effects of the ratio of the oxidant to the reductant and the initiator and monomer concentrations on certain parameters of FP: formation of bubbles, front velocity and front temperature. This opens the way to the potential development of FP using more appropriate monomers with low boiling points. Copyright © 2009 Society of Chemical Industry [source] | |||||||||||||