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Phase Behaviour (phase + behaviour)
Selected AbstractsFTIR Microanalysis and Phase Behaviour of Ethylene/1-Hexene Random CopolymersMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2007Mariano Pracella Abstract Ethylene/1-hexene random copolymers with 1-hexene content in the range of 1,5 mol-%, synthesised in the presence of new heterogeneous catalyst systems based on bis-carboxylato and -bis-chloro-carboxylato titanium chelate complexes, have been characterised by FTIR microspectroscopy (FTIR-M), DSC calorimetry and X-ray scattering. The co-monomer content and sequence distribution in the various samples were determined by means of both FTIR-M and 13C NMR spectroscopy. The deformation bands of methyl groups in the region of 1,400,1,330 cm,1 were used for the structural analysis of these copolymers. The effect of composition on the crystallinity and phase transitions of copolymers was analysed both in 1,500,1,300 and 760,690 cm,1 frequency ranges as a function of the annealing temperature. A neat variation of the absorbance ratio of methyl band at 1,378 cm,1 was recorded between 110 and 130,°C corresponding to the melting range of the copolymer crystals. The crystallisation behaviour of the copolymers was examined by DSC in dynamic and isothermal conditions; the isothermal kinetics were analysed according to the Avrami model. A marked decrease in the bulk crystallisation rate, accompanied by changes in the nucleation and growth of crystals, was found with an increase in the co-monomer content. The melting behaviour of isothermally crystallised samples was also investigated and the melting temperatures of the copolymers at equilibrium conditions were related to the composition; the experimental data were consistent with the Flory exclusion model of side branches from the crystalline phase. The lowering of crystal growth rate in the copolymers has been accounted for by an increase in the free energy of formation of critical size nuclei due to the effect of the side branches. [source] Synchrotron X-ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p,-bibenzoate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2003Ernesto Pérez Abstract Time-resolved synchrotron X-ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p,-bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110,°C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained. Scattering profiles corresponding to sample PDEB85 in a melting experiment. [source] Phase behaviour of microemulsions with lubricant base oil as the oil phaseLUBRICATION SCIENCE, Issue 7 2009Ya Lu Abstract Appropriate surfactants and co-surfactants were chosen to prepare a microemulsion system with lubricant base oil as the oil phase. The phase behaviour of the microemulsion at different temperatures and at different oil/water mass ratios was assessed on the basis of conductivity measurements. Microemulsions and a bi-continuous microstructure were obtained when the oil/water mass ratio was below 0.33. An analysis of the conductivity behaviour of the microemulsions revealed that different conductive mechanisms are operative at different water contents. Activation energies (,E) were determined. The results showed that ,E increases with increasing water content. The data and the derived relationship provided a basis for preparing metalworking microemulsions. Copyright © 2009 John Wiley & Sons, Ltd. [source] Phase behaviour of methylcellulose,poly(acrylic acid) blends and preparation of related hydrophilic filmsPOLYMER INTERNATIONAL, Issue 1 2003Vitaliy V Khutoryanskiy Abstract The phase behavior of methylcellulose-poly(acrylic acid) mixtures was studied in aqueous solution. It was shown that the complexation between the two polymers decreases considerably the cloud-point of methylcellulose. The addition of inorganic salts shifts the critical pH values toward a higher pH region. Films were prepared based on methylcellulose-poly(acrylic acid) blends and were analyzed by dynamic mechanical thermal analysis, scanning electron microscopy and thermal gravimetric analysis. The miscibility between the two polymers in the films was shown. It was found that the thermal treatment of the films leads to their cross-linking with the formation of materials swellable both in water and ethanol. © 2003 Society of Chemical Industry [source] The assembly factor P17 from bacteriophage PRD1 interacts with positively charged lipid membranesFEBS JOURNAL, Issue 20 2000Juha M. Holopainen The interactions of the assembly factor P17 of bacteriophage PRD1 with liposomes were investigated by static light scattering, fluorescence spectroscopy, and differential scanning calorimetry. Our data show that P17 binds to positively charged large unilamellar vesicles composed of the zwitterionic 1-palmitoyl-2-oleoyl-phosphatidylcholine and sphingosine, whereas only a weak interaction is evident for 1-palmitoyl-2-oleoyl-phosphatidylcholine vesicles. P17 does not bind to negatively charged membranes composed of 1-palmitoyl-2-oleoyl-phosphatidylglycerol and 1-palmitoyl-2-oleoyl-phosphatidylcholine. Our differential scanning calorimetry results reveal that P17 slightly perturbs the phase behaviour of neutral phosphatidylcholine and negatively charged multilamellar vesicles. In contrast, the phase transition temperature of positively charged dimyristoylphosphatidylcholine/sphingosine multilamellar vesicles (molar ratio 9 : 1, respectively) is increased by approximately 2.4 °C and the half width of the enthalpy peak broadened from 1.9 to 5.6 °C in the presence of P17 (protein : lipid molar ratio 1 : 47). Moreover, the enthalpy peak is asymmetrical, suggesting that lipid phase separation is induced by P17. Based on the far-UV CD spectra, the ,-helicity of P17 increases upon binding to positively charged micelles composed of Triton X-100 and sphingosine. We propose that P17 can interact with positively charged lipid membranes and that this binding induces a structural change on P17 to a more tightly packed and ordered structure. [source] Organized Nanostructured Complexes of Polyoxometalates and Surfactants that Exhibit Photoluminescence and ElectrochromismADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Tierui Zhang Abstract A variety of functional nanostructured organic/inorganic hybrid materials from the europium-exchanged derivative of a Preyssler-type polyoxometalate (POM), [EuP5W30O110]12,, and functional organic surfactants were prepared by the ionic self-assembly (ISA) route. The effect of organic surfactants on the structure, photoluminescent, electrochemical and electrochromic properties of the POM anions was investigated in detail. All obtained hybrid materials are amphotropic, i.e., exhibit both thermotropic and lyotropic liquid-crystalline phase behaviour. Investigations of their photophysical properties have shown that the interactions of the various surfactants with the polyanions influence the coordination environments and site symmetry of Eu3+ in different ways. The functional groups in the organic surfactants significantly influence the electrochromic properties and photoluminescence of POMs. Different from normal and pyridine-containing complexes, no photoluminescence and no electrochromism were observed from the ferrocene-containing complexes. This may be explained in view of charge transfer between the POM anion and the ferrocenyl group. [source] Formation of Lipid Emulsions and Clear Gels by Liquid Crystal EmulsificationINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2007T. Suzuki Recently developed emulsion technologies for the formation of fine emulsions, lipid emulsions and clear gels by liquid crystal emulsification were reviewed. As a basic information on liquid crystal emulsification, the structures and characteristic behaviours of lyotropic liquid crystals were summarized. Formation of a liquid crystalline phase was often seen in emulsions and biological systems. The significance of liquid crystal formation during emulsification was analysed by comparing the states and stabilities of emulsions prepared by different processes. Then uses of liquid crystals for formation of the characteristic emulsions and gels were also discussed. In liquid crystal emulsification, an oil phase is dispersed directly into the lamellar liquid-crystalline phase composed of surfactant, glycerol and water to prepare a gel-like oil-in-liquid crystal emulsion. This is followed by dilution with the remaining water to produce an emulsion. From the phase behaviour during emulsification and analysis of the local motion of the liquid crystal membrane by fluorometry, it was confirmed that the interaction between surfactant and a polyol molecule such as glycerol promotes hydrogen bonding and enhances the strength of the lamellar liquid crystal membranes, which results in the formation of oil-in-liquid crystal emulsions. The interaction between the liquid crystal and oil was analysed from the changes in molecular motion of the membrane at the oil-liquid crystal interface using the spin label technique of electron spin resonance (ESR). The fluidity of the liquid crystal membrane did not change when oil was added, and therefore oil-in-liquid crystal emulsions of various oils were prepared by the identical process. This lack of dependence of the liquid crystal membrane on oil results in the unique properties of liquid crystal emulsification, which can be used for oils of various polarity and different molecular constituents. When a self-organizing artificial stratum corneum lipid containing pseudo-ceramide was used as a principal component of the oil, a multilamellar emulsion of concentric lamellar structure was formed. The multilamellar emulsion supplements the physiological function of stratum corneum by the identical mechanism as natural intercellular lipids. High-pressure treatment of the lipid emulsion produced a gel-like emulsion crystal, in which the homogeneous nanoemulsion droplets were arranged in a hexagonal array. This review paper was presented at the Conference of the Asian Societies of Cosmetic Scientists 2005 in Bangkok. [source] Performance analysis of a variable structure controller for power regulation of WECS operating in the stall regionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2001H. De Battista Abstract This paper deals with power regulation in variable speed wind energy conversion systems. The importance of power control in the stall region is stressed. This mode of operation is characterized by a non-minimum phase behaviour. A variable structure controller is described that provides stability by means of speed feedback and is robust to grid disturbances and model uncertainties. Performance of the controller is investigated. A compromise arises in the design of the speed feedback gain between high and low frequency wind components rejection. Furthermore, a cut-off frequency of the wind velocity measurement is obtained that minimizes the effect of turbulence on power regulation. Simulation results are presented, corroborating the features of the control strategy. Copyright © 2001 John Wiley & Sons, Ltd. [source] Temperature and pressure effects on structural formations in a ternary microemulsionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2000M. Nagao Small angle neutron scattering experiments were conducted on a temperature-induced phase transition in a ternary microemulsion composed of AOT (dioctyl sulfosuccinate sodium salt), D2 O and n -decane and the results were compared with those of pressure-induced one. Although the static features of both the temperature- and the pressure-induced phase behaviour were similar, a temperature dependence of its characteristic repeat distance at high temperature was quite different from a pressure dependence of that at high pressure. Neutron spin echo experiments were also performed on both the phase transitions. The dynamics of the high temperature phase was different from that of the high pressure phase. These results indicated that the effect of pressure on the structural formation was different from that of temperature. [source] Synchrotron X-ray and DSC Studies of the Phase Behaviour of Poly(diethylene glycol p,p,-bibenzoate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2003Ernesto Pérez Abstract Time-resolved synchrotron X-ray and DSC experiments were applied to investigate the phase behaviour of poly(diethylene glycol p,p,-bibenzoate), PDEB. The DSC results are indicative of the formation of a smectic mesophase, previously identified as a SmCA type, which can be easily quenched down to room temperature. However, the synchrotron results show that the SmCA phase undergoes some kind of ordering or transformation at temperatures below 110,°C. Moreover, the annealing of PDEB at temperatures above Tg for sufficiently long times leads to the formation of a highly ordered structure, although very thin crystals and low crystallinities are obtained. Scattering profiles corresponding to sample PDEB85 in a melting experiment. [source] EPR studies of the dynamics and phase behaviour of dithiadiazolyl radicals derived from mesogenic precursorsMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2009Jeremy M. Rawson Abstract A series of liquid-crystalline materials based on 4-substituted cyanobiphenyls, RC6H4C6H4CN (R = C5H11, C6H13, C7H15, C8H17 and C12H25, commonly referred to as 5CB, 6CB, 7CB, 8CB and 12CB, respectively) were functionalised to give the corresponding dithiadiazolyl organic radicals RC6H4C6H4CNSSN, (compounds 1,, 2,, 3,, 4, and 5,, respectively). EPR spectra of n -C12H25C6H4C6H4CNSSN, (5,) reveal that it adopts a dimeric diamagnetic structure in the solid state with a small number of paramagnetic defect sites. Variable temperature electron paramagnetic resonance (EPR) studies reveal a thermally activated rotation about the molecular long axis at temperatures above 314 K. The energy barrier to rotation about the phenylene,dithiadiazolyl bond was estimated as 25 kJ mol,1 using density functional theory (DFT). At elevated temperatures thermal annealing was also observed, quenching the sample's paramagnetism. Copyright © 2008 John Wiley & Sons, Ltd. [source] Self-assembled structures in blends of disordered and lamellar block copolymers: SAXS, SANS and TEM studyPOLYMER INTERNATIONAL, Issue 1 2009Jaroslav Holoubek Abstract BACKGROUND: The phase behaviour of copolymers and their blends is of great interest due to the phase transitions, self-assembly and formation of ordered structures. Phenomena associated with the microdomain morphology of parent copolymers and phase behaviour in blends of deuterated block copolymers of polystyrene (PS) and poly(methyl methacrylate) (PMMA), i.e. (dPS- block - dPMMA)1/(dPS- block -PMMA)2, were investigated using small-angle X-ray scattering, small-angle neutron scattering and transmission electron microscopy as a function of molecular weight, concentration of added copolymers and temperature. RESULTS: Binary blends of the diblock copolymers having different molecular weights and different original micromorphology (one copolymer was in a disordered state and the others were of lamellar phase) were prepared by a solution-cast process. The blends were found to be completely miscible on the molecular level at all compositions, if their molecular weight ratio was smaller than about 5. The domain spacing D of the blends can be scaled with Mn by D , Mn2/3 as predicted by a previously published postulate (originally suggested and proved for blends of lamellar polystyrene- block -polyisoprene copolymers). CONCLUSIONS: The criterion for forming a single-domain morphology (molecularly mixed blend) taking into account the different solubilization of copolymer blocks has been applied to explain the changes in microdomain morphology during the self-assembling process in two copolymer blends. Evidently the criterion, suggested originally for blends of lamellar polystyrene- block -polyisoprene copolymers, can be employed to a much broader range of block copolymer blends. Copyright © 2008 Society of Chemical Industry [source] Copolyesters of hydroxyphenylalkanoic acids: synthesis and thermal properties of poly{(4-oxybenzoate)- co -[8-(3-oxyphenyl)octanoate]} and poly{(3-bromo-4-oxybenzoate)- co -[8-(3-oxyphenyl)octanoate]}POLYMER INTERNATIONAL, Issue 6 2002Shiney Abraham Abstract Copolyesters of 8-(3-hydroxyphenyl)octanoic acid (HPOA), a monomer with kink and flexible segment derived from cardanol, and 4-hydroxybenzoic acid (HBA) or its brominated derivative, 3-bromo-4-hydroxybenzoic acid (BrHBA), were synthesized by acidolysis melt polycondensation of the in situ generated acetoxyderivative in the presence of magnesium acetate as catalyst by a one-pot method and characterized. The formation of the copolyester was confirmed by elemental analysis, FTIR and 1H NMR spectroscopy. These polymers were highly insoluble in most solvents except highly polar solvents, such as trifluoroacetic acid. The inherent viscosities of the soluble polymers were in the range of 0.8,1.1,dlg,1. The thermal and phase behaviour of the copolyesters were studied by DSC and polarized light microscopy. Poly{(4-oxybenzoate)- co -[8-(3-oxyphenyl)octanoate]} with 50 mole% of HPOA showed a birefringent melt with opalescence and a worm-like texture of a nematic phase. The effect of bromine substitution in the analogue poly{(3-bromo-4-oxybenzoate)- co -[8-(3-oxyphenyl)octanoate]} was evident when it showed a lower transition with minimum 45% Br-HBA at 225,°C showing enhanced melt processability. These copolymers, with hydrolytically degradable aliphatic carbonyl group and better crystallinity compared to poly(hydroxyalkanoate)s, are interesting in possible biomedical applications. © 2002 Society of Chemical Industry [source] Low and Wide Phase Transition Temperature Dimesogenic Compounds Consisting of a Cholesteryl and 4-(trans -4- n -Alkylcyclohexyl)phenoxy MesogensCHINESE JOURNAL OF CHEMISTRY, Issue 3 2006Chun-Bo Zhang Abstract Unsymmetrical dimesogenic compounds with cholesteryl and 4-(trans -4- n -alkylcyclohexyl)phenoxy parts were synthesized by condensation of cholester-3-yl 6-bromohexanoate with appropriate 4-(trans -4- n -alkylcyclohexyl)- phenols. Structures and thermal phase behaviour of these dimesogenic compounds have been confirmed by IR, 1H NMR, elemental analysis, DSC, polarity microscopy and XRD measurements. Their thermal phase behaviour was significantly different with that of other cholesterol-based dimesogens while they exhibited low and wide phase transition temperature. [source] | ||||||||||||||||