共查询到20条相似文献,搜索用时 15 毫秒
1.
A. A. Gavrilov Ya. V. Kudryavtsev P. G. Khalatur A. V. Chertovich 《Polymer Science Series A》2011,53(9):827-836
The dissipative particle dynamics method and parallel computing are employed for computer simulation of phase separation in
melts of regular and random (Markovian) AB multiblock copolymers of symmetric compositions. For the first time, it is shown
that, as the Flory-Huggins parameter χ is increased, lamellar microstructures are formed in all these systems. At preset block
length M, the microstructures arise in regular copolymers at lower χ values than those in random copolymers, while the formed lamellas
are narrower and have smaller amounts of defects. At χM > 100, a superstrong segregation regime develops in the regular copolymers. In random copolymer melts, bicontinuous structures
are observed for a long time; in the long run, they are likewise transformed into lamellar structures whose imperfection substantially
increases with M. 相似文献
2.
A. V. Knyazev N. G. Chernorukov N. Yu. Kuznetsov 《Russian Journal of Inorganic Chemistry》2011,56(12):1875-1878
Compounds of composition Li
x
Na1 − x
VWO6 (0 ≤ x ≤ 1), which are synthetic analogues of brannerite-type minerals, were produced for the first time by solid-state synthesis
at high temperatures. The structure of the compounds and their unlimited miscibility in the solid phase in the LiVWO6-NaVWO6 binary system were determined by X-ray diffraction. The phase equilibrium diagram was studied by differential thermal analysis
together with thermodynamic modeling. It was found that the system under investigation is described by the regular solid solutions
model. 相似文献
3.
Alexey Bobrovsky Valery Shibaev Vera Hamplova Miroslav Kaspar Milada Glogarova 《Monatshefte für Chemie / Chemical Monthly》2009,140(7):789-799
Abstract A novel chiral–photochromic side-chain polyacrylate with azobenzene fragments in the side groups has been synthesised. It
was shown that the polymer forms a smectic phase and a cholesteric supramolecular helical structure with selective light reflection
in IR spectral range. Thin spin-coated films of the polymer were prepared and their photooptical and chirooptical properties
were studied in detail. It was found that UV irradiation of the films led to E–Z isomerization of the azobenzene moieties with high conversion, which is dependent on thermal prehistory of the films. Subsequent
action of visible light results in partial recovery of the E-isomer content, whereas annealing leads to the full back conversion. Circular dichroism (CD) measurements revealed formation
of the helical supramolecular structure even in the initial spin-coated polymer films. The E–Z isomerization induces complete disruption of helical order in non-annealed films of the polymer, whereas in the smectic phase
of the annealed film only a significant decrease in CD values was found. In addition, the photoorientation phenomena induced
by polarized light were studied. It was shown that polarized light induces linear dichroism in the films provided by azobenzene
group orientation and the dichroism is stable at room temperature for a prolonged time. These combined chirooptical and photooptical
features of this novel polymer enable one to consider this multifunctional compound as a promising material for photonics
and for optical applications.
Graphical abstract
相似文献
Alexey BobrovskyEmail: |
4.
X-ray diffraction (XRD) data acquisition and processing software measurements on long-spacing binary systems, including adapted
noise reduction algorithms, has been developed. The computation of XRD patterns has been summarized and the origin of the
distinct patterns of long-spacing compounds has been illustrated with the aid of such simulations. This also provided the
possibility to evaluate the retrievable amount of information used for graphical or numerical indexing programs. Numerical
indexing programs were applied and limits of indexing method have been discussed. Differential scanning calorimetry (DSC)
measurements and temperature-dependent XRD measurements have been carried out for the concentrations x
KC
12 = 0.50 and 0.30 of the K-laurate/glycerol system. The analysis of the small- and wide-angle diffractograms in the various
phase regions of the binary system as well as the DSC measurements provided the following results:
– The creation of the lamellar phase extends over a temperature range of ΔT≈ 20 K at a concentration of x
KC
12 = 0.50. The lamellas show a reduced degree of order.
– The crystalline-to-gel phase transition is accompanied by a leap in the d values corresponding to the small-angle reflexes. Also a distinct splitting of the small-angle reflexes is observed within
the gel phase. Simultaneously a rearrangement and intensity decay of the wide-angle reflexes occurs. Since some wide-angle
reflexes are still present, the structure can be considered to have a partially reduced three-dimensional order.
– During the creation of lamellar phases the d value decreases sharply with rising temperature. This decrease of d can be interpreted as a further decay of molecular order in the hydrocarbon chains of the K-laurate within the bilayers.
– The XRD measurements correlate with the DSC data. According to our measurements a revision of the phase diagram with respect
to the actual extension of the gel-phase region was necessary.
Received: 3 March 1999 Accepted in revised form: 29 March 1999 相似文献
5.
Gerhard Kahl Elisabeth Schöll-Paschinger Andreas Lang 《Monatshefte für Chemie / Chemical Monthly》2001,132(11):1413-1432
Summary. Compared to the simple one-component case, the phase behaviour of binary liquid mixtures shows an incredibly rich variety
of phenomena. In this contribution we restrict ourselves to so-called binary symmetric mixtures, i.e. where like-particle interactions are equal (Φ11(r) = Φ22(r)), whereas the interactions between unlike fluid particles differ from those of likes ones (Φ11(r) ≠ Φ12(r)). Using both the simple mean spherical approximation and the more sophisticated self-consistent Ornstein-Zernike approximation, we have calculated the structural and thermodynamic properties of such a system and determine phase diagrams,
paying particular attention to the critical behaviour (critical and tricritical points, critical end points). We then study
the thermodynamic properties of the same binary mixture when it is in thermal equilibrium with a disordered porous matrix
which we have realized by a frozen configuration of equally sized particles. We observe – in qualitative agreement with experiment
– that already a minute matrix density is able to lead to drastic changes in the phase behaviour of the fluid. We systematically
investigate the influence of the external system parameters (due to the matrix properties and the fluid–matrix interactions)
and of the internal system parameters (due to the fluid properties) on the phase diagram.
Received June 27, 2001. Accepted July 2, 2001 相似文献
6.
Gerhard Kahl Elisabeth Sch?ll-Paschinger Andreas Lang 《Monatshefte für Chemie / Chemical Monthly》2001,308(5):1413-1432
Compared to the simple one-component case, the phase behaviour of binary liquid mixtures shows an incredibly rich variety of phenomena. In this contribution we restrict ourselves to so-called binary symmetric mixtures, i.e. where like-particle interactions are equal (Φ11(r) = Φ22(r)), whereas the interactions between unlike fluid particles differ from those of likes ones (Φ11(r) ≠ Φ12(r)). Using both the simple mean spherical approximation and the more sophisticated self-consistent Ornstein-Zernike approximation, we have calculated the structural and thermodynamic properties of such a system and determine phase diagrams, paying particular attention to the critical behaviour (critical and tricritical points, critical end points). We then study the thermodynamic properties of the same binary mixture when it is in thermal equilibrium with a disordered porous matrix which we have realized by a frozen configuration of equally sized particles. We observe – in qualitative agreement with experiment – that already a minute matrix density is able to lead to drastic changes in the phase behaviour of the fluid. We systematically investigate the influence of the external system parameters (due to the matrix properties and the fluid–matrix interactions) and of the internal system parameters (due to the fluid properties) on the phase diagram. 相似文献
7.
Angela Šurca Vuk Boris Orel Goran Dražič Philippe Colomban 《Monatshefte für Chemie / Chemical Monthly》2002,133(6):889-908
Summary. Orthovanadate (M
3+VO4; M = Fe, In) and vanadate (Fe2V4O13) thin films were prepared using sol-gel synthesis and dip coating deposition. Using analytical electron microscopy (AEM),
the chemical composition and the degree of crystallization of the phases present in the thin Fe–V–O films were investigated.
TEM samples were prepared in both orientations: parallel (plan view) and perpendicular (cross section) to the substrate. In
the first stages of crystallization, when the particle sizes were in the nanometer range, the classical identification of
phases using electron diffraction was not possible. Instead of measuring d values, experimentally selected area electron diffraction (SAED) patterns were compared to calculated (simulated) patterns
in order to determine the phase composition. The problems of evaluating the ratio of amorphous and crystalline phases in thin
films are reported.
Results of TEM and XRD as well as IR and Raman spectroscopy showed that the films made at lower temperatures (300°C) consisted of nanograins embedded in the dominating
amorphous phase. Characteristic vibrational spectra allowed to distinguish between the different crystalline phases, since
the IR and Raman bands showed broadening due to the decreasing particle size of the films thermally treated at lower temperatures. Vibrational
analysis also showed that the electrochemical cycling of crystalline films led to spectra that were in close agreement with
the spectra of the nanocrystalline films prepared at lower temperatures. The formation of a nanocrystalline structure is therefore
a prerequisite for obtaining a higher charging/discharging stability of Fe–V–O and In–V–O films.
Received October 4, 2001. Accepted (revised) November 23, 2001 相似文献
8.
I. Khidirov 《Russian Journal of Inorganic Chemistry》2011,56(2):298-303
Full-profile (Rietveld) analysis of neutron diffraction patterns was used to show that the homogeneity ranges of a tetragonal
phase ɛ-Ti2N1 − x
and an ordered tetragonal phase δ′-Ti2N2x
phase of the Ti-N system lie within 0.38 ≤ N/Ti ≤ 0.42 and 0.45 ≤ N/Ti ≤ 0.50, respectively. Unit cell parameters were determined
for ɛ and δ′ phases at the lower and upper boundaries of the homogeneity ranges. A cubic nitride phase having a short-range
order in the nitrogen arrangement was shown to exist in the concentration range 0.45 ≤ N/Ti ≤ 0.75 at relatively high temperatures.
The short range order transforms to a long-range order below 800 K in the concentration range 0.45 ≤ N/Ti ≤ 0.50. Phase transition
features in titanium nitride were determined for the concentration range TiN0.45–TiN0.50. A revised version of a fragment of the Ti-N phase diagram was proposed proceeding from the formation conditions and the
existence ranges of the δ′ and ɛ phases and on the basis of literature data. 相似文献
9.
N. G. Chernorukov A. V. Knyazev E. N. Bulanov 《Russian Journal of Inorganic Chemistry》2010,55(9):1463-1470
Compounds of composition Pb5(P
x
V1−x
O4)3Cl (0 ≤ x ≤ 1), which are synthetic analogues of minerals pyromorphite, vanadinite, and endlichite, were synthesized for the first
time by high-temperature solid-phase reactions. X-ray diffraction and IR spectroscopy were used to determine the structure
of the compounds and revealed complete miscibility in the solid phase of the Pb5(PO4)3Cl-Pb5(VO4)3Cl binary system. Adiabatic reaction calorimetry was used to determine standard enthalpies of mixing and formation and showed
that the regular solutions model is applicable to the Pb5(PO4)3Cl-Pb5(VO4)3Cl system. Differential thermal analysis in tandem with high-temperature X-ray diffraction was used to study the phase diagram
and characterize phase transitions. 相似文献
10.
Alexandru T. Balaban Milan Randić Damir Vukičević 《Journal of mathematical chemistry》2008,43(2):773-779
We report for the trivalent regular and semiregular polyhedra (three Platonic and seven Archimedean carbon polyhedra) the
π-electron partition between rings of various sizes based on considering all their resonance structures. It was found that
small odd-membered (3-and 5-membered) faces are assigned a lower share of π-electrons than that corresponding to equipartition (i.e., 1/3 of an electron for carbon atoms shared between three rings).
In contrast, 4-membered rings obtain a larger share of π-electrons than that corresponding to equipartition. 相似文献
11.
N. A. Santos R. Rosenhaim M. B. Dantas T. C. Bicudo E. H. S. Cavalcanti A. K. Barro I. M. G. Santos A. G. Souza 《Journal of Thermal Analysis and Calorimetry》2011,103(2):501-506
The synthesis of pigments from the system Ce1−x
O2–M
x
O (M = Cu, Co) was achieved via a polymeric precursors method, Pechini method. Differential scanning calorimetry (DSC) and
thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis.
The TG and DSC results revealed a series of decomposition temperatures due to different exothermal events, which were identified
as H2O elimination, organic compounds degradation, and phase formation. X-Ray diffraction patterns show the presence of pure cubic
CeO2 phase for the samples with low Cu and Co loading. A decrease of the specific surface area with increasing copper and cobalt
content was observed. The UV–visible diffuse reflectance technique was employed to study the optical properties in the 200–800 nm
range. Colorimetric coordinates L*, a*, b* were calculated for the pigment powders. The powders presented a variety of colors from yellow for pure CeO2, to brown for the ones loaded with copper and gray for the ones with cobalt. 相似文献
12.
In this work, we first present a detailed analysis of temperature-time duality in the 3D Ising model, by inspecting the resemblance
between the density operator in quantum statistical mechanics and the evolution operator in quantum field theory, with the
mapping β = (k
B
T)−1 → it. We point out that in systems like the 3D Ising model, for the nontrivial topological contributions, the time necessary
for the time averaging must be infinite, being comparable with or even much larger than the time of measurement of the physical
quantity of interest. The time averaging is equivalent to the temperature averaging. The phase transitions in the parametric
plane (β, it) are discussed, and a singularity (a second-order phase transition) is found to occur at the critical time t
c
, corresponding to the critical point β
c
(i.e, T
c
). It is necessary to use the 4-fold integral form for the partition function for the 3D Ising model. The time is needed to
construct the (3 + 1)D framework for the quaternionic sequence of Jordan algebras, in order to employ the Jordan-von Neumann-Wigner
procedure. We then turn to discuss quite briefly temperature-time duality in quantum-chemical many-electron theory. We find
that one can use the known one-dimensional differential equation for the Slater sum S(x, β) to write a corresponding form for the diagonal element of the Feynman propagator, again with the mapping β → it. 相似文献
13.
The K-stearate/glycerol (KC18/Gl) binary system was studied at mole fractions of stearate of x
KC18 = 0.10, 0.25, 0.30 and 0.50. Small- and wide-angle X-ray diffraction (XRD) measurements were combined with differential scanning
calorimetry (DSC) measurements at different temperatures. The investigations were intended to verify the previously published
phase diagram and were targeted at the confirmation of the gel-like (G1) phase and the isotropic (I) phase. The XRD and DSC measurements lead to the conclusion that the G1 phase as well as the I phase, the existence of which had been proposed from texture observations, do in fact not exist. Consequently,
a correction of the preliminary phase diagram is given. This corrected phase diagram reveals the crystalline phase (C) ⇆ gel
phase (G) ⇆ hexagonal phase (Hα) ⇆ isotropic, micellar phase phase transitions for low KC18 concentrations of x
KC18 = 0.15–0.3 and the C ⇆ G ⇆ lamellar phase (Lα) phase transitions for concentrations about or higher than x
KC18 = 0.35. The C, G, Lα and Hα phases have been further characterized by structural parameters (characteristic d values) as a function of temperature. The phase transitions C ⇆ G, G ⇆ Lα and G ⇆ Hα correlate with sharp shifts in the d value of the first small-angle reflections.
Received: 20 April 1999 Accepted: 28 July 1999 相似文献
14.
Dr. Mari Annadhasan Avulu Vinod Kumar Prasenjit Giri Sridatri Nandy Prof. Manas K. Panda Prof. K. V. Jovan Jose Prof. Rajadurai Chandrasekar 《Angewandte Chemie (International ed. in English)》2023,62(25):e202302929
We demonstrate an innovative technique to achieve organic 2D and 3D waveguides with peculiar shapes from an acicular, stimuli-responsive molecular crystal, (2Z,2′Z)-3,3′-(anthracene-9,10-diyl)bis(2-(3,5-bis(trifluoromethyl)phenylacrylonitrile), Ant-CF3. The greenish-yellow fluorescent (FL) Ant-CF3 molecular crystals exhibit laser power-dependent permanent mechanical bending in 2D and 3D. Investigation of a single-crystal using spatially-resolved Raman/FL/electron microscopy, and theoretical calculations revealed photothermal (Z,E)/(E,E) isomerization-assisted transition from crystalline to amorphous phase at the laser-exposed regions. This phenomenon facilitates the dimension engineering of a 1D crystal waveguide into 2D waveguide on a substrate or a 3D waveguide in free space. The bends can be used as interconnection points to couple different optical elements. The presented technique has broader implications in organic photonics and other crystal-related photonic technologies. 相似文献
15.
Ambika Bawa Lokesh K. Gangwar Aastha Dhingra Rajesh Surinder P. Singh 《Liquid crystals》2019,46(2):166-175
The behaviour of dielectric relaxation process has been investigated in four ferroelectric liquid crystal (FLC) materials having different spontaneous polarisation (Ps) values. Ps effect on the permittivity in four different FLCs has been carried out in highly anchored sample cells around ~8 μm thick. It has been found that the main contribution to the dielectric permittivity in chiral Smectic C (SmC*) phase is due to Goldstone mode (GM) and partially unwound helical mode (p-UHM). In higher PS value FLC materials, the p-UHM process is found to dominate the dielectric properties. It has also been observed that p-UHM process is highly dependent on the probing ac voltage and temperature, whereas GM is found to be weakly dependent of probing voltage and temperature in SmC* phase of all the studied FLC materials. The influential contribution of p-UHM has exhibited the dielectric properties in its intrinsic frequency range making the materials suitable for futuristic display and photonics devices. 相似文献
16.
Valérie Bernat Catherine Ringard-Lefebvre Geneviève Le Bas Sylviane Lesieur 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):113-119
Interactions of α-cyclodextrin (α-CD) with dimyristoylphosphatidylcholine (DMPC) and Egg phosphatidylcholine (Egg-PC) were studied (i) by analyzing surface
pressure-area isotherms and surface tension of phospholipid monolayers formed at the interface between air and α-CD aqueous solutions and (ii) by X-ray diffraction performed on fully hydrated α-CD/phospholipid binary mixtures. The cyclodextrin molecules strongly interact with the two-dimension phospholipid assembly.
Their addition into the aqueous sub-phase leads to the removal of part of the phospholipids from the air-water interface:
the higher the α-CD concentration, the higher the phospholipid depletion. This should preferentially involve interactions between cyclodextrin
and the phosphatidylcholine head group as α-CD is water-soluble and not surface-active. At the three-dimension level, the bilayer packing of the phospholipid lamellar
phase appears not affected by the presence of cyclodextrin as shown by X-ray scattering at small angles whereas wide-angle
diffraction patterns reveal the formation of a crystalline phase organized in a pseudo-hexagonal lattice usually characteristic
of α-CD dimers. These results point out that α-CD should interact with bilayer-forming phospholipid molecules but likely according to a process that would preserve intact
at least a part of the multilamellar assembly. 相似文献
17.
Pranesh Muralidhar Elmar Bonaccurso Günter K. Auernhammer Hans-Jürgen Butt 《Colloid and polymer science》2011,289(14):1609-1615
The initial stages of spontaneous spreading of a solvent drop (toluene) on the surface of a soluble polymer (polystyrene)
have been studied with a high-speed camera. For drops of 1–4 μL volume, the increase in contact radius r can be described by a power law r μ ta r \propto {t^{\alpha }} , with the spreading exponent α = 0.50 and for the first ≈8 ms. Thereafter, the three-phase contact line was pinned leading to a macroscopic static contact
angle of Θ0 = 12–15°. The insoluble liquids ethanol (α = 0.47, Θ0 = 0) and water (α = 0.35, Θ0 = 90°) showed a slower spreading. We attribute the fast spreading of toluene to the strong interaction with the polymer,
like in reactive wetting. The finite macroscopic contact angle indicates the formation of a ridge by softening of polystyrene
due to permeated toluene and the subsequent plastic deformation by the surface tension of the liquid. This interpretation
is supported by experiments on polymers grafted from a silicon wafer. Toluene completely wets polymer brush surfaces. Transport
of toluene through the vapor phase plays a significant role. 相似文献
18.
J. Kevelam J. B. F. N. Engberts M. J. Blandamer B. Briggs P. M. Cullis 《Colloid and polymer science》1998,276(2):190-194
Differential scanning microcalorimetric thermograms have been recorded for aqueous solutions containing vesicles formed by
sodium di-n-dodecyl phosphate, in the presence of different concentrations of poly(sodium acrylate-co-n-alkyl methacrylate), where n-alkyl= C9H19, C12H25, C18H37. The mole fraction of hydrophobic moieties in the copolymer is 0.04. The main phase transition temperature (T
m) is hardly affected by the presence of poly(sodium acrylate)s bearing n-dodecyl chains, whereas the anchoring of polymers bearing n-nonyl or n-octadecyl groups reduces the main phase transition temperature significantly from ca. 34 °C to ca. 32 °C. In parallel, the
enthalpy of transition per mole of DDP monomer (Δm
H
int) is lowered upon adding polymer. Again, the polymer containing n-dodecyl moieties hardly affects Δm
H
int. These patterns are explained by the notion that the extent of the disruptive effect of alkyl chains incorporated into the
bilayer depends on the extent of the mismatch between the chain lengths of the intruding alkyl chains and the hydrophobic
moieties composing the vesicle bilayer. Added hydrophobically modified polymers increase the cooperativity of the melting
process, as shown by the increase of n
DDP. We suggest that the anchoring poly(sodium acrylate-co-n-alkyl methacrylate) relieves the strain in the curved outer monolayer of a pure DDP bilayer by allowing the presence of larger
“patches” characterized by low curvature.
Received: 12 May 1997 Accepted: 20 October 1997 相似文献
19.
Ying Hui Shao Xiao Ning Ren Zi Ru Liu Xiang Zhang 《Journal of Thermal Analysis and Calorimetry》2011,103(2):617-623
The eutectic ternary phase diagrams of some typical volatilizable energetic materials have been investigated by high pressure
differential scanning calorimeter (PDSC). The ternary H–X phase diagrams for TNT/TNAZ/DNTF (TTD) and TNAZ/DNTF/RDX (TDR) systems were constructed by the correlation of the apparent
fusion heat with the composition (H–X method). And, the ternary T–X phase diagrams (the temperature dependence on composition) for the two ternary systems were constructed by calculating from
the data of the five T–X binary phase diagrams. The eutectic compositions (mol%) of TTD and TDR ternary systems were obtained to be 52.3/27.3/20.4
(H–X method), 53.2/25.8/21.0 (T–X method) and 54.9/39.6/5.5 (H–X method), 55.1/42.2/2.7 (T–X method), respectively. The eutectic temperatures of the ternary systems were obtained by PDSC determination and T–X method calculation to be 76.5 and 76.7 °C, 47.5 and 50.2 °C, respectively. It is shown that the results obtained by two methods
are in agreement and the error in measuring or calculating eutectic compositions and temperatures for the two ternary systems
are within allowable ranges of ±3 mol% and ±3 °C, respectively. Moreover, by means of constructing two ternary H–X phase diagrams with different fixed composition of a component and comparing the apparent fusion heat of eutectics with calculated
one, the results obtained from H–X method for TTD system were proved. The results showed that the gasification or volatilization of easy volatile materials
could be efficiently restrained by high pressure atmosphere, and the perfectly and ideally H–X ternary phase diagrams can be constructed. In comparison with T–X method, H–X method has as a virtue of being quick and simple, especially on constructing ternary phase diagram. 相似文献
20.
V. V. Kochervinskii S. G. Yudin I. S. Zanaveskina H. A. Arkharova V. V. Klechkovskaya B. V. Lokshin 《Polymer Science Series A》2010,52(1):40-48
The relationship between electrophysical properties of super thin Langmuir-Blodgett films of polyvinylidene fluoride and their
structural parameters via electron-diffraction and IR-spectroscopy methods was studied. According to analysis of the data,
α and γ modifications were formed in addition to the β form. The occurrence of the α and γ species, which were responsible
for the conformations TGTG
− and T
3
GT
3
G
−, was detected both from the absorbance bands and from the respective reflections in the electron-diffraction patterns. In
addition, the electron-diffraction data showed the formation of stratified textures. The polarization-switching curves acquired
at 36°C revealed a low degree of spontaneous polarization within a wide energy distribution of domains, which were characterized
by an average coercive field of 400 MV/m that reflected the change of polymorphous transformations in an electric field. Moreover,
at 49°C, the spontaneous-polarization-switching curves indicated a process with a low coercive field. The observations probably
are related to the higher mobility in the crystals of the α phase that might have eased the spontaneous polarization switching. 相似文献