共查询到20条相似文献,搜索用时 15 毫秒
1.
Yu Xie Jiankai Tang Zhongyuan Lu Zhaoyan Sun Lijia An 《Journal of Macromolecular Science: Physics》2013,52(9):1183-1197
Poly(ethylene oxide)-poly(propylene oxide)–poly(ethylene oxide) ((EO)n–(PO)m–(EO)n) block copolymers, commercially available as Pluronics (BASF Corp.) and Poloxamers (ICI Corp.), have been widely applied in medicine, biochemistry, and other fields because of their ability to form reversible micelles and physical gels in aqueous solution. Generally, for PEO–PPO–PEO block copolymers with higher ethylene oxide concentration, the micellization and gelation in aqueous solution are easier. However, if we introduce the reverse block copolymer PPO–PEO–PPO into PEO–PPO–PEO aqueous solutions, the micellization and gelation of the system will be more complex. In this work, the reverse block copolymer PO14–EO24–PO14 (17R4) was added to the Pluronics EO20–PO70–EO20 (P123), EO100–PO65–EO100 (F127), and EO133–PO50–EO133 (F108) aqueous solutions with different molar ratios. The rheological properties of different mixtures were measured to study the additive effect on the gelation behavior. The sol–gel transition temperature of the P123, F127, and F108 solutions shifted to a higher temperature when 17R4 was added to the solutions. In addition, the existence of 17R4 greatly affected the stability of gels. These results help to better understand the gelation of Pluronic aqueous solutions. 相似文献
2.
Blends of poly(vinyl chloride) (PVC) and poly(α-methylstyrene-acrylonitrile) (α-MSAN) with variable composition of 0 to 100 wt% were prepared by melt mixing. Properties of binary blends were extensively studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), heat distortion temperature (HDT), mechanical properties, melt flow rate (MFR), and scanning electron microscope (SEM). A single glass transition temperature (Tg ) was observed by DSC and DMTA, indicating miscibility between PVC and α-MSAN. The results of ATR-FTIR indicated that specific strong interactions were not present in the blends and the miscibility was due to interaction between –CN and PVC. With increasing amount of α-MSAN, considerable increase occurred in HDT, flexural strength, and flexural modulus compared with reverse s-shaped decrease in impact strength and elongation at break. Synergism was observed in tensile strength and MFR. No phase separation was observed in SEM photographs, indicating miscibility between PVC and α-MSAN. In addition, morphology of the impact-fractured surfaces, including roughness and non-fused particles, correlated well with the mechanical properties and MFR. 相似文献
3.
Gadzhiev G. M. Gamzatov A. G. Aliev R. A. Abakarova N. S. Emiraslanova L. L. Markelova M. N. Kaul’ A. R. 《Physics of the Solid State》2020,62(5):765-769
Physics of the Solid State - The temperature–frequency spectra of the complex dielectric permittivity of the LuFe2O4 multiferroics have been studied in the temperature range 100–400 K... 相似文献
4.
This paper is devoted to an analysis of the frequency dispersion of dielectric permittivity in order to establish the physical meaning of the dispersion parameters α and β in the Havriliak–Negami model. It is found that parameter α is associated with the spectrum broadening of relaxation time τ. Examples with the appearance of a dispersion with parameter α of about 0.4 and 0.7 are presented. A conclusion is drawn that disorder creates a broadening of the relaxation times. Dispersion parameters α and β are introduced to preserve the unified relaxation time. The possibility of the analysis of experimental results on the basis of the Debye model in order to obtain the relaxation time distribution and determine parameters α and β according to the log(τHN/τ) chart is shown. 相似文献
5.
6.
Physics of the Solid State - At the temperatures T lower than ferroelectric Curie point and various intensities of constant ele-ctric field E=, the dependences of dielectric loss tanδ in the... 相似文献
7.
Mihaela Avadanei 《Journal of Macromolecular Science: Physics》2013,52(3):425-437
Hydrophobic surfaces of poly(ethylene terephtalate) films were modified by using a mild wet chemical procedure with triethylenetetramine as a reagent. The chemical composition was determined by Fourier transform infrared (FTIR) spectroscopy. With the aim of obtaining the depth profile of the newly created species the variable angle attenuated total reflectance (ATR)–FTIR spectroscopy was used. The most important functionalities resulting from the aminolysis that we chose to monitor were amide groups. By varying the incidence angle of the infrared radiation, chemical changes were investigated from layers of different thicknesses. It was observed that the absorption bands attributed to amide moieties became weaker with increasing analyzed depth, with a pronounced heterogeneity near the surface. By assuming an exponential decay for the depth profile spectrally obtained, the surface concentration of amide groups and the decay constant were determined for the reaction times used. 相似文献
8.
Studies on the miscibility and intermolecular specific interactions in the blends of two structurally similar poly(hydroxyether ester)s, poly(hydroxyether terephthalate ester) (PHETE), and poly(hydroxyether benzoate) (PHEB) with poly(4‐vinyl pyrrolidone) (PVPy) are reported. In the miscible blends there are intermolecular specific interactions between PHEEs and PVPy. It was found that intercomponent hydrogen‐bonding interactions in PHETE/PVPy blends are much stronger than those in PHEB/PVPy blends. It seems that the higher ratio of hydroxyl to carbonyl groups results in the stronger intermolecular hydrogen bonding interactions. The difference in intermolecular specific interactions between the two miscible systems is interpreted on the basis of the impact of macromolecular structures on intermolecular specific interactions. The structural characteristics of macromolecular chains, such as chain connectivity, accessibility (or screening effect), and rigidity of the macromolecular chains have a profound effect on the intermolecular interactions. These factors constitute steric hindrance and reduce the specific interactions among functional groups. These factors can become dominant in the blends of polymers. 相似文献
9.
Radiophysics and Quantum Electronics - We present the results of studying variations of the key characteristics of the ionospheric HF channel, namely, the maximum observed (MOF) and the lowest... 相似文献
10.
Di Wu Xun Chen Shenghui Chen Shunxing Lu Fenghua Wang Yumei Zhang 《Journal of Macromolecular Science: Physics》2013,52(3):504-511
Steadyshear and oscillatory shear rheological measurements were performed to characterize the solution rheological behavior of poly(3,3′-diaminodiphenylsulfone terephthaloylchloride) (P(3,3′-DDS-TPC)) in dimethyl sulfoxide (DMSO). The effects of temperature, concentration, and weight-average molar mass () on the rheological properties were investigated. From the temperature dependence of zero-shear viscosity, the flow activation energies, Eη, of P(3,3′-DDS-TPC)/DMSO solutions were calculated. Both the overlap concentration, C*, and the entanglement concentration, Ce, were determined from the concentration dependence of the specific viscosity ηsp. All the P(3,3′-DDS-TPC) solutions, we studied, can be separated into three regimes: the dilute, semidilute-unentangled, and entangled regime with slopes of 1, 1.3, and 3.9, of concentration versus ηsp plots, respectively, which are consistent with scaling predictions for flexible polymers in a good solvent. 相似文献
11.
In this paper,the(2+1)-dimensional Hunter-Saxton equation is proposed and studied.It is shown that the(2+1)-dimensional Hunter–Saxton equation can be transformed to the Calogero–Bogoyavlenskii–Schiff equation by reciprocal transformations.Based on the Lax-pair of the Calogero–Bogoyavlenskii–Schiff equation,a non-isospectral Lax-pair of the(2+1)-dimensional Hunter–Saxton equation is derived.In addition,exact singular solutions with a finite number of corners are obtained.Furthermore,the(2+1)-dimensional μ-Hunter–Saxton equation is presented,and its exact peaked traveling wave solutions are derived. 相似文献
12.
Some authors consider the ψ(4415) to be the 4S or 5S excited tate of a cc pair. Starting from this assumption, we study he decays of the ψ(4415) to DD, D*D*, DSDS, DS*DS*, and get the corresponding branching ratios in terms of the Quark-Pair-Creation (QPC) model. Compared with the experimental data, we find that the results of 4S state agree much better than those of the 5S state. Therefore, it is more reasonable to assume the ψ(4415) to be a 4S state. 相似文献
13.
D. Dudal S. P. Sorella N. Vandersickel 《The European Physical Journal C - Particles and Fields》2010,68(1-2):283-298
In this paper we provide strong evidence that there is no ambiguity in the choice of the horizon function underlying the Gribov–Zwanziger action. We show that there is only one correct possibility which is determined by the requirement of multiplicative renormalizability. As a consequence, this means that relations derived from other horizon functions cannot be given a consistent interpretation in terms of a local and renormalizable quantum field theory. In addition, we also discuss that the Kugo–Ojima functions u(p 2) and w(p 2) can only be defined after renormalization of the underlying Green function(s). 相似文献
14.
The infrared spectra of CH2=CHF have been investigated in the ν5 and ν6 band regions between 1280 and 1400?cm?1, at a resolution of about 0.002?cm?1, using a tunable diode laser spectrometer. These vibrations of symmetry species A′ give rise to a/b-hybrid bands with different contributions from both the components. Spectral analysis resulted in the identification of 1565 (J≤46, K a ≤11) and 1651 (J≤48, K a ≤15) transitions of the ν5 and ν6 fundamentals, respectively. Both bands are perturbed by the nearby states ν8?+?ν9 and ν9?+?ν11 through different Coriolis resonances and an anharmonic interaction. Using Watson's A-reduction Hamiltonian in the Ir representation and perturbation operators almost all the transitions have been fitted simultaneously to a model including six resonances within the tetrad ν5/ν6/ν8?+?ν9/ν9?+?ν11. A set of spectroscopic constants for the ν5 and ν6 bands, as well as parameters for the dark states ν8?+?ν9 and ν9?+?ν11 and coupling constants, have been determined. From spectral simulations the dipole moment ratio |Δμ a /Δμ b | was estimated to be 0.6?±?0.1 and 2.0±0.3 for the ν5 and ν6 bands, respectively. 相似文献
15.
Zhenya Yan 《Czechoslovak Journal of Physics》2003,53(4):297-300
The famous Thomas equation, which arises in the study of chemical exchange processes, is investigated. A more general transformation (called auto-Backlund transformation), which contains the Thomas-Rosales transformation and the Wei-Gao-Zhang transformation, is presented. Based on the general transformation, we may find more information about this equation. Particularly some new exact solutions are found from the special form of the obtained transformation. 相似文献
16.
In this paper, we study the entire radial solutions of the self-dual equations arising from the relativistic SU(3) Chern–Simons model proposed by Kao and Lee (Phys Rev D 50:6626–6632, 1994) and Dunne (Phys Lett B 345:452–457, 1995; Nuclear Phys B 433:333–348, 1995). Understanding the structure of entire radial solutions is one of the fundamental issues for the system of nonlinear equations. In this paper, we prove that any entire radial solutions must be one of topological, non-topological and mixed type solutions, and completely classify the asymptotic behaviors at infinity of these solutions. Even for radial solutions, this classification has remained an open problem for many years. As an application of this classification, we prove that the two components u and v have intersection at most finite times. 相似文献
17.
《Solid State Communications》1987,63(12):1113-1117
The third order optical susceptibilities (χ(3)) of trans- and cis- (CH)x have been determined in the spectral region below the gap by measuring the third harmonic generation efficiency. The magnitude of χ(3) parallel to the polymer chains in trans-(CH)x is in excess of 10−9 esu for wavelengths larger than 1.3 μm, and the spectrum of χ(3) in trans-(CH)x has a sharp two-photon resonance at an energy corresponding to half the semiconducting gap. Both the off resonance and the two-phonon resonance enhanced values of χ(3) are explained by a simple band picture. 相似文献
18.
Monoisotopic stannane 116SnH4 has been investigated at room
temperature in the 600–850 cm-1 and 1270–1600 cm-1 regions by
FTIR spectroscopy with an effective resolution of 2.1 ×10-3 cm-1
and 2.0 ×10-3 cm-1 respectively.
The simultaneous analysis of infrared transitions of both the bending triad
and the hot band {bending triad} minus {bending dyad}, enabled
us to determine 26 parameters for the (22) band and the
combination band (2+4). The standard deviation of the
fit was about 1.5×10-3 cm-1.
In this analysis, we have used, for the bending triad, a Hamiltonian
developed to the fourth order of approximation.
163 observed transitions for the hot band and most observed transitions for
the bending triad spectrum, were assigned to the two bands 22 and (2+4), up to J=9.
In the fit of the Hamiltonian parameters, we have used for the ground state
and for the fundamentals 2 and 4, the parameters
determined by Brunet, Pierre, and Bürger [J. Mol. Spectrosc. 140,
237 (1990)]. 相似文献
19.
In this paper, the Gibbons and Werner technique is used to calculate the weak deflection angle for the black hole solution under the effects of Einstein–Gauss–Bonnet gravity. The Gauss–Bonnet theorem in the limits of weak field is used to evaluate the Gaussian optical curvature in order to obtain the results. The visual effects of the deflection angle on the impact parameter is also looked at and the smallest radius in the non-plasma/plasma medium. Moreover, in order to check the consistency of the results concerning the weak deflection angle, the Keeton and Petters approach is applied to study the deflection angle, which is the expansion of series with a single mass variable, which can be directly addressed by using the post–post Newtonian framework. Furthermore, the deflection angle and shadow under the influence of the plasma is examined by using the motion of particle in a non-magnetized plasma and pressure-free plasma medium as described by the new ray-tracing algorithm. It is shown that plasma as well as Einstein–Gauss-Bonnet gravity corrections are affected by shadows. 相似文献
20.
The relative complex dielectric function, electric modulus and alternating current electrical conductivity spectra and complex impedance plane plots of aqueous solution cast poly(ethylene oxide)–montmorillonite clay (PEO–MMT) nanocomposite films were investigated over the frequency range 20 Hz to 1 MHz at ambient temperature. The intercalated and exfoliated structures of nanoclay dispersed in PEO matrix were recognized by the significant change in real part of dielectric function with clay concentration in the range 0%–20 wt%. The relaxation times corresponding to PEO chain segmental motion and ionic conduction relaxation processes were used to explore the interactions compatibility between PEO molecules and the dispersed MMT clay nanoplatelets and their effect on PEO chain dynamics. Real part of conductivity spectra of these nanocomposites over five decades of frequency has nonlinear behavior, which is influenced by the MMT clay concentration. The complex impedance plane plots confirm the bulk properties of these nanocomposites over the experimental frequency range. 相似文献