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Study of the α-Mechanical Relaxation in Molecular Glass-Forming Liquids 分子玻璃形成液中α-机械弛豫的研究
Pub Date : 1997-11-01 DOI: 10.1051/JP2:1997207
A. Faivre, L. David, J. Pérez
A procedure yielding to the determination of the low-frequency dynamical behavior of glass-forming systems with low glass transition temperature is presented in this paper. The liquids are injected in an inorganic porous medium and the mechanical response of the heterogeneous composite samples is studied. It is shown that the dynamic behavior of the liquid is poorly affected by the presence of the substrate. This enables to build the long-time relaxation diagram for maltitol, sorbitol and LiCl, 6H 2 O. The mechanical measurements are interpreted in the framework of a model based on the assumptions of localized disorder (defects) and hierarchically constrained dynamics in the glass transition region.
本文提出了一种测定低玻璃化转变温度玻璃化体系低频动力学行为的方法。将液体注入无机多孔介质中,研究了非均质复合材料试样的力学响应。结果表明,衬底的存在对液体的动力学行为影响不大。这可以建立麦芽糖醇、山梨醇和LiCl, 6h2o的长期松弛图。力学测量是在基于局部无序(缺陷)和玻璃过渡区分层约束动力学假设的模型框架中解释的。
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引用次数: 8
Modification of the Lamellar Phase in C12E5/Water System by a Random Hydrophilic-Hydrophobic Polyelectrolyte 随机亲疏水聚电解质对C12E5/水体系片层相的改性
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997193
E. Z. Radlinska, T. Gulik‐Krzywicki, F. Lafuma, D. Langevin, W. Urbach, C. Williams
The microstructure of a ternary system of a non-ionic surfactant (n–dodecyl pentaoxyethylene glycol ether, C12E5), water and a water-soluble random heteropolymer, poly (styrene-r-Na styrene sulfonate) with degrees of sulfonation ranging from 30% to 90% is investigated at room temperature. Using small angle X-ray scattering and freeze-fracture electron microscopy we focus on the lamellar phase region and study samples along four different paths of constant surfactant-to-water ratio with increasing polymer content. We demonstrate that for samples with low water content (S/W ratios 3.4 and 4.9), regardless of the sulfonation degree of the polymer, the lamellar phase persists up to several weight percent of polymer and the polymer molecules are confined inside the surfactant bilayers. With increasing quantity of polymer the lamellar phase Bragg peak shifts in a manner consistent with the increase of the lamellar period, which indicates increased bilayer thickness. For mixtures less concentrated in surfactant first order phase transitions are observed for all polymer charge contents when the amount of polymer is increased. For low charge contents of polymer (30% and 45%) the lamellar stack of the polymer-doped surfactant bilayers coexists with either cubic or another lamellar phase and microscopic phase separation is only observed. For large charge contents (65% and 90%) a surfactant-rich lamellar phase coexists with a polymer-rich water solution. It is suggested that the observed phase behaviour is governed by the concentration number of free water molecules.
研究了非离子表面活性剂(正十二烷基五氧基乙二醇醚,C12E5)、水和磺化度为30% ~ 90%的水溶性无规杂聚物(聚苯乙烯-r- na苯乙烯磺酸盐)在室温下三元体系的微观结构。利用小角x射线散射和冷冻断裂电镜技术,我们对层状相区进行了研究,并沿着四种不同的路径研究了表面活性剂与水的比随聚合物含量的增加而不变的样品。研究表明,对于低含水量(S/W比3.4和4.9)的样品,无论聚合物的磺化程度如何,层状相持续存在高达几个重量百分比的聚合物,聚合物分子被限制在表面活性剂双层内。随着聚合物用量的增加,层状相Bragg峰的位移与层状周期的增加一致,表明双层厚度增加。对于表面活性剂浓度较低的混合物,当聚合物用量增加时,观察到所有聚合物电荷含量的一阶相变。当聚合物的电荷含量较低(30%和45%)时,聚合物掺杂表面活性剂双层的片层堆叠与立方相或其他片层相共存,只观察到微观相分离。对于大电荷含量(65%和90%),富含表面活性剂的层状相与富含聚合物的水溶液共存。这表明,所观察到的相行为是由自由水分子的浓度数决定的。
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引用次数: 15
Contact Force Distribution Beneath a Three-Dimensional Granular Pile 三维颗粒桩下的接触力分布
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997200
R. Brockbank, J. M. Huntley, J. M. Huntley, R. Ball
A simple elasto-optical method has been used to measure the normal force distribution under three-dimensional conical piles, for a range of granular materials. The method is based on the measurement of contact diameters of a monolayer of steel balls between the pile and an elastomeric substrate. Experiments on sandpiles confirm the existence of counterintuitive dips in the pressure at the centre of the pile, as reported previously in the literature; the dips were also found in piles of small (ca. 180 pm diameter) glass beads. They were suppressed, however, on increasing the glass bead diameter by a factor of ca. 3. Variations in surface roughness were found to have little effect on the pressure profiles. The probability density function for the normal contact force was approximately negative exponential in form.
本文采用一种简单的弹性光学方法测量了一系列颗粒状材料在三维锥形桩下的法向力分布。该方法基于测量桩与弹性基板之间单层钢球的接触直径。在沙桩上进行的实验证实,正如先前文献中报道的那样,在桩中心存在反直觉的压力下降;在成堆的小玻璃珠(直径约180微米)中也发现了这些浸渍。然而,当玻璃珠直径增加约3倍时,它们被抑制。表面粗糙度的变化对压力分布几乎没有影响。法向接触力的概率密度函数近似为负指数形式。
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引用次数: 101
What about the Backbone Conformation in Nematic and Smectic C Phases of a ``Side-on'' Fixed LCP? A SANS Study “侧对”固定LCP的向列相和密聚C相的主干构象是怎样的?SANS研究
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997194
S. Lecommandoux, L. Noirez, M. Achard, F. Hardouin
Un polymorphisme de type nematique - smectique C a ete pour la premiere fois revele dans les polymeres cristaux liquides en haltere. Des resultats structuraux et conformationnels obtenus par diffusion coherente de neutrons sont presentes pour les deux mesophases. Une inversion de la conformation de la chaine polymere est observee de la phase nematique a la phase smectique C. Ce comportement original est compare au cas de la transition N - S A pour des polymeres cristaux liquides en peigne.
在哑铃液晶聚合物中首次发现了向列-近晶C型多态性。通过相干中子扩散得到的结构和构象结果存在于两个中相中。从向列相到近晶c相,聚合物链的构象发生了逆转。将这种原始行为与梳状液晶聚合物的N - S a转变情况进行了比较。
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引用次数: 10
Kelvin-Helmholtz instability of Langmuir monolayers Langmuir单层膜的Kelvin-Helmholtz不稳定性
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997189
S. Komura, T. Iwayama
We discuss the possibility of Kelvin-Helmholtz instability of a Langmuir monolayer. Even for a positive surface tension, this instability is expected to occur above a critical value of the velocity of the upper air relative to the water. This is in contrast to the buckling transition which occurs for a negative surface tension.
讨论了朗缪尔单分子层存在开尔文-亥姆霍兹不稳定性的可能性。即使表面张力为正,这种不稳定性预计也会发生在高空相对于水的速度的临界值以上。这与负表面张力时发生的屈曲转变形成对比。
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引用次数: 2
Is the electromechanical coupling the driving force for the perpendicular drift of first class cholesteric finger 机电耦合是一级胆甾指垂直漂移的驱动力吗
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997198
L. Gil, S. Thiberge
Dans un cristal liquide cholesterique pris en sandwich entre deux lames de verres conductrices avec des conditions d'ancrage homeotrope, l'apparition de structures spatiales isolees, appelees doigts cholesteriques de premiere espece, est maintenant bien comprise. Quand on soumet le cristal liquide a un champ electrique vertical, on observe alors que ces doigts cholesteriques se mettent a bouger perpendiculairement a son grand axe avec une vitesse V⊥. Dans ce papier, on montre analytiquement que cette vitesse pourrait etre reliee a l'effet Lehmann, et que sa mesure permettrait alors d'estimer la valeur du coefficient de couplage electromecanique.
在具有同素异形体锚定条件的两层导电玻璃夹层的胆碱液晶中,被称为第一种胆碱手指的孤立空间结构的出现现在已经很好地理解了。当液晶受到一个垂直电场时,可以观察到这些胆碱手指开始垂直于它的长轴运动,速度为V⊥。在这篇论文中,分析表明这个速度可能与莱曼效应有关,它的测量将允许估计机电耦合系数的值。
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引用次数: 8
Modification of the Crystallization Kinetics of a Mixed Bath of Alkanes in the Presence of Coil-Crystalline Block Copolymer Micelles 盘状嵌段共聚物胶束存在下烷烃混合浴结晶动力学的改变
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997192
D. Buzza, T. McLeish
Recent Neutron Scattering experiments by Richter et al. [1] show that the presence of coil-crystalline block copolymer (PE-PEP) micelles in a mixed alkane bath suppresses the crystallization out of solution of the long alkane component at low temperatures. Motivated by these experiments, we study theoretically the thermodynamics and kinetics of lamellar coil-crystalline block copolymer micelles in a bimodal solvent to better understand the factors determining the anti-precipitation action of coil-crystalline block copolymers. We assume an Alexander-de Gennes brush model for the strongly stretched corona chains and explicitly account for the polydispersity of the solvent chains. For the thermodynamic distribution of solvent chains in the corona, we find a predominance of short solvent chains to long solvent chains in the corona phase compared to the solvent bath, both with and without nematic interactions in the corona phase. We also calculate the rate of crystallization of the long solvent chains onto the micellar crystal core and find that the rate is sensitive to both brush and core parameters. In particular, we predict that to maximize the rate, both E fold /kTN A and X n need to be made as small as possible, where E fold is the folding energy of the crystal core chains, N A the number of statistical segments of the solvated corona chains and X n parameterises the strength of nematic interactions in the micellar corona. This leads to the surprising result that for fixed E fold , the rate of crystallization is increased when we increase the molecular weight of the corona blocks.
最近Richter等人[1]进行的中子散射实验表明,在混合烷烃浴中,线圈结晶嵌段共聚物(PE-PEP)胶束的存在抑制了长烷烃组分在低温下的结晶出液。在这些实验的激励下,我们从理论上研究了双峰溶剂中层状盘状-结晶嵌段共聚物胶束的热力学和动力学,以更好地了解盘状-结晶嵌段共聚物抗沉淀作用的决定因素。我们假设了强拉伸电晕链的亚历山大-德热纳电刷模型,并明确地解释了溶剂链的多分散性。对于溶剂链在电晕中的热力学分布,我们发现与溶剂浴相比,在电晕相中存在或不存在向列相互作用的情况下,短溶剂链比长溶剂链更占优势。我们还计算了长溶剂链在胶束晶体核心上的结晶速率,发现该速率对电刷和核心参数都很敏感。特别是,我们预测,为了使速率最大化,E fold /kTN A和X n都需要尽可能小,其中E fold是晶体核心链的折叠能量,n A是溶剂化电晕链的统计段数,X n是胶束电晕中向列相互作用强度的参数。这导致了一个令人惊讶的结果,即对于固定的E折叠,当我们增加电晕块的分子量时,结晶速率会增加。
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引用次数: 3
A Single Director Switching Mode for Monodomain Liquid Crystal Elastomers 单畴液晶弹性体的单导开关模式
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997190
P. M. Roberts, G. Mitchell, F. Davis
We report rotation of a single director in a nematic monodomain, acrylate based side-chain elastomer which was subjected to mechanical fields applied at angles in the range 80° 90° to the director, no, present at the time of network formation. Time and spatially resolving wide angle X-ray scattering, together with polarised light microscopy measurements revealed a pronounced, almost discontinuous switching mode at a critical extension as the strain was applied at angles approaching 90° to no, whereas a more continuous rotation was seen when the strain was applied at more acute angles. This director reorientation was more or less uniform across the complete sample and was accompaniecl by a modest decrease in orientation parameter (P2). At strains sufficient to induce switching there was some continuous distribution of director orientations with fluctuations of +10° although there was no evidence for any localised director inhomogenities such as domain formation. The observed deformation behaviour of these acrylate-based nematic monodomains was in accord with the predictions of a theory developed by Bladon et al., in that the complete set of data could be accounted for through a single parameter describing the chain anisotropy. The experimentally deduced chain anisotropy parameter was in broad agreement with that obtained from small-angle neutron scattering procedures, but was somewhat greater than that obtained by spontaneous shape changes at the nematic-isotropic transition.
我们报道了向列单畴中单个定向器的旋转,丙烯酸酯基侧链弹性体受到机械场的作用,与定向器的角度在80°90°范围内,不,在网络形成时存在。时间和空间分辨广角x射线散射,以及偏光显微镜测量显示,当应变以接近90°的角度施加时,在临界扩展处出现了明显的几乎不连续的切换模式,而当应变以更锐角施加时,可以看到更连续的旋转。这种定向器的重新定向在整个样品中或多或少是均匀的,并且伴随着定向参数的适度减少(P2)。在足以诱导转换的应变下,虽然没有证据表明存在任何局部定向物不均匀性,如畴形成,但定向物取向有+10°波动的连续分布。观察到的这些基于丙烯酸酯的向列单畴的变形行为与Bladon等人开发的理论的预测一致,因为完整的数据集可以通过描述链各向异性的单个参数来解释。实验推导出的链各向异性参数与小角中子散射过程得到的参数基本一致,但略大于向列-各向同性跃迁过程中自发形状变化得到的参数。
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引用次数: 19
Surface Effects on Block Copolymer Melts Above the Order-Disorder Transition: Linear Theory of Equilibrium Properties and the Kinetics of Surface-Induced Ordering 嵌段共聚物熔体在有序-无序过渡之上的表面效应:平衡性质的线性理论和表面诱导有序的动力学
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997191
K. Binder, Harry L. Risch, S. Stepanow
A phenomenological theory is developed for static and dynamic aspects ofsurface- induced ordering of symmetrical block copolymers taking fluctuation corrections into account, but, considering conditions where the bulk block copolymer melt is still disordered, and a lin- earized version of the resulting Ginzburg-Landau type equation suffices. Both the semi-infinite geometry and symmetrical films of thickness 2L are treated, applying the same boundary con- ditions as used previously for a treatment of wetting in polymer blends, assuming short range surface forces and a long Wavelength approximation. For the static order parameter profile in thin film geometry, We derive an oscillatory convergence of both amplitude and phase to the corre- sponding properties of the semi-infinite systems, because terms of order exp(-2L/f+) cos(2Lq*) enter, f+ being the correlation length and = 21r/q* the Wave~length of lamellar ordering. It is shown that the conservation of the number of monomers of the two species, Which can be expressed as a global constraint on the order parameter, leads to a non-linear equation for the phase expressed in terms of the amplitude, When one considers the kinetics of ordering. Both numerical and approximate analytical treatments are given to describe the evolution of the considered systems towards equilibrium.
在考虑波动修正的情况下,为对称嵌段共聚物表面诱导有序的静态和动态方面发展了一种现象学理论,但是,考虑到大块嵌段共聚物熔体仍然无序的条件,并且由此产生的金兹堡-朗道型方程的线性化版本就足够了。在处理厚度为2L的半无限几何和对称薄膜时,采用与先前用于处理聚合物共混物润湿相同的边界条件,假设短距离表面力和长波长近似。对于薄膜几何中的静态序参量分布,由于阶项exp(- 2l /f+) cos(2Lq*)进入,其中f+为相关长度,= 21r/q*为层状有序的波长度,我们推导出振幅和相位对半无限系统相应性质的振荡收敛。结果表明,当考虑有序化动力学时,两种单体数量的守恒性(可表示为对有序参数的全局约束)导致以振幅表示的相的非线性方程。给出了数值和近似解析处理来描述所考虑的系统向平衡的演化。
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引用次数: 11
Standing Wave Localized Squares in Pattern-Forming Nonequilibrium Systems 非平衡系统中的驻波定域方阵
Pub Date : 1997-10-01 DOI: 10.1051/JP2:1997188
H. Sakaguchi, H. Brand
Stable standing wave localized solutions of square symmetry are possible for a quintic Swift-Hohenberg type equation with complex coefficients. We point out that these localized solutions, which are surrounded by a pattern-free state exist for a range of values for the external stress parameter subcritically. We discuss similarities to recent experimental observations of standing wave localized squares in granular materials
具有复系数的五次Swift-Hohenberg型方程的稳定驻波局域解是可能的。我们指出,这些被无模式状态包围的局部解存在于外部应力参数的亚临界值范围内。我们讨论了在颗粒材料中的驻波局域方阵的相似之处
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引用次数: 3
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