Journal De Physique Ii最新文献

{"title":"Tack of a polymer melt : Adhesion measurements and fracture profile observations","authors":"T. Ondarçuhu","doi":"10.1051/JP2:1997220","DOIUrl":"https://doi.org/10.1051/JP2:1997220","url":null,"abstract":"We present an experimental study of the tack of a model polymer melt by the probe tack test coupled with an optical observation of the fracture profile. This set-up allowed us to study the different processes involved in tack and to estimate their importance. We distinguished three different regimes that can be correlated to the rheological properties of the adhesive. In particular, the regime where viscoelastic losses in the bulk of the polymer are important is discussed in detail, in the frame of a recent model by de Gennes. We found, in this case, an enhancement of the energy of adhesion and put into evidence peculiar fracture profiles similar to the trumpet profile predicted by the model. We also studied the influences of surface roughness and polymer adsorption on the formation of the bond.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"44 1","pages":"1893-1916"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84572674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inclusions in Thin Smectic Filns","authors":"P. Sens, M. S. Turner","doi":"10.1051/JP2:1997218","DOIUrl":"https://doi.org/10.1051/JP2:1997218","url":null,"abstract":"We study theoretically the behaviour of inclusions in thin films of smectic-A liquid crystal consisting of a stack of regularly spaced membranes. Such membranes are frequently formed in thin diblock copolymer films or in solutions of amphiphilic surfactants. Inclusions, such as colloidal particles or large proteins, couple locally to the smectic and may deform the membranes over a large length scale. Using the Landau-de Gennes description of smectic liquid crystals we obtain the deformation field of the membranes for the two cases of a freely suspended film and a film on a rigid substrate. In the first case we compare and contrast with earlier work on inclusions confined between two membranes and in a lamellar phase of infinite thickness. We show that the existence of an overshoot in the deformation of the layers is intrinsically related to the finite size of the sample. This leads to qualitative differences in the interaction potential between two inclusions for finite and infinite systems. The interaction, monotonically attractive for infinite systems, becomes repulsive at large distance is the sample is finite. We show that the equilibrium position of the particle depends on the surface tension at the film boundary and give quantitative predictions for the particle-induced deformation of the membranes.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"21 1","pages":"1855-1870"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79794378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Superposition States in Cavities Fed by Injected Atoms","authors":"P. Marian, T. A. Marian","doi":"10.1051/JP2:1997106","DOIUrl":"https://doi.org/10.1051/JP2:1997106","url":null,"abstract":"We study the possibility of producing disentangled states in the 3aynes- Cummings model when the input field is a superposition of two Fock states, jM) and jM + I), and the atom is initially in a superposition of its two stationary states. In the case of large M, we show that 3aynes-Cummings interaction provides quantum state swapping between the two qubits (atom and field).","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"8 1","pages":"1753-1760"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90331060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From Semi-Flexible Polymers to Membranes: Anomalous Diffusion and Reptation","authors":"R. Granek","doi":"10.1051/JP2:1997214","DOIUrl":"https://doi.org/10.1051/JP2:1997214","url":null,"abstract":"The dynamics of semi-flexible polymers and membranes is discussed. The effect of thermal undulations on both the transversal and longitudinal Mean Square Displacement (MSD) of a tagged monomer is studied in free polymers and membranes. The two MSDs are found to be proportional to one another, and behave as ∼ t 3/4 for polymers and ∼ t 2/3 for membranes on the short time scale. The longitudinal motion is shown to be linked to the dynamics of fluctuations of the projected length (area) of the polymer (membrane). We demonstrate how, at long times, these fluctuations lead to reptation motion of the polymer (membrane) in the longitudinal direction. We generalize this approach to investigate the motion of a membrane between two plates and a polymer in a tube. The latter problem is used as a model for polymer motion in semi-dilute solutions in which the persistence length is longer than the entanglement length. Such systems are not suitable for the classical reptation model of de-Gennes and of Doi and Edwards, which was designed for chains that are flexible on the entanglement distance. The reptation diffusion coefficient and relaxation times that we obtain have the same scaling with chain length L as in the classical reptation model, but differ greatly in factors that are dependent on the ratio of persistence length to entanglement length. We also discuss the diffusion of a tagged monomer under imposed tension and liquid crystalline order.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"1 1","pages":"1761-1788"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82354037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optical properties and phenomenological theory of ferri-ferri phase transitions in antiferroelectric liquid crystals","authors":"P. Gisse, M. Sidir, V. Lorman, R. Farhi, J. Pavel, H. Nguyen","doi":"10.1051/JP2:1997216","DOIUrl":"https://doi.org/10.1051/JP2:1997216","url":null,"abstract":"Optical rotatory power and Raman scattering experiments on chiral liquid crys- tals belonging to a series which exhibits one or two ferrielectric phases have been performed. The results of these non-perturbative techniques show that, depending upon the aliphatic chain length, a first order transition with a jump in sign and value of the helical pitch, or a divergence and sign reversal of the pitch with no transition can occur in these systems. These observations are in agreement with a generalized Landau-de Gennes phenomenological model predicting that the ferrielectric phases, when both exist, should be isostructural.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"28 1","pages":"1817-1828"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88265518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Small-Angle Scattering Study of the Bulk Structure of a Symmetric Diblock Copolymer System","authors":"C. Papadakis, K. Almdal, K. Mortensen, D. Posselt","doi":"10.1051/JP2:1997217","DOIUrl":"https://doi.org/10.1051/JP2:1997217","url":null,"abstract":"The bulk structure of a homologous series of symmetric polystyrene-polybutadiene (SB) diblock copolymers is investigated using small-angle X-ray and neutron scattering (SANS). The study focuses on the lamellar thickness, the lamellar correlation length and the concentration profile as a function of the chain length and the preparation method applied. The characteristic length, D, scales with the chain length, N, in the whole range studied, but with a clear change in scaling exponent near X N = 29, in accordance with theoretical predictions of a crossover from an Intermediate-Segregation Regime (ISR) to the Strong-Segregation Limit (SSL). In the ISR ( X N≃5 - 29), D is found to scale like D N 0.83 and in the SSL (XN > 29) like D N 0.61 . The temperature dependence of the SANS spectra is studied for a low molar mass sample in an interval around the order-disorder transition temperature (T ODT ). The peak position is found to vary more strongly with temperature than expected for Gaussian chains. Only a weak discontinuity of the peak position at T ODT is observed. In summary, the phase behavior of symmetric SB diblock copolymers in the bulk spans three regimes: the Gaussian regime in the region X N 29.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"57 1","pages":"1829-1854"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82695310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An AC Electrooptic Technique for Measuring the Flexoelectric Coefficient (e1 + e3) and Anchoring Energies of Nematics","authors":"S. R. Warrier, N. V. Madhusudana","doi":"10.1051/JP2:1997215","DOIUrl":"https://doi.org/10.1051/JP2:1997215","url":null,"abstract":"We report an AC technique to measure both the sign and magnitude of (e 1 + e 3 ) using electrooptic measurements on a hybrid aligned nematic cell. A detailed numerical analysis of the optical signal allows us to obtain the temperature dependences of (e 1 + e 3 ), the rotational viscosity coefficient γ 1 as well as the anchoring strengths at the two surfaces. Our measurements on CCH-7 show the following interesting results. a) The extrapolation length L 1 at the homeotropic surface shows a small decrease as the temperature is increased to 66 °C beyond which it shows a sharp increase which we interpret as arising from a softening of the chains of the aligning ODSE layer. b) The slope of the temperature dependence of the extrapolation length L u at the homogeneous surface changes sign around 72 °C. c) (e 1 + e 3 )/S is a constant upto 72 °C and decreases rapidly beyond this temperature. The last two results are attributed to an increase in the conformational freedom between the rings of CCH-7 molecules beyond that temperature.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"41 1","pages":"1789-1803"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85581800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hysteresis and Recovery Length in a Dry Solid Friction Experiment","authors":"J. Crassous, S. Ciliberto, E. Charlaix, C. Laroche","doi":"10.1051/JP2:1997213","DOIUrl":"https://doi.org/10.1051/JP2:1997213","url":null,"abstract":"We report an experiment on dry friction between two elastic surfaces made of millimetric steel spheres embedded in an elastic medium. We study the hysteresis cycle of the tangential force induced by a quasi-static cyclic displacement. At low velocities, hysteresis effects are fully characterized by a recovery length comparable to the size of the steel spheres. This length is independent of the velocity and of the normal load. We propose an interpretation for this recovery length with a simple model of discrete contacts. Dry solid friction occurs in a wide range of systems and is of enormous practical importance. The interest of the physicists in this subject has been renewed recently, due to the development of earth-quake models (1), as well as the analogies with pinning problems such as magnetic vortices, charge density waves, fracture fronts, wetting hysteresis, etc. From a macroscopic point of view solid friction is a phenomenon with a well defined threshold. It is very well known that two solids put in contact with each other remain at rest until the tangential force applied to them reaches a threshold value Fa = psFN, where ps is the static friction coefficient and FN the normal force applied to the bodies. Above this threshold the bodies enter into a relative motion. If the two bodies are moved periodically back and forth on a distance Ax, the existence of the threshold clearly produces a mechanical hysteresis because one needs to change the driving force from Fa to -Fa in order to reverse the motion. Thus the energy Ed, dissipated to do back and forth the relative displacement Ax, is just Ed ~ 2FaAz, independently of the amplitude of Ax. This value of Ed is a consequence of the fact that, in the standard model, there is no relative displacement of the two solids if the tangential force is below threshold. However it has been known for a long time that surfaces undergoing dry solid friction exhibit displacements at the microscopic scale, called micro-slip, before the macroscopic sliding occurs (2,3). Micro-slip is of interest, not only because of its engineering importance in computer modelling of solid friction, but also in relation with the theories of Inechanical friction based on elastic instabilities in a pinning potential (4-6). In these theories,","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"15 1","pages":"1745-1751"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86319741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of matrix molecular weight on a brush : Like surface layer formed by a polymer functionalised at both ends","authors":"F. Kiff, R. Richards, H. Thompson, D. Bucknall, J. Webster","doi":"10.1051/JP2:1997219","DOIUrl":"https://doi.org/10.1051/JP2:1997219","url":null,"abstract":"Deuteropolystyrene has been functionalised at each end by fluorosilane groups, the polymer obtained had a relative molar mass of 98 x 10 3 . Thin films of this polymer mixed with unfunctionalised hydrogenous polystyrene have been prepared and the blends annealed to equilibrium at 413 K. The distribution of the end functionalised deuteropolymer was obtained by neutron reflectometry and a range of molecular weights of the hydrogenous polystyrene matrix has been used. In all cases the deutero polystyrene was preferentially located at the air-polymer interface to an extent which was far greater than that for unfunctionalised deutero polystyrene in the same hydrogenous matrices. From the near surface depth profiles obtained, the surface excess, surface volume fraction and thickness of the end functionalised deuteropolystyrene rich layer have been obtained as a function of the equilibrium concentration of end functionalised deuteropolystyrene. These parameters have been compared with the predictions of scaling theory for brush like layers of polymers attached to a surface. The surface layer thickness and average volume fraction of the surface layer display stretched wet brush behaviour which is not expected for end functionalised polymers on the basis of the molecular weights explored. The possibility that local grafting densities are significantly higher than the average value is discussed. The shape of the near surface depth profile has been fitted using a self consistent field theory using the sticking energy of the fluorosilane groups as the only adjustable parameter. Fits of reasonable quality were obtained and using this sticking energy the surface volume fractions and normalised surface excess parameters have been calculated and compared with those obtained experimentally. Good agreement between surface volume fractions is obtained, but the agreement between normalised surface excess values becomes increasingly worse as the relative molar mass of the hydrogenous matrix increases.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"21 1","pages":"1871-1891"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84839665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rigid Gaussian Chains I: the Scattering Function","authors":"C. Marques, G. Fredrickson","doi":"10.1051/JP2:1997101","DOIUrl":"https://doi.org/10.1051/JP2:1997101","url":null,"abstract":"We study the scattering function of semiflexible polymer chains within the framework of a rigid Gaussian model for polymers first introduced by Harris and Hearst. The tractability of this model allows for a computation of the most relevant physical properties for any value of the chain rigidity. We also explore at the level of the Random Phase Approximation some of the bulk and surface behaviour of semidilute solutions of semiflexible polymers.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"43 1","pages":"1805-1816"},"PeriodicalIF":0.0,"publicationDate":"1997-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88348529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}