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.
{"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}
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.
{"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}
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).
{"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}
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.
讨论了半柔性聚合物和膜的动力学。在自由聚合物和膜中研究了热波动对标记单体横向和纵向均方位移(MSD)的影响。发现这两个msd彼此成正比，并且在短时间尺度上对聚合物表现为~ t 3/4，对膜表现为~ t 2/3。纵向运动显示与聚合物(膜)的投影长度(面积)波动的动力学有关。我们证明，在很长一段时间内，这些波动如何导致聚合物(膜)在纵向上的重复运动。我们推广这种方法来研究膜在两个板之间的运动和管中的聚合物。后一个问题被用作聚合物在半稀溶液中运动的模型，其中持续长度大于纠缠长度。这样的系统不适合de-Gennes和Doi和Edwards的经典重复模型，这些模型是为纠缠距离具有柔性的链设计的。我们得到的重复扩散系数和弛豫时间与经典重复模型的链长L有相同的标度，但依赖于持续长度与纠缠长度之比的因子差异很大。我们还讨论了标签单体在施加张力和液晶秩序下的扩散。
{"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}
P. Gisse, M. Sidir, V. Lorman, R. Farhi, J. Pavel, H. Nguyen
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.
{"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}
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.
{"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}
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.
我们报告了一种交流技术，利用电光测量在混合排列向列电池上测量(e1 + e3)的符号和大小。对光信号的详细数值分析使我们能够获得(e 1 + e 3)的温度依赖性，旋转粘度系数γ 1以及两个表面的锚定强度。我们对CCH-7的测量显示了以下有趣的结果。a)当温度升高到66℃时，各向异性表面外推长度L 1有小幅下降，超过66℃后，外推长度L 1急剧增加，我们认为这是由于排列ODSE层链的软化引起的。b)外推长度L u在均匀表面的温度依赖性斜率在72℃左右变化。c) (e 1 + e 3)/S在72℃前为常数，超过此温度后迅速减小。最后两个结果归因于CCH-7分子环之间构象自由度的增加。
{"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}
J. Crassous, S. Ciliberto, E. Charlaix, C. Laroche
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,
{"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}
F. Kiff, R. Richards, H. Thompson, D. Bucknall, J. Webster
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.
{"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}
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.
{"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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：