Nous avons decouvert un systeme mixte constitue d'une phase smectique de membranes fluides (melange en proportion appropriee d'hexanol et de chlorure de cethylpyridinium), dans une solution aqueuse d'un polymere hydrosoluble neutre non adsorbant de tres grande masse moleculaire : le polyvinylpyrolidonne. Ce systeme permet de realiser experimentalement les diverses situations de confinement d'une solution de macromolecules entre deux plans. La presence du polymere entre les membranes induit une interaction effective entre membranes qui depend du regime de confinement. Nous calculons la contribution a la compressibilite smectique de cette interaction effective dans chacun des quatres regimes attendus ; c'est une fonction non monotone de la concentration en polymere dans le solvant. Cette grandeur thermodynamique est particulierement interessante car elle est mesurable par diffusion de rayonnement aux petits angles (X ou neutrons). Notre modele permet d'interpreter quantitativement la separation de phase lamellaire/lamellaire observee par addition progressive de sel pour une composition particuliere du systeme.
{"title":"Smectic Compressibility of Polymer-Containing Lyotropic Lamellar Phases: An Experimental Tool to Study the Thermodynamics of Polymer Confinement","authors":"C. Ligoure, G. Bouglet, G. Porte, O. Diat","doi":"10.1051/JP2:1997139","DOIUrl":"https://doi.org/10.1051/JP2:1997139","url":null,"abstract":"Nous avons decouvert un systeme mixte constitue d'une phase smectique de membranes fluides (melange en proportion appropriee d'hexanol et de chlorure de cethylpyridinium), dans une solution aqueuse d'un polymere hydrosoluble neutre non adsorbant de tres grande masse moleculaire : le polyvinylpyrolidonne. Ce systeme permet de realiser experimentalement les diverses situations de confinement d'une solution de macromolecules entre deux plans. La presence du polymere entre les membranes induit une interaction effective entre membranes qui depend du regime de confinement. Nous calculons la contribution a la compressibilite smectique de cette interaction effective dans chacun des quatres regimes attendus ; c'est une fonction non monotone de la concentration en polymere dans le solvant. Cette grandeur thermodynamique est particulierement interessante car elle est mesurable par diffusion de rayonnement aux petits angles (X ou neutrons). Notre modele permet d'interpreter quantitativement la separation de phase lamellaire/lamellaire observee par addition progressive de sel pour une composition particuliere du systeme.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"55 1","pages":"473-491"},"PeriodicalIF":0.0,"publicationDate":"1997-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91332805","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 present a calculation of the smectic compression modulus B of a lyotropic lamellar phase stabilized by electrostatic interactions. This calculation, based on a numerical solution of the Poisson-Boltzmann equation, shows that the classical analytical expressions of B given in the literature in the two asymptotic limits (absence of added salt, or large added salt concentration) are valid under very restrictive conditions only. The motivation of this study lies in the understanding of the physical behavior of a doped amphiphilic lamellar phase formed from a mixture of non ionic surfactants (Triton X100/Triton X35), cationic surfactant (cetylpyridinium chloride), water, decane and water-soluble polymer (polyvynilpyrolidone). A critical lamellar/lamellar phase separation observed in our system is quantitatively well-explained by using both the present calculations and a recent model proposed by Ligoure et al. which predicts the polymer-mediated intermembrane interaction contribution to the smectic compression modulus.
{"title":"Layer compression modulus of electrostatically stabilized lyotropic lamellar phases revisited : Application to the quantitative analysis of a polymer induced critical SmA-SmA phase separation","authors":"L. Porcar, C. Ligoure, J. Marignan","doi":"10.1051/JP2:1997140","DOIUrl":"https://doi.org/10.1051/JP2:1997140","url":null,"abstract":"We present a calculation of the smectic compression modulus B of a lyotropic lamellar phase stabilized by electrostatic interactions. This calculation, based on a numerical solution of the Poisson-Boltzmann equation, shows that the classical analytical expressions of B given in the literature in the two asymptotic limits (absence of added salt, or large added salt concentration) are valid under very restrictive conditions only. The motivation of this study lies in the understanding of the physical behavior of a doped amphiphilic lamellar phase formed from a mixture of non ionic surfactants (Triton X100/Triton X35), cationic surfactant (cetylpyridinium chloride), water, decane and water-soluble polymer (polyvynilpyrolidone). A critical lamellar/lamellar phase separation observed in our system is quantitatively well-explained by using both the present calculations and a recent model proposed by Ligoure et al. which predicts the polymer-mediated intermembrane interaction contribution to the smectic compression modulus.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"35 1","pages":"493-501"},"PeriodicalIF":0.0,"publicationDate":"1997-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88511138","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 briefly review and re-interpret recent experimental results on shear-induced inhomogeneous flows in complex fluids. These are usually explained in terms of a mechanical instability of the non-linear flow regime. However, in at least two respects, the robustness of the two-state banded-flow regime and the kinetics of band formation under shear, they present striking analogies with ordinary field-induced phase transitions in equilibrium systems. We propose a phenomenological explanation of these effects in terms of an effective non-equilibrium potential that accounts for the free energy stored in a viscoelastic material under steady-shear conditions. Within this picture, a shear-thinning non-homogeneous flow can be shown to be a manifestation of some underlying hidden structural transition.
{"title":"Inhomogeneous Flows of Complex Fluids: Mechanical Instability Versus Non-Equilibrium Phase Transition","authors":"G. Porte, J. Berret, J. Harden","doi":"10.1051/JP2:1997138","DOIUrl":"https://doi.org/10.1051/JP2:1997138","url":null,"abstract":"We briefly review and re-interpret recent experimental results on shear-induced inhomogeneous flows in complex fluids. These are usually explained in terms of a mechanical instability of the non-linear flow regime. However, in at least two respects, the robustness of the two-state banded-flow regime and the kinetics of band formation under shear, they present striking analogies with ordinary field-induced phase transitions in equilibrium systems. We propose a phenomenological explanation of these effects in terms of an effective non-equilibrium potential that accounts for the free energy stored in a viscoelastic material under steady-shear conditions. Within this picture, a shear-thinning non-homogeneous flow can be shown to be a manifestation of some underlying hidden structural transition.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"28 1","pages":"459-472"},"PeriodicalIF":0.0,"publicationDate":"1997-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75525045","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 shear-induced reorientation of the hexagonal surfactant mesophase is investigated by deuterium nuclear magnetic resonance spectroscopy. The NMR spectra of the sheared samples, measured in situ with two different shear geometries, either cone and plate or coaxial cylinders, prove that the hexagonal axis (the director) aligns parallel to the flow. Shear experiments starting from a monodomain sample, with the director initially aligned along the velocity gradient, exhibit an increasing tilt of the director as the shear strain γ grows. The tilt angle is given by arctan γ. This makes evident that the hexagonal lyomesophase behaves like a solid. The analysis of nuclear magnetic resonance spectra and textures observed by polarizing microscopy shows an undulation of the columns in both the quiescent and the sheared state. The amplitude of the undulations decreases with increasing shear strain.
{"title":"Solid-Like Director Reorientation in Sheared Hexagonal Lyotropic Liquid Crystals as Studied by Nuclear Maginetic Resonance","authors":"S. Müller, P. Fischer, C. Schmidt","doi":"10.1051/JP2:1997135","DOIUrl":"https://doi.org/10.1051/JP2:1997135","url":null,"abstract":"The shear-induced reorientation of the hexagonal surfactant mesophase is investigated by deuterium nuclear magnetic resonance spectroscopy. The NMR spectra of the sheared samples, measured in situ with two different shear geometries, either cone and plate or coaxial cylinders, prove that the hexagonal axis (the director) aligns parallel to the flow. Shear experiments starting from a monodomain sample, with the director initially aligned along the velocity gradient, exhibit an increasing tilt of the director as the shear strain γ grows. The tilt angle is given by arctan γ. This makes evident that the hexagonal lyomesophase behaves like a solid. The analysis of nuclear magnetic resonance spectra and textures observed by polarizing microscopy shows an undulation of the columns in both the quiescent and the sheared state. The amplitude of the undulations decreases with increasing shear strain.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":" 32","pages":"421-432"},"PeriodicalIF":0.0,"publicationDate":"1997-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91415424","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}
A. Moskalenko, Yu. A. Kuznetsov, Kenneth A. Dawson
We study the phase transitions of a random copolymer chain with quenched disorder. We calculate the average over the quenched disorder in replica space and apply a Gaussian variational approach based on a generic quadratic trial Hamiltonian in terms of the correlation functions of monomer Fourier coordinates. This has the advantage that it allows us to incorporate fluctuations of the density, determined self-consistently, and to study collapse, phase separation transitions and the onset of the freezing transition within the same mean field theory. The effective free energy of the system is derived analytically and analyzed numerically in the one-step Parisi scheme. Such quantities as the radius of gyration, end-to-end distance or the average value of the overlap between different replicas are treated as observables and evaluated by introducing appropriate external fields to the Hamiltonian. As a result we obtain the phase diagram in terms of model parameters, scaling for the freezing transition and the dependence of correlation functions on the chain index.
{"title":"Random Copolymer: Gaussian Variational Approach","authors":"A. Moskalenko, Yu. A. Kuznetsov, Kenneth A. Dawson","doi":"10.1051/jp2:1997134","DOIUrl":"https://doi.org/10.1051/jp2:1997134","url":null,"abstract":"We study the phase transitions of a random copolymer chain with quenched disorder. We calculate the average over the quenched disorder in replica space and apply a Gaussian variational approach based on a generic quadratic trial Hamiltonian in terms of the correlation functions of monomer Fourier coordinates. This has the advantage that it allows us to incorporate fluctuations of the density, determined self-consistently, and to study collapse, phase separation transitions and the onset of the freezing transition within the same mean field theory. The effective free energy of the system is derived analytically and analyzed numerically in the one-step Parisi scheme. Such quantities as the radius of gyration, end-to-end distance or the average value of the overlap between different replicas are treated as observables and evaluated by introducing appropriate external fields to the Hamiltonian. As a result we obtain the phase diagram in terms of model parameters, scaling for the freezing transition and the dependence of correlation functions on the chain index.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"203 1","pages":"409-419"},"PeriodicalIF":0.0,"publicationDate":"1997-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76200130","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}
S. Buldyrev, L. A. Amaral, L. A. Amaral, S. Havlin, S. Havlin, H. Leschhorn, P. Maass, M. Salinger, H. Stanley, M. H. Stanley
In the preceding paper we presented empirical results describing the growth of publicly-traded United States manufacturing firms within the years 1974--1993. Our results suggest that the data can be described by a scaling approach. Here, we propose models that may lead to some insight into these phenomena. First, we study a model in which the growth rate of a company is affected by a tendency to retain an ``optimal'' size. That model leads to an exponential distribution of the logarithm of the growth rate in agreement with the empirical results. Then, we study a hierarchical tree-like model of a company that enables us to relate the two parameters of the model to the exponent $beta$, which describes the dependence of the standard deviation of the distribution of growth rates on size. We find that $beta = -ln Pi / ln z$, where $z$ defines the mean branching ratio of the hierarchical tree and $Pi$ is the probability that the lower levels follow the policy of higher levels in the hierarchy. We also study the distribution of growth rates of this hierarchical model. We find that the distribution is consistent with the exponential form found empirically.
在前一篇论文中，我们提出了描述1974- 1993年间美国上市制造业公司增长的实证结果。我们的结果表明，数据可以用标度方法来描述。在这里，我们提出的模型可能会导致对这些现象的一些见解。首先，我们研究了一个模型，在这个模型中，公司的增长率受到保持“最优”规模的趋势的影响。该模型得出增长率的对数呈指数分布，与实证结果一致。然后，我们研究了一个公司的分层树状模型，使我们能够将模型的两个参数与指数$beta$联系起来，该指数描述了增长率分布的标准差对规模的依赖。我们发现$beta = -ln Pi / ln z$，其中$z$定义了层次树的平均分支比，$Pi$是层次树中较低层次遵循较高层次策略的概率。本文还研究了该分层模型的增长率分布。我们发现分布与经验发现的指数形式是一致的。
{"title":"Scaling behavior in economics: II. Modeling of company growth","authors":"S. Buldyrev, L. A. Amaral, L. A. Amaral, S. Havlin, S. Havlin, H. Leschhorn, P. Maass, M. Salinger, H. Stanley, M. H. Stanley","doi":"10.1051/jp1:1997181","DOIUrl":"https://doi.org/10.1051/jp1:1997181","url":null,"abstract":"In the preceding paper we presented empirical results describing the growth of publicly-traded United States manufacturing firms within the years 1974--1993. Our results suggest that the data can be described by a scaling approach. Here, we propose models that may lead to some insight into these phenomena. First, we study a model in which the growth rate of a company is affected by a tendency to retain an ``optimal'' size. That model leads to an exponential distribution of the logarithm of the growth rate in agreement with the empirical results. Then, we study a hierarchical tree-like model of a company that enables us to relate the two parameters of the model to the exponent $beta$, which describes the dependence of the standard deviation of the distribution of growth rates on size. We find that $beta = -ln Pi / ln z$, where $z$ defines the mean branching ratio of the hierarchical tree and $Pi$ is the probability that the lower levels follow the policy of higher levels in the hierarchy. We also study the distribution of growth rates of this hierarchical model. We find that the distribution is consistent with the exponential form found empirically.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"9 1","pages":"635-650"},"PeriodicalIF":0.0,"publicationDate":"1997-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74488895","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 compute phase diagrams for diblock copolymers in the mean-field weak- segregation regime as a function of the fraction f of A-monomers and the repulsive interaction XN. We include the ordered bicontinuous double-diamond (OBDD) phase (space group Pn3m) and the gyroid phase (space group Ia3d) as well as lamellae, hexagonal cylinders, and BCC spheres. We find a stable region of gyroid phase between cylinders and larnellae just above the mean-field critical point, in agreement with numerical mean-field calculations. The stability of gyroid depends on the presence of the next higher (220) reflections in addition to the (211) fundamental. The gyroid free energy is favored by terms of the form ~(~~~j ~bj220j and ~b(~i~j~bj220j; the analogous terms are not permitted for OBDD.
{"title":"Analytical Weak-Segregation Theory of Bicontinuous Phases in Diblock Copolymers","authors":"S. Milner, P. Olmsted","doi":"10.1051/JP2:1997122","DOIUrl":"https://doi.org/10.1051/JP2:1997122","url":null,"abstract":"We compute phase diagrams for diblock copolymers in the mean-field weak- segregation regime as a function of the fraction f of A-monomers and the repulsive interaction XN. We include the ordered bicontinuous double-diamond (OBDD) phase (space group Pn3m) and the gyroid phase (space group Ia3d) as well as lamellae, hexagonal cylinders, and BCC spheres. We find a stable region of gyroid phase between cylinders and larnellae just above the mean-field critical point, in agreement with numerical mean-field calculations. The stability of gyroid depends on the presence of the next higher (220) reflections in addition to the (211) fundamental. The gyroid free energy is favored by terms of the form ~(~~~j ~bj220j and ~b(~i~j~bj220j; the analogous terms are not permitted for OBDD.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"1 1","pages":"249-255"},"PeriodicalIF":0.0,"publicationDate":"1997-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80828243","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 consider harmonically undulating ionic surfactant membranes, calculating a general expression for the bending modulus valid for all salt and surfactant concentrations, and surface charge densities. This is achieved through a perturbative expansion of the mean-field electrostatic potential and free energy about a planar reference state, consisting of two parallel planar membranes with intervening salt solution. For a given choice of undulation mode, the result for the bending modulus is seen to be generally the same as that obtained from considerations of membranes deformed into a cylindrical geometry. Thus, we show that the bending modulus is independent of global aggregate geometry, at a general system composition. Specializing to the limit of excess added salt (equivalent to a single undulating membrane in contact with bulk electrolyte), we are able to extend the free energy calculation to fourth order in undulation amplitude, and derive the bending constants of the curvature expansion to this order. These have been suggested previously to be of importance in explaining the stability of bicontinuous crystalline and disordered phases, and the formation of passages in lamellar phases. We also discuss the breakdown of the curvature description at shorter wavelengths.
{"title":"Undulating Charged Fluid Membranes and their Bending Constants","authors":"A. Fogden, J. Daicic, A. Kidane","doi":"10.1051/JP2:1997121","DOIUrl":"https://doi.org/10.1051/JP2:1997121","url":null,"abstract":"We consider harmonically undulating ionic surfactant membranes, calculating a general expression for the bending modulus valid for all salt and surfactant concentrations, and surface charge densities. This is achieved through a perturbative expansion of the mean-field electrostatic potential and free energy about a planar reference state, consisting of two parallel planar membranes with intervening salt solution. For a given choice of undulation mode, the result for the bending modulus is seen to be generally the same as that obtained from considerations of membranes deformed into a cylindrical geometry. Thus, we show that the bending modulus is independent of global aggregate geometry, at a general system composition. Specializing to the limit of excess added salt (equivalent to a single undulating membrane in contact with bulk electrolyte), we are able to extend the free energy calculation to fourth order in undulation amplitude, and derive the bending constants of the curvature expansion to this order. These have been suggested previously to be of importance in explaining the stability of bicontinuous crystalline and disordered phases, and the formation of passages in lamellar phases. We also discuss the breakdown of the curvature description at shorter wavelengths.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"11 1","pages":"229-248"},"PeriodicalIF":0.0,"publicationDate":"1997-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83528201","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}
Deuterium NMR quadrupolar splittings and 2 H - 2 H dipolar couplings observed from perdeuterated 1,6-dimethoxyhexane (CD 3 O(CD 2 ) 6 OCD 3 ) dissolved in a liquid crystal 4'-methoxybenzylidene-4-η-butylaniline (MBBA) were analyzed using the single-ordering-matrix (SOM) and the Photinos-Samulski-Toriumi (P-S-T) models. Within the framework of the rotational isomeric state approximation, intramolecular interactions up to the third-order (between atoms and groups separated by five bonds) were considered. The geometrical parameters and intramolecular interaction energies determined from ab initio molecular orbital calculations were employed. The two simulation models yielded fair agreement between theory and experiment, but were found to give quite different images of the solute chain: (the SOM model), the solute becomes rigid and extended to conform itself to the nematic field; (the P-S-T model), the solute has almost the same degree of flexibility as in the free state, but populations of the anisotropic conformers are selectively enhanced. To reveal the true conformational characteristics of chain molecules in nematic fields, experimental techniques to enable direct and quantitative measurements of the bond conformations are necessary.
{"title":"Conformational and Orientational Characteristics of Chain Molecules Placed in Nematic Fields. Part II","authors":"Yuji Sasanuma","doi":"10.1051/JP2:1997127","DOIUrl":"https://doi.org/10.1051/JP2:1997127","url":null,"abstract":"Deuterium NMR quadrupolar splittings and 2 H - 2 H dipolar couplings observed from perdeuterated 1,6-dimethoxyhexane (CD 3 O(CD 2 ) 6 OCD 3 ) dissolved in a liquid crystal 4'-methoxybenzylidene-4-η-butylaniline (MBBA) were analyzed using the single-ordering-matrix (SOM) and the Photinos-Samulski-Toriumi (P-S-T) models. Within the framework of the rotational isomeric state approximation, intramolecular interactions up to the third-order (between atoms and groups separated by five bonds) were considered. The geometrical parameters and intramolecular interaction energies determined from ab initio molecular orbital calculations were employed. The two simulation models yielded fair agreement between theory and experiment, but were found to give quite different images of the solute chain: (the SOM model), the solute becomes rigid and extended to conform itself to the nematic field; (the P-S-T model), the solute has almost the same degree of flexibility as in the free state, but populations of the anisotropic conformers are selectively enhanced. To reveal the true conformational characteristics of chain molecules in nematic fields, experimental techniques to enable direct and quantitative measurements of the bond conformations are necessary.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"21 1 1","pages":"305-317"},"PeriodicalIF":0.0,"publicationDate":"1997-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86129479","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}
Erica Pelletier, G. F. Belder, G. Hadziioannou, A. Subbotin
We investigate the mechanical properties of ultra-thin layers of polystyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate asa rheometer at the molecular level. Two systems are studied: ''brush/wall'' and ''brush/brush''. A comparison of the normal force curves shows that when brushes are compressed against each other, they contract rather than interpenetrate. Nanorheological experiments have been carried out on both systems but reliable measurements have been obtained only on the brush/wall system. The complex shear modulus, characterizing the confined medium, has been measured as a function of separation. Its distance dependence is compared with a scaling model describing the linear shear behaviour of a brush confined by a neutral surface.
{"title":"Nanorheology of adsorbed diblock copolymer layers","authors":"Erica Pelletier, G. F. Belder, G. Hadziioannou, A. Subbotin","doi":"10.1051/JP2:1997124","DOIUrl":"https://doi.org/10.1051/JP2:1997124","url":null,"abstract":"We investigate the mechanical properties of ultra-thin layers of polystyrene/poly (2-vinylpyridine) (PS/P2VP) block copolymers by means of a Surface Forces Apparatus adapted to operate asa rheometer at the molecular level. Two systems are studied: ''brush/wall'' and ''brush/brush''. A comparison of the normal force curves shows that when brushes are compressed against each other, they contract rather than interpenetrate. Nanorheological experiments have been carried out on both systems but reliable measurements have been obtained only on the brush/wall system. The complex shear modulus, characterizing the confined medium, has been measured as a function of separation. Its distance dependence is compared with a scaling model describing the linear shear behaviour of a brush confined by a neutral surface.","PeriodicalId":14774,"journal":{"name":"Journal De Physique Ii","volume":"26 1","pages":"271-283"},"PeriodicalIF":0.0,"publicationDate":"1997-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80749676","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}
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