Pawel Pieranski,   S. Popa-Nita,   T. Ploetzing   and C. Even Universite Paris-Sud,   Laboratoire de Physique des Solides,   France "Asymmetric shapes of crystals in temperature gradient" Fig: Shapes of L1-in-Pn3m inclusions in equilibrium and in temperature gradients. http://www.lps.u-psud.fr/Collectif/gr_15/Soft_Crystals_Frame.htm    Thanks to their unusual structures and properties, the lyotropic liquid crystal phases raise interesting issues to the faceting of crystals. It has been pointed out previously that faceting of cubic lyotropic liquid crystals, in equilibrium with isotropic liquid or vapour phases, can be either very rich [1] or poor [2] depending on the interfacial tension [3].    Here, we focus on effects of temperature gradients on shapes of the interface between the L1 and cubic Pn3m phases in the mixture C12EO2/water.    We show that the symmetry of the crystal habit is broken even by a very temperature gradient (see figure above). [1] P. Pieranski, P. Sotta, D. Rohe and M. Imperor-Clerc, Phys. Rev. Lett.84, 2409 (2000) [2]P. Pieranski, S. Popa-Nita, T. Ploetzing and C. Even ,submitted to EPJE [3] P. Nozires, F. Pistolesi and S. Balibar, EPJE 24, 387 (2001)

P. Jakubczyk and M. Napiorkowski Institute of Theoretical Physics,   Warsaw University,   Poland "Adsorption in a non-symmetric wedge" We study adsorption in a non-symmetric wedge consisting of two chemically different, homogeneous planes. First, we macroscopically analyse configurations of non-volatile liquid drop placed in such two-dimensional wedge and construct phase diagram describing transitions between various interfacial shapes. Then adsorption is discussed within MFT based on the effective interfacial Hamiltonian. Two regimes for the system parameters - the wedge opening angle (phi) and the critical wetting temperatures of each of the planar walls (TW1 and TW2, TW2 < TW1) - are identified. In one of them we find the critical filling transition at TF < TW2 and the corresponding critical indices which are equal to those found for a symmetric wedge. In the other regime TW2 < TF < TW1 interfacial configurations are similar to those exhibited in the case of a planar substrate consisting of two chemically different parts. In the borderline case TF = TW2 the interface profile above the wall with the lower wetting temperature becomes parallel to it. The line tension expressions are derived.

Piotr Garstecki Department of Chemistry and Chemical Biology,  Harvard University,   USA "Dynamic self-assembly of micron-scale bubbles" We use a microfluidic flow-focusing geometry to form monodisperse gas bubbles in micrometer size range. We propose a quantitative description of the steady state, periodic breaking of the gas thread in an elongational shear flow. In a broad range of the liquid and gas pressures applied to the system we observe dynamic assembly of the bubbles produced in our device into highly ordered, flowing lattices. The geometry of the lattices can be easily adjusted by tuning the fluid flow rates. Figure:- Examples of the bubble containing fluid flow and lattices formed in a device with the outlet channel widht w=750um. The height of the channel is 28um and the width of the orifice is wor=30um. The numbers to the left of the pictures give the respective flow rates of the aqueous phase (in mL/h). The gas pressure is fixed to 4 psi above the atmospheric pressure. The fluid flows from left to right.

Tobias Ploetzing Universite Paris-Sud,   Laboratoire de Physique des Solides,   France "Ratchet-like behaviour of the shape of liquid crystals" In our topical work, shapes of the interface between the L1 and cubic Pn3m phases in the mixture C12EO2/water are studied. The concave and convex variants are considered on examples of Pn3m crystals surrounded by the L1 phase and of L1 inclusions on surfaces and in the bulk of the Pn3m phase. It is shown that both variants of the Pn3m/L1 interface contain the (111)-type facets coexisting, through angular junction, with everywhere else rough surfaces. We study the evolution of the Pn3m crystals, surrounded by the L1-phase, during saw-tooth-like temperature variation. We point out, that the rough parts of the crystal surface are progressively eliminated for the benefit of growing facets.

Bostjan Markun and S. Zumer Department of Physics, University of Ljubljana,   Slovenia "Pseudo-Casimir force in chiral Smectic Liquid Crystals" Fluctuations in confined systems are strongly affected by the presence of bounding surfaces. The confinement modifies the spectrum of fluctuations which in turn induces an interaction between the boundaries. This fluctuation-induced interaction was initially predicted by Casimir in 1948 [1] for the case of vacuum fluctuations of EM field and is nowadays commonly referred to as a (pseudo) Casimir force. The Casimir interaction is a universal phenomenon present in every system where fluctuations of some physical field are affected by confinement [2]. Previous studies of the pseudo-Casimir force in liquid crystals mostly addressed nematic systems [3,4]. In this contribution we present a theoretical study of the pseudo-Casimir force in two confined chiral smectic systems with a simple planar geometry: a homeotropic cell and a free-standing film. We consider the pseudo-Casimir force induced by fluctuations of the orientational order and focus on the behaviour of the force in the vicinity of the SmA* to SmC* phase transition. We demonstrate how the character of the force depends on the type of fluctuation modes and analyse the effect of different anchoring strengths at the confining substrates. The latter is especially interesting as it can lead to non-monotonous force profiles and can cause the force to change sign. We present an example of a frustrated system where the competition between the surface induced ordering and the internal smectic field enhances fluctuations which eventually results in the divergence of the pseudo-Casimir force at the SmA* to SmC* transition. In non-frustrated systems, such as free-standing smectic films, the amplitude of the force at the SmA* to SmC* transition is increased, but it does not diverge. References: 1. H. B. G. Casimir, Proc. Kon. Ned. Akad. Wet. 51, 793 (1948) 2. S. K. Lamoreaux, Am. J. Phys. 67, 850 (1999) 3. P. Ziherl, R. Podgornik, and S. Zumer, Chem. Phys. Lett. 295, 99 (1998) 4. P. Ziherl, F. K. P. Haddadan, R. Podgornik, S. Zumer, Phys. Rev E 61, 5361 (2000)

M. Kalininaa, V.Arslanova, N. Novickovab and S. Zheludevab aInstitute of Physical Chemistry,  Russian Academy of Sciences,  Russia bInstitute of Crystallography,  Russian Academy of Sciences,  Russia "Monolayers and Langmuir-Blodgett films of amphiphilic cyclen" The relationship between the extent of molecular organization, assembly dimensionality and physical-chemical properties of the system is one of the most fundamental and exiting problems in modern physical chemistry of the interfaces. Ordered ultra-thin films such as Langmuir monolayers or LB films containing amphiphilic macrocyclic ligands are of particular interest due to receptor characteristics of ionophores. This feature allows one to reveal the role of inherent properties of the interface and structure of thin film in the important processes in planar system such as molecular recognition. Dicetyl cyclen (DCC) as one of the amphiphilic macrocyclic tetra-amines has been found to form stable monolayers at the air/water interface and LB films on different solid platforms. Kinetic data, obtained by surface pressure monitoring suggest that the rate, the mechanism and the very possibility of complex formation in DCC monoalyers are strictly dictated by ligand conformation and protonation degree at the interface. On the basis of monolayer compression isotherms and X-ray fluorescence spectra of corresponding LB-films we have shown the strong effect of the interface on sensitivity and selectivity in metal ion recognition by DCC immobilized in monolayers. The immobilization of macrocycles on the surface of liquid can be considered as "induced preorganization" leading to unusual behavior of the ligands such as selectivity inversion of DCC for Ni(II) and Cu(II) ions in monolayers. Several cycles of complex formation- decomplexation can be repeated in monolayer under soft conditions by changing of subphase pH without the disruption of film structure. In contrast to the behavior of binary systems (epoxy oligomer/triethyltetraamine or epoxy oligomer/DCC), effect of DCC self-organization in 2D cross-linked matrix of ternary system (epoxy oligomer, triethyltetraamine and DCC) at the air/water interface was revealed by use of AFM microscopy. The influence of the structure of these films on the recognition of metal cations discussed also. The quartz crystal microbalance method was demonstrated to determine quantitatively the presence of Cu(II) in water solutions with ions concentration as low as 10-8M by using quartz crystals coated with dicetyl cyclen Langmuir-Blodgett film. The treatment with dilute acid to clarify the LB film from metal ions allows detectors of this kind to be used many a times. Based on all represented results monolayers and LB films incorporating amphiphilic macrocyclic polyamines are reasonably considered to hold much promise for their potential application as units in sensor devices.

Sylwester Przybyl,  Justyna Marchwiak ,and   Piotr Pieranski Poznan University of Technology,   Poznan,   Poland "Closely packed helices" Real knots, in contrast to topological knots, are tied on real ropes. Real rope have finite diameters what puts a lower limit on the knot length. A basic question arises: Which is the conformation of a knot of a given topological type at which the rope length reaches its global minimum ? Looking for the answer we performed a series of numerical experiments in which the (ideal) rope, on which knots have been tied, is shortened. In the case of torus knots the path leading to the minimum length conformations passes through a phase at which the knots can be seen as built from the closely packed helices. We present basic properties of the structures. We present their basic properties. Structure of the (2,5) torus knot tied on the ideal rope

Marcin Fialkowski,  Robert Nowakowski,  and Robert Holyst Institute of Physical Chemistry,  Polish Academy of Sciences,   Warsaw,   Poland "PdHx formation on palladium thin films: morphological study" A two-dimensional ridge pattern formed on the surface of thin palladium film in the process of palladium hydride formation at 298 K has been studied. A mechanism to explain the observed metric properties of the ridge pattern morphology has been proposed. Formulas for distribution of domain areas and circumferences have been derived from the maximum entropy principle. They fit very well the experimental data.

S. Kondrat,  A. Poniewierski,  and L. Harnau Institute of Physical Chemistry,  Polish Academy of Sciences,   Warsaw,   Poland "A nematic liquid crystal confined between inhomogeneous substrates" A nematic liquid crystal confined between two identical flat solid substrates, with an alternating stripe pattern of planar and homeotropic anchoring, is studied in the framework of the Frank-Oseen theory. By means of numerical minimization of the free energy functional we study the effect of the sample thickness D on the location of the phase transition between a uniform alignment, either planar or homeotropic, and a distorted nematic texture. The solvation force f due to distortions of the nematic director is also studied. It is found that f is always attractive, and for D small compared to the periodicity of the surface structure it exhibits two distinct asymptotic behaviors:  f ~ -D-1/2  or  f ~ -D-1,  depending on the relation between D and the extrapolation lengths.

Volodymyr Babin   and Alina Ciach Institute of Physical Chemistry,  Polish Academy of Sciences,   Warsaw,   Poland "Bicontinuous cubic phases confined in slit-like pores" We consider the impact of the connement on the double-diamond cubic phase (D phase) in the slit-like pores. We investigate the response of the D phase to the external stress (expansion or compression). We pay particular attention to mechanical properties and to structural deformatuions for different orientations of the confining surfaces with respect to the unit cell. We study the effects of confinement far and close to the phase coexistence with the lamellar phase. We want to find out which properties of the confined cubic phases are the same as in simple fluids, which phenomena are characteristic for periodic structures and whether there are features specic only for the three-dimensional structures.

Olgierd Cybulski Institute of Physical Chemistry,  Polish Academy of Sciences,   Warsaw,   Poland "Minimization of the Renyi entropy production in the Fleming-Viot process" We analyze the Fleming-Viot process. The system is confined in a box, whose boundaries act as sink of Brownian particles. The death rate at the boundaries is matched by the branching (birth) rate in the system and thus the number of particles is kept constant. We show that such a process is described by the Renyi entropy whose production is minimized in the stationary state. The entropy production in this process is monotonically decreasing function of time irrespective of the initial conditions. The first Laplacian eigenvalue is shown to be equal to the Renyi entropy production in the stationary state. As an example we simulate the process in a two dimensional box.

C. Even, M. Imperor, C. Bonnoit, A. Gourbil, P. Pieranski, M. Veber Universite Paris-Sud,   Laboratoire de Physique des Solides,   France "Rich faceting of droplets in cubic phase" Liquid crystals sometimes exhibit crystalline cubic phases in their phase diagram. This is true both for lyotropic and thermotropic liquid crystals. Lyotropic cubic phases, when deposited on a glass plate such as to form droplets, develop a huge number of facets, some of them having high Miller indices, forming a so-called "Devil's staircase faceting". [1] Droplets of a thermotropic cubic phase also display a very important number of facets. Their advantage upon lyotropic phases is that they do not need to be kept in a controlled humidity atmosphere, and thus they can be handled more easily. Among their physical properties, we can quote the following ones : the lattice parameter is about 10 nm, the surface tension (in a gaseous atmosphere) is the usual value for ordinary liquids, i.e. several 10 mN/m., and the Young modulus is low (soft matter), about 105 N m-2 Our main topic of interest concerns answering the following question : why are these phases so richly faceted? A theoretical model has been developed by Nozi?res et al., trying to explain the rich faceting of these phases [2]. We are trying to test this model experimentally. The molecule we use in synthetized in our lab, and the phase diagram is characterized using X-rays and observations with a polarized microscope. The cubic phase is stable between approx. 100°C and 140 °C, and is metastable down to room temperature. This property allows us to study the droplets at a lower scale using an Atomic Force Microscope, at room temperature. We have already observed individual steps on principal facets, and also systems of parallel steps on other facets [3] (see picture a). We have also realized observations under the microscope, of how the cubic phase grows from the liquid isotropic one, and how the facets evolve inside the stable temperature range of the cubic phase and discovered a so-called "pseudo-growth" of the facets (see picture b)   a)   AFM pictures : left : different facets (picture size 20mm) ; right : steps on a principal facet (picture size1 mm)   b)   optical pictures : pseudo-growth of facets when T goes down, inside the cubic phase [1] P. Pieranski, P. Sotta, D. Rohe and M. Imperor-Clerc, Phys. Rev. Lett.84, 2409 (2000) [2] P. Nozires, F. Pistolesi and S. Balibar, Eur. Phys. J. B. 24, 387 (2001) [3] C.Even, A.Gourbil, M. Imperor-Clerc, P. Pieranski and M. Veber Chem. Phys. Chem.12, 1031 (2002)

a) b)

J. Widoniak, S. Eiden and G. Maret Department of Physics,   University of Konstanz,   Konstanz,   Germany "Synthesis and Characterisation of porous and non-porous TiO2 - Colloids " The importance of well-defined particles has been recognized in a number of applications, for example, in ceramics, pigments, solar cells and, more recently, as building blocks of photonic crystals. Titania particles are particularly interesting with regard to their high refractive index. Monodisperse spherical TiO2 particles with diameters from 200 nm to 3000 nm were prepared by controlled hydrolysis of titianium tetraethoxide in ethanol. Ethanol was mixed with 0.1 M aqueous salt or polymer solution. After that, titianium tetraethoxide was added at ambient temperature under stirring. Depending on the concentration, precipitation occurred after a few seconds or minutes and homogeneous TiO2 beads were formed. After two hours, the reaction was finished and the spheres were filtered and washed with ethanol. The characterisation of this spheres was mainly done by SEM.

Scanning electron micrographs reveal the perfectly uniform spherical shape of the TiO2 particles (Fig.1). The size and the size distribution were affected in a rather sensitive way by different ions or polymers which were added to the reaction solution. Transmission electron microscopy and measurements of the specific surface aera by BET showed that addition of polymer yielded porous colloids. We investigated the influence of different polymers and their concentrations on the porosity of colloids. The polymer molecules caused a sterical stabilisation of the colloids. Similarly, the electrostatic stabilisation of the particles was caused by the ions of the added salt. This was determinated by electrophoretic measurements. Fig. 1: SEM of the titania beads 1

The X-ray powder diffraction pattern showed that the obtained TiO2 phase was amorphous. The particles can be sintered at 400°C and 1000°C in order to obtain anatase and rutile particles, respectively. In order to get optimal results we figured out the mechanism of formation of the colloidal particles. Based on the results of AFM and HR TEM, it was possible to make some statements about the growth mechanism and the structure of the colloids. At the beginning, particles of about 4 nm to 10 nm are formed by the addition of titaniumhydroxid monomeres. After that, they aggregate and become colloids with a size of up to 3000 nm.

K. Bucior,   A. Patrykiejew,   S. Sokolowski i   O. Pizio Department of Chemistry,   University of Maria Sklodowska-Curie,   Lublin,   Poland "Liquid liquid interface in a binary mixture of associating fluids exhibiting a closed-loop immiscibility" We investigate the structure and thermodynamic properties of the liquid liquid interface for a two-component mixture of associating fluids, exhibiting the closed-loop liquid-liquid immiscibility. In the study we apply the density functional approach and evaluate the density profiles, the ratio of unbound particles and the surface tension in order to investigate how those properties depend on the association energy.

Daniela Tsekova   and Christo Nanev Institute of Physical Chemistry,   Bulgarian Academy of Sciences,   Bulgaria "Experimental Observations of Formation, Dissolution, Mechanical Properties and Some Morphological Peculiarities of Tetragonal Lysozyme Crystals " The crystallization of Hen Egg White Lysozyme (HEWL), 25 mg/ml, has been investigated applying temperature changes, between -2° and 30°C, and varying NaCl concentration from 3M to 5M in 0.05 M sodium acetate buffer. At -2°C we observed specific "initial growth form" for HEWL crystals (2 hours after solution preparation). Very small "crystals" had a shape of semi-sphere instead of the four {101} faces. During long dissolution we observed the appearance of teeth forms, i.e. periodical gorges directed along the {001} planes that suggests weaker bonds between these planes. Anisotropy in the mechanical properties of the lysozyme crystals also has been established. Unusual crystal morphology when lysozyme crystals grow in a thin cell (65 ?m) has been observed. A new artificial face {101} appears instead of the pyramid formed by the four {101} faces, in case when a crystal grow with c-axis perpendicular to the substrate. Easier growth in the planes {101} (under starvation conditions) is a result of a stronger bonding in these planes, compared to the bonding between them, evidently.

Pawel Bryk Department of Chemistry,   University of Maria Sklodowska-Curie,   Lublin,   Poland "Density functional theory for colloidal rod-polymer mixture" A density functional theory for a mixture of hard rods and polymers modeled as chains built of hard tangent spheres is proposed. The polymeric contribution is taken into account by using a theory developed by Yu and Wu (J. Chem. Phys. 116, 7094, (2002)) whereas for the rod contribution a density functional theory of Schmidt (Phys. Rev. E 63, 50201, (2001)) is used. After a formal derivation bulk phase diagrams are analyzed. It is found that the critical packing fraction decreases as the chain length increases. This shift is most noticable for short chains. For very long chains the reduced critical density of the reservoir needles tends toward a value of 2.5526. References: [1] Y.-X. Yu and J. Wu, J.Chem.Phys. 116 , 7094 (2002). [2] M. Schmidt, Phys.Rev.E 63, 50201 (2001). [3] J.M. Brader, A. Esztermann and M. Schmidt, Phys.Rev.E 66 31401 (2002). [4] P. Bolhuis and D. Frenkel, J.Chem.Phys. 101, 9869 (1994).

A.Ciacha G.Stellb, W.T.Gozdza and R.Evansc aInstitute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland bState University of New York at Stony Brook, USA cH.H.Wills Physics Laboratory , University of Bristol, Bristol, UK "FROM LIVING POLYMERS TO IONIC CRYSTALS - field theoretic approach to ionic systems" Ionic solutions are studied within Landau-Ginzburg-Wilson type of functional. Charge-charge correlation function in the diluted phase is determined and its connection to 'livig polymers' is discussed. Effects of fluctuations on ion-diluted - ion-dense and order-disorder phase transtions are described. The fluctuation-induced first-order order-disorder transition is identified with the process of ionic-crystal formation. The bcc crystal can be viewed as close-packed frozen chains of 'livig polymers'.

Malgorzata Graca,   Stefan Wieczorek,   and Robert Holyst Institute of Physical Chemistry,  Polish Academy of Sciences,   Warsaw,   Poland "Growth of Polystyrene domains in Isotropic, Nematic and Smectic Phase of 8CB Liquid Crystal" The growth pf polymer domains in the isotropic, nematic and smectic matrices is studied by the light scattering. In the smectic and isotropic matrices the growth is diffusive, and in the nematic matrix it is influenced by the elastic forces. The scaling is obeyed. A crossover to the wetting fast-mode hydrodynamic regime is also observed at long times. In order to perform these measurements we had to eliminate the multipe scattering of light.