Growth and shapes of a cubic lyotropic liquid crystal

Abstract

Monocrystals of the cubic lyotropic liquid crystal phase V1 are studied in droplets of the mixture C12EO6/water surrounded by water vapor of controlled pressure p. Shapes of monocrystals are found to depend on the conditions of growth from the lamellar phase and on the nature of the substrate. After the growth, when the lamellar phase is exhausted and crystals are in equilibrium with water vapors, their shapes are shown to depend on the pressure p. Thermodynamic aspects of these phenomena are discussed. PACS. 64.70.Md Phase transitions in liquid crystals -82.65.Dp Thermodynamics of surfaces and interfaces

Pawel Pieranski – crystallographer of liquids and Alfred-Saupe-prize laureate 2019

“…Another fascinating observation was made, when liquid single crystals [Figure 3(i-j)] or soft single crystals [Figure 3(k-l)] were grown in a gas environment. In this case, a huge number (up to 60) of different kinds of facets were observed [40,53,54], including facets corresponding to large Miller indices, which are rarely found in solid crystals. This devil's staircase scenario [53] was actually expected to appear in solid crystals close to 0 K. This very unusual observation could be explained by striking differences in the roughening temperature T r , above which the smaller facets disappear.…”

“…In the 1990s, Pieranski was among the first who applied atomic force microscopy (AFM) for studying the surface topography of glass-like liquid crystals [37][38][39] and soft crystals [40,41], a method which is widely used today. His research interests in freely suspended LC films [42][43][44][45][46][47][48][49][50][51][52], faceting (next paragraph) [20][21][22][23][53][54][55][56][57][58][59][60][61], cellulose [62][63][64][65] or the dowser texture [71][72][73] have been less frequently shared by other researchers, but probably their crack of dawn is still ahead.…”

“…Hitherto, Pawel Pieranski's most long-lasting continuous research interest over many decades was devoted to the growth and thorough investigation of liquid single crystals, i. e. droplets of liquid crystals, which do not show a spherical shape but exhibit facets, thereby resembling the shape of solid crystals (Figure 3). His studies included colloidal crystals [15], thermotropic liquid crystalslike blue phases [20][21][22][23] and thermotropic bicontinuous cubic phases [40,41] as well as lyotropic cubic liquid crystals [53][54][55][56][57][58][59][60][61]. To grow liquid single crystals, Pieranski developed special containers for the specimen, where either the temperature and a temperature gradient [21,27,61] or the humidity of the environment [53][54][55][56][57][58][59][60][61] can be controlled very precisely.…”

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Commemorating Alfred Saupe, an outstanding pioneer of liquid crystal research, the Alfred-Saupe-Foundation and the German Liquid Crystal Society bestow the Alfred Saupe Prize to honour outstanding work in the field of liquid crystals. On 28 March 2019, Prof. Dr Pawel Pieranski received this prize, which includes the Alfred Saupe Medal (Figure 1), in recognition of his outstanding works in the field of liquid crystal research and its application.Pawel Pieranski has worked extensively in many different areas of liquid crystal (LC) research, such as the static and dynamic behaviour of nematic LCs [1-8], chiral smectic and especially ferroelectric LCs [9-11], colloidal crystals [12][13][14][15][16][17][18][19], cholesteric and blue phases [20][21][22][23][24][25][26][27][28][29][30][31][32], wetting and anchoring [33][34][35][36], application of atomic force microscopy (AFM) to LCs [37-41], freely suspended LC films [42-52], shapes of single crystals [53][54][55][56][57][58][59][60][61], cellulose derivatives [62][63][64][65], and various aspects of order, structure, symmetry, defects and topology in certain mesophases or special geometries [66]

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Faceting and stability of smectic A droplets on a solid substrate

“…Large He 4 crystals (i.e., of centimetric size) are also faceted, with the advantage of equilibrating much faster than the former due to their quantum nature (atoms can go through energy barriers by tunneling effect) [6]. Faceted shapes were also observed in soft matter, in particular in the Blue Phases of cholesteric liquid crystals [7][8][9], in the smectic B plastic crystals [10,11], and in the cubic phases of the lyotropic systems [12][13][14][15]. Although we are dealing with monocrystals in all these examples, the real question is always to know whether the shapes observed experimentally are at equilibrium (in a stable or a metastable state), or result from some growth processes.…”