Drying dissipative structures of aqueous solution of poly(ethylene glycol) on a cover glass, a watch glass, and a glass dish

Drying dissipative structures of aqueous solution of poly(ethylene glycol) (PEG) of molecular weights ranging from 200 to 3,500,000 were studied on a cover glass, a watch glass, and a glass dish on macroscopic and microscopic scales. Any convectional and sedimentation patterns did not appear during the course of drying the PEG solutions. Several important findings on the drying patterns are reported. Firstly, the crystalline structures of the dried film changed from hedrites to spherulites as the molecular weight and/or concentration of PEG increased. Secondly, lamellae were formed along the ring patterns especially at high concentrations and high molecular weights. The coupled crystalline patterns of the spherulites and the lamellae were observed in a watch glass along the ring structures, supporting the important role of the convection by the gravity during the course of dryness. The coupled patterns were difficult to be formed on a cover glass and a glass dish, except at the outside edge of the dried film. Thirdly, the size of the broad ring at the outside edge of the dried film especially on a cover glass and a watch glass increased sharply as the molecular weight increased and also as the polymer concentration increased. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Drying dissipative patterns of aqueous solutions of simple electrolytes and their binary mixtures on a cover glass

The drying dissipative patterns of aqueous solutions of simple electrolytes, KCl, NaCl, CaCl₂, and LaCl₃, were observed on a cover glass. The macroscopic broad rings were formed at the outside edge of the drying film area, which shrunk from the initial solution area especially at low salt concentrations. The drying area and the broad ring size decreased as the salt concentration decreased. The microscopic block-like and dendritic cross-like patterns were observed for all the salts. Size of single crystals dried on a cover glass increased as salt concentration increased. The drying patterns of the binary mixtures of the salts were also observed. Size of the broad ring increased sharply by mixing. The microscopic patterns were, on the other hand, insensitive to the mixing.     

Drying dissipative patterns of aqueous solutions of poly (4-vinyl-N-alkyl-pyridinium halide)

Drying dissipative structural patterns of aqueous solutions of poly (4-vinyl-N-alkyl-pyridinium halide) were studied on a cover glass. The broad rings were observed at the outside edge of the dried film. The broad ring size (or the area of the dried film, S) increased as polymer concentration increased. The broad ring size decreased and then turned to increase when the hydrophobicity of the polymers increased. The drying time from the initial liquid (T) was insensitive to the polymer concentration. But, T was sensitive to the kind of polymers, i.e., hydrophobicity of polycations, and roughly in the opposite order to that of S. Spoke-like macroscopic patterns appeared clearly for poly (4-vinyl-N-n-butylpyridinium bromide) (C4PVP), but were not observed clearly for the other polymers. Cross-like microscopic patterns appeared from which the polymers with the extended conformation are deduced to be crystallized during the course of dryness. The cooperative crystallization took place between the polymer and the salt in the C4PVP + KCl mixtures. When two different polymers were mixed, segregation and then independent crystallization of each single component polymers were observed. The dissipative effect is important for determining of the polymer crystal structure during the course of crystallization.     

Dissipative crystallization of aqueous solutions of hydroxypropyl cellulose

Drying dissipative structures of aqueous solutions of hydroxypropyl cellulose, their viscosities of 2 wt.% solutions ranging from 2 to 2,000 mPa.s were studied on a cover glass, a watch glass, and a Petri glass dish. The thickness profile of the dried film shows the coexistence of a low round hill and a high broad ring on a cover glass. The broad ring size increased as molecular weight and/or concentration of the polymers increased on a cover glass and a watch glass. Microscopic drying crystal patterns of HPC changed as a function of the distance from the film center, which is one of the typical results of the dissipative crystallization. Rod-like microscopic drying patterns originated in the cholesteric liquid crystalline structures were observed. The rods oriented mainly parallel and in some case perpendicularly to the radial direction of the dried film except the central area, where the rods distributed at random. These orientation effects were significant for low molecular weight samples and in a watch glass.     

Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboguanylic acid) and poly(ribocytidylic acid)

Drying patterns of aqueous solutions of potassium salts of poly(riboguanylic acid) (KPolyG), poly(ribocytidylic acid) (KPolyC), and their mixtures KPolyG + KPolyC were studied on a cover glass, a watch glass, and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and also in the inner area of the dried film was observed. The fine multiple ring structures formed, which supports the fact that the affinity of the polymer with the substrate is strong. Typical microscopic drying patterns of KPolyG, KPolyC, and KPolyG + KPolyC were spherulites, dendritic long rods, and sword (harberd)-like rods, respectively. The patterns changed depending on the location in the dried film. The dendritic long rods and sword-like rods were assigned to the crystals of double-stranded and/or triple-stranded helices of the G:C and 2G:C complexes. Cross-like drying patterns that originated from the salt-polymer interaction are also observed. The relationship between the polymer complexation of KPolyG + KPolyC systems and the drying patterns is similar to that of KPolyA (potassium salt of poly(adenylic acid)) + KPolyU (potassium salt of poly(uridylic acid)).     

Drying dissipative structures of thermo-sensitive gel spheres of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide)

Drying dissipative patterns were observed at 25 °C, 33 °C, and 45 °C on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of colloidal crystals of the thermo-sensitive gels of poly(N-isopropylacrylamide) (PNIPA). Two kinds of broad rings, i.e., transparent ring at the outside edge and the ring in the inner area from the edge, were observed. Sizes of the former were the same as those of the initial liquids irrespective of gel concentration, whereas sizes of the latter decreased as gel concentration decreased. These broad rings were composed mainly of the monomeric and the agglomerated gel particles, respectively. Formation of the monodispersed agglomerated particles and their ordered arrays in the inner area of the dried film were observed especially on a Petri glass dish and a watch glass. The important role of the electrical double layers formed around the agglomerated particles is supported for the ordering of the agglomerated particles. The essential differences in the drying patterns between PNIPA gel spheres and the typical colloidal particles did not appear.     

Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboadenylic acid) and poly(ribouridylic acid)

Dissipative drying patterns of aqueous mixtures of potassium salts of poly(riboadenylic acid) (KPolyA) and poly(ribouridylic acid) (KPolyU) were studied on a cover glass, a watch glass and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and the inner area of the dried film was observed. The fine multiple ring structures formed when the affinity of the polymer with the substrate is strong. Microscopic drying patterns changed drastically depending on the location in the dried film. Microscopic drying patterns were mainly dendritic long rods and sword (halberd)-like rods. They are assigned to the crystals of double-stranded and triple-stranded helices of the A:U and A:2U complexes, respectively. Cross-like drying patterns are also observed originated from the salt-polymer interaction.     

Sedimentation and drying dissipative patterns of binary suspensions of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying binary mixtures among colloidal silica spheres of 183 nm, 305 nm, and 1.205 μm in diameter in aqueous suspension on a watch glass, a glass dish, and a cover glass, respectively. The broad ring-like sedimentation patterns were formed within several hours in suspension state for all the substrates used. Colorful macroscopic broad ring-like drying patterns were formed for the three substrates. In a watch glass, macroscopic drying patterns were composed of the outer and inner layers of small and large spheres, respectively. The two colored layers were ascribed to the Bragg diffractions of light by the dried colloidal crystals of the corresponding spheres. The width ratio of the layers changed in proportion to the mixing ratio of each spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edges of the broad ring and the inner wall of the cell. On a cover glass, the sphere mixing ratios were analyzed from the widths of the drying broad rings of the small spheres at the outside edge. High and distinct broad rings of small spheres and the low and vague broad one formed at the outer edges and in the inner area, respectively. Drying dissipative pattern was clarified to be one of the novel analysis techniques of colloidal size in binary colloidal mixtures.     

Drying dissipative structures of the aqueous suspensions of palygorskite and tungstic acid particles

Macroscopic and microscopic dissipative structural patterns during dryness of the aqueous suspensions of palygorskite (PGK, needle-like shaped) and tungstic acid (TA, plate-like) have been studied on a cover glass. The coexistence of the broad ring of the hill accumulated with the particles and the round hills is observed around the outside edges of the dried film and in the center, respectively. These patterns differ from those of the suspensions of spherical particles. Furthermore, the spoke-like patterns, which have been observed for the suspensions of the spherical particles so often, are not observed at all for PGK and TA suspensions. These characteristic macroscopic patterns of PGK and TA are quite similar to those of the fractionated and monodispersed bentonites (plate-like) reported previously Yamaguchi et al. (Colloid Polymer Sci 283:1123, 2005). Wrinkled and/or branch-like fractal patterns are observed in the microscopic scale, which are quite similar to those of bentonites. “Shape information” of the colloidal particles is clarified to be “transferred” to the drying patterns via the convectional and sedimentary patterns during the course of dryness.     

Sedimentation and drying dissipative patterns of colloidal crystals of poly(methyl methacrylate) spheres in a glass dish

In a series of our studies on the dissipative structure formation, this work focused on the sedimentation and drying patterns of colloidal crystals of poly(methyl methacrylate) colloidal spheres with different sizes (100, 200, 300, and 1,000 nm in diameter) in a glass dish. During the course of dryness, the brilliant iridescent colors changed. Drying frontier grew from the central area of the cell toward the outside edge. Macroscopic and microscopic drying patterns of the resulting film from dried colloidal suspensions showed outer and inner broad rings. Size of the outer rings increased with increasing sphere concentration but did not altered sphere size, while these factors affected the inner ring size. These observations do not support the pinning effect proposed by Deegan et al.     

Sedimentation and drying dissipative patterns of ternary mixtures of colloidal silica spheres having different sizes

The sedimentation and drying dissipative structural patterns were formed during the course of drying ternary mixtures of colloidal silica spheres of 183 nm, 305 nm, and 1.205 μm in diameter in aqueous suspension on a watch glass, a glass dish, and a cover glass. The patterns were observed by closed-up pictures, metallurgical optical microscopy, 3D profile microscopy, reflection spectroscopy and AFM images. The concentrations of the three spheres ranged from 0.0023 to 0.0128 keeping the same concentrations for each spheres. Broad ring-like sedimentation patterns were formed within a short time in suspension state especially in a glass dish. In a watch glass, colorful three layered ring-like drying patterns were observed and composed of the outer, middle and inner layers of small, medium, and large spheres, respectively. The three colored segregated layers were formed by the balancing between the outward convectional flow and the inward sedimentation of spheres. In a glass dish, wave-like macroscopic drying patterns were observed in the intermediate areas between the outside edge of the broad ring at the central area and the inner wall of the cell especially at low sphere concentrations. The size of the broad ring at the central area increased as sphere concentration increased. On a cover glass, size segregation also took place, i.e., small, medium, and large spheres located at the outer, medium, and central areas, though these segregations were not so complete compared with those on a watch glass.     

Drying dissipative patterns of biological polyelectrolyte solutions

Drying dissipative structural patterns of aqueous solutions of biological polyelectrolytes, sodium poly (α, L-glutamate; NaPGA) and poly (-L-lysine hydrobromide; PLL.HBr), were studied on a cover glass. Below the critical polymer concentration, m* (ca. 0.003 and ca. 0.01 monoM for NaPGA and PLL.HBr, respectively), the dried patterns shrank only around the center of the initial solution area wetted on a cover glass. Above the m* values, on the other hand, the drying pattern extended throughout the initial solution area. The m* values agreed excellently with the critical polymer concentrations, where the surface tensions started to decrease sharply as the polymer concentrations increased. The broad rings were always observed in the drying patterns of any solutions examined. The spoke-like cracks appeared at the polymer concentrations above the m* values and only in the area of the broad rings. Microscopic structures such as cross-like, rod-like, and block-like patterns formed irrespective of polymer concentrations. Especially, the city-road-like microscopic pattern was observed for PLL.HBr solutions, which strongly supports the formation of crystal structures of PLL.HBr that remain in the whole processes of dryness. These patterns were correlated deeply with the crystal-like orientation of the biological polyelectrolytes at the air–solution interfaces.     

Convectional, sedimentation, and drying dissipative structures of black tea in the presence and absence of cream

Convectional, sedimentation, and drying dissipative structures of black tea with and without cream were studied in a tea cup, a cover glass, a watch glass and a glass dish on macroscopic and microscopic scales. The convectional patterns were vigorous and irregular at the initial stage but soon highly distorted Bernard cells grew. The global integrated flows of the tea particles coated with cream at the air–suspension interface were observed vaguely from the central area toward outside edge at the initial stage in a tea cup and a large watch glass, but the flow direction turned oppositely from the outside to the central area. At the similar time, the short and few spoke lines appeared at the outside edge and grew long toward the central area. Then, the cooperative formation of clusters and bundles of the spoke lines took place at the middle and final convectional stages, and then the dynamic sedimentation patterns appeared. The drying patterns of tea with and without cream were composed of the broad ring at the outside edge and a round hill accompanied sometimes with the bundles of spoke lines. These features are consistent with those of suspensions of non-spherical particles. The pinning effect is not always supported by this work, but importance of the gravitational and Marangoni convectional flows is proposed instead. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Drying dissipative structures of Chinese black ink on a cover glass and in a dish

Macroscopic and microscopic dissipative structural patterns are formed in the course of drying a suspension of Chinese black ink on a cover glass and in a dish. The time for the drying and the pattern area increased as the particle concentration increased. The broad ring patterns of the hills accumulated with the particles formed around the outside edges on a macroscopic scale. The height and the width of the broad ring increased as the particle concentration increased. The spokelike patterns of the rims accumulated with particles were also formed on a macroscopic scale. Microscopic patterns of colloidal accumulation were observed over the whole region of the pattern area. Various types of convection cells were observed on a cover glass and in a dish at 25–80 °C. A time-resolved observation of the drying process was also made. The convections of water and the colloidal particles at different rates under gravity and the translational and rotational Brownian movement of the particles were important for the macroscopic pattern formation. Microscopic patterns were determined by the translational Brownian diffusion of the particles and the electrostatic and the hydrophobic interactions between the particles and/or between the particles and the cell wall in the course of the solidification of the particles.     

Drying dissipative structures of cationic gel spheres of lightly cross-linked poly(2-vinyl pyridine) (170 ∼ 180 nm in diameter) in the deionized aqueous suspension

Drying dissipative patterns of cationic gel crystals of lightly cross-linked poly(2-vinyl pyridine) spheres (AIBA-P2VP, 170?～?180 nm in diameter) were observed on a cover glass, a watch glass, and a Petri glass dish. Convectional patterns were recognized with the naked eyes. Two kinds of the broad rings were observed at the outside edge and inner region in the macroscopic drying pattern, and their size at the inner regions first decreased and then turned to increase as gel concentration decreased. Formation of the similar-sized aggregates, i.e., hierarchical aggregation and their ordered arrays were observed. This work supported strongly the formation of the microscopic drying structures of (a) ordered rings, (b) flickering ordered spoke-lines, (c) net structure, and (d) lattice-like ordered structures of the aggregated particles. The ordering of the similar-sized aggregates of the cationic gel spheres (AIBA-P2VP) in this work is similar to that of the large cationic gel spheres of poly(2-vinyl pyridine) (385?～?400 nm in diameter) and further to that of the anionic thermosensitive gel spheres of poly(N-isopropyl acrylamide). Role of the electrical double layers around the aggregates and their interaction with the substrates during dryness are important for the ordering. The microscopic drying patterns of gel spheres were different from those of linear-type polymers and also from typical colloidal hard spheres, though the macroscopic patterns such as broad ring formation were similar to each other.     

Drying dissipative structures of thermosensitive gel spheres of poly (N-isopropylacrylamide). Influence of gel size

Drying dissipative patterns of de-ionized suspensions (colloidal crystal-state at high concentrations) of the thermosensitive gels of poly (N-isopropylacrylamide) with various sizes (ca. 400–1,500?nm in diameter at 20?°C) were observed at 20 and 45?°C on a cover glass, a watch glass, and a Petri glass dish. The broad rings were observed and their size decreased as gel concentration decreased. Formation of the monodispersed agglomerated particles and their ordered arrays were observed irrespective of gel size. The macroscopic flickering spoke-like patterns were observed for the gel spheres from 70 to 600?nm in diameter at 20?°C, but almost disappeared for extremely large spheres, poly(N-isopropylacrylamide)(1500-5). This work clarified the formation of the drying microscopic structures of (a) ordered rings, (b) flickering ordered spoke lines, (c) net structure, and (d) lattice-like ordered structures of the agglomerated particles. The ordered rings became rather vague as gel size increased. The large net structures formed so often for large gels. Size effect on the lattice patterns was not recognized so clearly. The role of the electrical double layers around the agglomerated particles and the interaction of the particles with the substrate surfaces during dryness are important for the ordering. The microscopic drying patterns of gel spheres were quite different from those of linear type polymers and also from typical colloidal hard spheres, though the macroscopic patterns such as broad ring formation at the edges of the dried film were similar to each other.     

Sedimentation and drying dissipative patterns of colloidal silica (305 nm in diameter) suspensions in a glass dish and a watch glass

Sedimentation and drying dissipative structural patterns formed in the course of drying colloidal silica spheres (305 nm in diameter) in aqueous suspension have been studied in a glass dish and a watch glass. The broad ring sedimentation patterns formed within several tenth minutes in suspension state by the convectional flow of water and colloidal spheres. The sedimentary spheres always moved by the convectional flow of water, and the broad ring patterns became sharp with time. The width of the broad rings was sensitive to the change in the room temperature and/or humidity. In other words, the patterns became sharp or vague when the room parameters decreased or increased. Colorful macroscopic drying structures were composed of a broad ring and the wave-formed patterns. Iridescent colored fine patterns formed in the solidification processes on the bases of the sedimentation patterns. Beautiful drying patterns were observed for the suspension mixtures of CS300 and NaCl, and were different from the structures of CS300 or NaCl individuals, which support the synchronous cooperative interactions between the colloidal spheres and the salt.     

Dissipative crystallization of potassium salt of poly(riboadenylic acid)

Dissipative patterns during the course of dryness of aqueous solution of potassium salt of poly(riboadenylic acid) (KPolyA) in the presence of potassium chloride were studied on a cover glass, a watch glass and a glass dish. Accumulation of KPolyA polymers forming the broad ring area and the drastic change in size and shape of the polymer single crystals depending on the location of the dried film, which are the typical effects of the dissipative crystallization, took place. Polymer crystals formed were spherulites, dendritic and rod-like assemblies, which are composed of the single or double helical chains depending on the pH-value of the initial solution.     

Drying dissipative structure of sodium dextran sulfate in aqueous solution

Drying dissipative patterns were observed at room temperature on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous solution of sodium salts of dextran sulfate (NaDSS) having molecular weights of 5000, 36,000 ~ 50,000 and 500,000. These biopolyelectrolytes are one of the typical polysaccharides. The influences of the hexose units upon the macroscopic and microscopic drying patterns are studied. Formation of some ordered structure is observed for NaDSS in high polymer concentrations especially on a cover glass. Broad ring size decreased as polymer concentration decreased and/or its molecular weight increased. Drying patterns are clarified to be formed by the successive and cooperative pattern formation of convection, sedimentation, and solidification.