Solvent-driven dewetting and rim instability

We report a series of experimental works about the drying process of polymer solution droplets. Our aims are to analyze the local polymer transport in the drying droplet and to precisely control the profile of polymer film formed after the droplet dries up. For the analysis of the polymer transport, we have established a dynamical observation method for the polymer concentration field by combining the fluorescence microscopy with the lateral profile observation. We observed that a large spatial inhomogeneity of the polymer concentration grows inside the droplet which is caused by the outward capillary flow. For the control of the film profile, we proposed two methods: adding the small amount of surfactant and switching between the solvent evaporation and condensation. These two processes enable us to make a polymer film having a flat profile. Our results propose effective suggestions for controlling the fabrication process of polymer films in inkjet-printing technologies.

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“…14 was previously observed in the dewetting of polymer films 39,40) and in the Plateau-Rayleigh instability in polystyrene troids 41) .…”

Section: Discussionmentioning

confidence: 81%

Dynamics of Drying Process of Polymer Solution Droplets: Analysis of Polymer Transport and Control of Film Profiles

Kajiya

Doi

2011

J. Soc. Rheol., Jpn

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“…44 In the present systems, for all samples, we found that S o 0 for each sample, in principle, a dewetting phenomenon occurred during the drying of the sophorolipids film. 99 In addition, Lee et al 100 have demonstrated that dispersive forces would stabilize the film while polar ones would induce dewetting. There were two dewetting processes that could happen: spinodal dewetting or heterogeneous nucleation.…”

Section: Discussionmentioning

confidence: 99%

Surface-induced assembly of sophorolipids

Peyre

Hamraoui

Faustini

et al. 2017

Phys. Chem. Chem. Phys.

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The surface self-assembly properties of acidic sophorolipids, a bolaform microbial glycolipids with pHresponsive properties in solution, were studied based on the chemical nature of the support and pH of the solution. Sophorolipids generally form micelles in water but formation of morphologies like platelets and twisted fibers depending on pH have also been reported. The surface self-assembly was achieved using dip-coating on three different substrates namely gold, silicon(111) and TiO 2 anatase. Deposition conditions (dip-coating withdrawal speed, relative humidity, temperature) were tested, and it was found that optimum self-assembly occurred at a withdrawal speed of 1 mm s À1 , T of 25 1C and relative humidity of 25%. The local structure of the sophorolipid films was characterized by Atomic Force Microscopy, while Scanning Electron Microscopy was used to characterize the spatial homogeneity. We also attempted to correlate dispersive, electron donor and electron attractor surface energy components, using Good-Van Oss's approach, and the behavior of sophorolipids. We found that when the surface energy is dominated by dispersive components, sophorolipids spontaneously assemble into entangled needles at all pH values (4, 6 and 11). However, when the surface energy is dominated by electronic components, pH has a strong influence on the surface self-assembly. We could discriminate three major organizations: homogeneous layer, isolated aggregates and a two-dimensional network similar to block copolymer surface self-assembly.

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“…For the further treatment it is necessary to consider the polymer solution film thickness l. This thickness established ex- perimentally as ∼1 µm is on one hand sufficiently large in order to neglect intermolecular forces, acting between the polymer solution and the substrate [12], and on the other hand it is sufficiently small to ignore the gravity. Indeed, the criterion l l c is fulfilled, where l c is the critical thickness introduced by de Gennes and given by [22]:…”

Section: Patterning Under Evaporation Of a Poor Solventmentioning

confidence: 99%

“…Dewetting of polymer solutions is accompanied with a variety of physical processes, which were studied extensively in both theoretical and experimental aspects [11,12]. The practical interest to the dewetting of polymer solutions was stipulated by the possibility to create micro-and nanometrically scaled structures.…”

Section: Introductionmentioning

confidence: 99%