Structural Development of Nanoparticle Dispersion during Drying in Polymer Nanocomposite Films

etc., and the interplay between different processes determines the final structure of the dried materials.Here, we report recent advances of selfassembled structures induced by uniform evaporation, examples including drying in a thin-film geometry or evaporating a spherical droplet on a superhydrophobic surface. [4] In these situations, the structure formation takes place in the direction of the evaporation. This excludes the case where lateral flow is induced by nonuniform drying. The lateral flow is important in explaining the coffee-ring effect, where excellent reviews exist in literature. [5,6] After introducing the general procedure in experiments, we explain the physical mechanisms responsible for the structure formation in solvent evaporation. We then discuss recent advances based on single-and binarycomponent solutions, with a special emphasis on the theoretical approaches. Drying of Single-Component SolutionsA general experiment starts with spin-coating a thin-film solution on a substrate, then the sample is left to dry. In the first step, it is important that the spin-cast film is uniform. [7,8] In the second step, the evaporation flux, i.e., the mass removed from the liquid phase to the vapor phase in unit time from unit surface area needs to be controlled precisely. Even for the pure solvent evaporation, the process is complex and involves the diffusion of solvent molecules in both the liquid and vapor phases, and external flow in the vapor phase to prevent saturation. The evaporation flux can be computed using the Hertz-Knudsen equation that is based on the thermodynamics variables [9][10][11] or solving the diffusion equation in the vapor phase using suitable boundary conditions. [12][13][14] The solvent evaporation drives the free surface to recede toward the substrate, resulting in an accumulation of the solutes at the surface. Two competing processes determine the spatial distribution of the solutes. One is the Brownian motion, which is characterized by the diffusion constant D of the solutes. The other is the evaporation, characterized by the rate v ev at which the free surface recedes. Two timescales are related to these two processes: the diffusion time τ D =  2 /D, where  is a characteristic length and the evaporation time τ ev = /v ev . To quantify the relative importance between the diffusion and the evaporation, one can define a dimensionless number called film formation Peclet number: [15]

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Section: Adv Mater 2017 29 1703769mentioning

confidence: 99%

Structure Formation in Soft‐Matter Solutions Induced by Solvent Evaporation

et al. 2017

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“…The zeta potential () and adsorption amount of PVOH on the SiNP surface ( ) was evaluated by varying suspension pH, as shown in Fig.1 (Kim et al 2016). A PVOH chain is adsorbed onto the SiNP surface by the hydrogen bonding of protonated silanol group (-SiOH) in SiNP and hydroxyl group (-OH) in PVOH chain.…”

Section: Sinp-pvoh Interactionmentioning

confidence: 99%

“…The authors previously studied the structure of dried silica-PVOH coating at a limited PVOH between 4 wt.% and 5 wt.% (Kim et al 2016). To further understand the effect of PVOH on the coating structure, here the silica-PVOH coating was tested over a wider range of PVOH from 3.5 wt.% to 7.5 wt.%.…”

Section: Microstructure Of the Silica/pvoh Coatings After Dryingmentioning

confidence: 99%

“…The role of particle-polymer interaction on structural evolution during drying and the resulting particle distribution in SiNP-PVOH coatings has been investigated previously (Kim et al 2009(Kim et al , 2016Lee et al 2017). However, these studies were rather focused on the mechanism of drying behavior, and thus did not contribute much information on the property and structure of resulting dried coatings.…”

Section: Introductionmentioning

confidence: 99%

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Particle Dispersion in Silica-Poly(vinyl alcohol) Coatings: Role of Particle-Polymer Interaction

et al. 2018

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Silica nanoparticle (SiNP)-poly(vinyl alcohol) (PVOH) coating is an important material system in paper coating applications, where particle distribution critically affects coating performance. In the present study, the authors investigated a role of physicochemical interaction between SiNP surface and PVOH chain in SiNP distribution in the coating layer, with a comparison of the suspension at pH 3 (good interaction) and pH 10 (poor interaction) as PVOH concentration was varied. Rheological properties and sedimentation behavior of the suspensions showed the dispersion stability of SiNP at pH 3 was improved by the addition of PVOH, whereas it was independent of the PVOH concentration at pH 10. Scanning electron microscopy and small angle x-ray scattering intensity of dried coating layer showed the uniform and dense structure with homogeneous distribution of SiNPs at pH 3, where spatial arrangement of SiNPs depended on the addition of PVOH. However, non-uniform and porous structures with SiNP aggregates were observed at pH 10, where the spatial arrangement of SiNPs was independent to the addition of PVOH. The stress development during drying of the coating suggested that the mechanical property was related to the spatial arrangement of individual SiNPs at pH 3, whereas to the distribution of SiNPs aggregates at pH 10.

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“…In the fabrication process of nanofibers containing magnetic nanoparticles, controlling nanoparticle dispersion in the nanofibers is one of the important issues to be overcome. In recent research, the influence of surface treatment on nanoparticles on its dispersibility has been reported in films [9] and bulks [10] materials, but not in nanofibers. Suppression of agglomerate formations of magnetite is important when fabricating nanofibers containing magnetic nanoparticles.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Magnetite/Pla Composite Nanofiber Sheet and Evaluation of Its Mechanical Properties

Tanaka¹,

Okada²,

Motohashi³

et al. 2017

Materials and Contact Characterisation VIII

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Due to special characteristics of nanofibers such as nanometer sized diameter, high surface area to volume ratio and higher alignment of molecular chains, nanofibers are expected to be widely used in many applications such as filter medias, drug delivery systems and scaffolds. Nanofibers containing magnetic nanoparticles have potential uses as functional nanofibers for many applications such as sensors and materials for drug delivery systems. As a material of nanofibers, due to their biocompatible and nontoxic characteristics, polylactic acid (PLA) and magnetite (Fe3O4) can be used. In the fabrication process of nanofibers containing magnetic nanoparticles, controlling nanoparticle dispersion in nanofibers is one of the important issues to be overcome, and the effect of nanoparticle dispersion on the mechanical property of nanofibers has to be evaluated. In this study, three types of surface treatments, oleic acid treated, stearic acid treated and hot water treated are conducted to disperse magnetite in nanofibers. Random and aligned PLA nanofiber fabrics and magnetite/PLA composite nanofiber fabrics were fabricated by the electrospinning method, and their mechanical properties were revealed by tensile test. Oleic acid treatment was the most effective surface treatment. Highly aligned nanofibers can be fabricated by using a high rotation speed of drum collector. The tensile strength of PLA nanofibers and oleic acid treated magnetite/PLA composite nanofibers shows almost same values, although the other treatment has the lower tensile strength than PLA nanofibers. Aligned nanofibers tended to show high strengths.

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Structural Development of Nanoparticle Dispersion during Drying in Polymer Nanocomposite Films

Cited by 38 publications

References 47 publications

Structure Formation in Soft‐Matter Solutions Induced by Solvent Evaporation

Structure Formation in Soft‐Matter Solutions Induced by Solvent Evaporation

Particle Dispersion in Silica-Poly(vinyl alcohol) Coatings: Role of Particle-Polymer Interaction

Fabrication of Magnetite/Pla Composite Nanofiber Sheet and Evaluation of Its Mechanical Properties

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