high fluidity of concentrated nanoparticle dispersions and its relation to Cahn wetting

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H02943
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Biological physics/Chemical physics/Soft matter physics
• Research Institution: Kyushu University
• Principal Investigator: Matsubara Hiroki 九州大学, 理学研究院, 准教授 (00372748)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: ナノフルイド / ピッカリングエマルション / 濡れ転移 / 線張力

Outline of Final Research Achievements

The nanoparticles (NPs) at liquid interfaces is currently used to promote the self-assembly of NPs into 2D structures. The structures of these particle monolayers are largely determined by contact angle. In this study, the line tension was examined by the variation in the demulsification temperature of Pickering emulsions stabilized by different sized silica NPs. As temperature approaches to the consolute point, the liquid-liquid interfacial tension approaches to zero and Pickering emulsions become unstable because the NPs desorb from the interface. For the lower consolute point of the water-2,6,lutidine mixture, Pickering emulsions with smaller silica NPs were stable at temperatures close to the consolute points, showing that the negative line tension stabilized the three-phase contact between two liquid phases and NPs. The line tension in adsorbed NP systems as discussed in this study may be exploited to control theself-assembly of NPs and achieve new nanoarchitectures.

Free Research Field

物理化学、ソフトマター

Academic Significance and Societal Importance of the Research Achievements

カーン転移が駆動力する微粒子の自己集積は、微粒子の種類によらない一般的な物理現象と考えられていたため、微粒子の粒径依存性については注意が払われてこなかった。したがって、ナノ粒子濃厚分散液が粘調化しないという事実をカーン転移との相関の中で理解する本研究には、従来の定説を修正し、新しい学理を打ち立てる学術的な意義がある。また、ナノフルイドの低粘性が従来の濡れ転移の概念から逸脱した特異例であるという視点は、本研究によりナノ粒子の界面吸着が線張力に大きな影響を受けるという結論に繋がった。これはナノフルイドの産業的なデザインを理論面から支え、新材料開発にもつながることが予想される点で応用面でも意義深い。