Solution processable liquid metal nanodroplets by surface-initiated atom transfer radical polymerization

• Published in: Nature nanotechnology Vol. 14; no. 7; pp. 684 - 690
• Main Authors: Yan, Jiajun, Malakooti, Mohammad H, Lu, Zhao, Wang, Zongyu, Kazem, Navid, Pan, Chengfeng, Bockstaller, Michael R, Majidi, Carmel, Matyjaszewski, Krzysztof
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.07.2019
• Subjects: Acrylics; Automation; Chemical industry; Chemical synthesis; Crystallization; Droplets; Elastomers; Gallium; Indium; Liquid metals; Manufacturing engineering; Metals; Optical properties; Organic solvents; Polymerization; Polymethyl methacrylate; Polymethylmethacrylate; Robotics; Solvents
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/s41565-019-0454-6

Eutectic gallium indium (EGaIn) is a liquid metal alloy at room temperature. EGaIn microdroplets can be incorporated into elastomers to fabricate highly stretchable, mechanically robust, soft multifunctional composites with high thermal stability and electrical conductivity that are suitable for applications in soft robotics and self-healing electronics . However, the current methods of preparation rely on mechanical mixing, which may lead to irregularly shaped micrometre-sized droplets and an anisotropic distribution of properties . Therefore, procedures for the stabilization of sub-micrometre-sized droplets of EGaIn and compatibilization in polymer matrices and solvents have attracted significant attention . Here we report the synthesis of EGaIn nanodroplets stabilized by polymeric ligand encapsulation. We use a surface-initiated atom transfer radical polymerization initiator to covalently functionalize the oxide layer on the surface of the EGaIn nanodroplets with poly(methyl methacrylate) (PMMA), poly(n-butyl acrylate) (PBMA), poly(2-dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(n-butyl acrylate-block-methyl methacrylate) (PBA-b-PMMA). These nanodroplets are stable in organic solvents, in water or in polymer matrices up to 50 wt% concentration, enabling direct solution-casting into flexible hybrid materials. The liquid metal can be recovered from dispersion by acid treatment. The nanodroplets show good mechanical, thermal and optical properties, with a remarkable suppression of crystallization and melting temperatures (down to -80 °C from 15 °C).