Fabrication of Polyelectrolyte Sheets of Unimolecular Thickness via MOF-Templated Polymerization
Ami Nishijima, Yuki Hayashi, Koichi Mayumi, Nobuhiko Hosono, Takashi Uemura
Abstract
Two-dimensional (2D) electrolytes have intrigued researchers due to their anisotropic structures and unconventional properties. This report introduces the bottom-up synthesis of a polymer-based 2D electrolyte utilizing a metal–organic framework (MOF), [Ni(Hbtc)(bpy)] n ( 1 ), with a pillared-layer structure as a template. Crosslinking polymerization of methyl methacrylate (MMA) within MOF nanochannels comparable in size to the vinyl monomer resulted in poly(methyl methacrylate) (PMMA) monosheets. Following hydrolysis of this precursor polymer successfully gave 0.6 nm thick poly(methacrylic acid) (PMAA) sheets. Despite the crosslinked structure, the obtained polymer (PMAA- 1 ) is highly soluble as monosheets dispersed in water at a pH higher than 5.7. PMAA- 1 shows viscous liquid-like nature with the addition of the Al 3+ ion, which inherently promotes hydrogel formation of conventional linear PMAA. The topological effects of the 2D polyanion network structure on the uptake of cations in the matrix are likely responsible for these remarkable solution and viscoelastic properties of PMAA- 1 .