Despite rapid progress in recent years, it has remained challenging to prepare crystalline two-dimensional polymers. Here, we report the controlled synthesis of few-layer two-dimensional polyimide crystals on the surface of water through reaction between amine and anhydride monomers, assisted by surfactant monolayers. We obtained polymers with high crystallinity, thickness of ~2 nm and an average crystal domain size of ~3.5 μm2. The molecular structure of the materials, their grain boundaries and their edge structures were characterized using X-ray scattering and transmission electron microscopy techniques. These characterizations were supported by computations. The formation of crystalline polymers is attributed to the pre-organization of monomers at the water–surfactant interface. The surfactant, depending on its polar head, promoted the arrangement of the monomers—and in turn their polymerization—either horizontally or vertically with respect to the water surface. The latter was observed with a surfactant bearing a carboxylic acid group, which anchored amine monomers vertically through a condensation reaction. In both instances, micrometre-sized, few-layer two-dimensional polyamide crystals were grown.
Bibliographical noteFunding Information:
We acknowledge financial support from the ERC Grant on T2DCP and the EU Graphene Flagship, COORNET (SPP 1928), CONJUGATION-706082 as well as the German Science Council, Centre of Advancing Electronics Dresden, EXC1056 (Center for Advancing Electronics Dresden) and OR 349/1. H.Q. and U.K. acknowledge financial support from the DFG in the framework of the ‘SALVE’ (Sub-Angstrom Low-voltage Electron Microscopy) project as well the Ministry of Science, Research and the Arts (MWK) of Baden-Wuerttemberg in the framework of the SALVE project. K.L. acknowledges the China Scholarship Council (CSC) for financial support. We acknowledge P. Formánek for assistance with TEM, M. Löffler for scanning electron microscopy and J. Michl for helpful discussions. GIWAXS was carried out at DESY, a member of the Helmholtz Association (HGF), and at Helmholtz-Zentrum Berlin (HZB). We thank M. Schwartzkopf for assistance at the P03-MINAXS beamline and D. Többens at the KMC-2 beamline. We thank HGF and HZB for the allocation of neutron/synchrotron radiation beam time.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)