(158d) Chemical Synthesis and Physical Properties of Graphimine - a New 2D High-Performance Polymer

Graphimine is a member of a new class of two-dimensional polymers composed of hexa-substituted benzene nodes within a two-dimensional covalent organic framework (2D COF). Drawing inspiration from robust materials like graphene, graphimine comprises a rigid, aromatic network with short linkages between benzene nodes, thus having the potential to revolutionize the current standards for lightweight, high-performance materials. Graphimine is synthesized in solution from a novel hexa-substituted monomer, 2,4,6-triaminobenzene-1,3,5-tricarbaldehyde (TABTCA). TABTCA was derived from a high yielding, three-step, synthetic pathway, utilizing a substitution reaction with anhydrous ammonia and 2,4,6-tribromobenzene-1,3,5-tricarbaldehyde. Nuclear magnetic resonance spectroscopy was used to successfully confirm its chemical structure, and mass spectrometry verified its molecular weight. Polymerization of TABTCA into graphimine is conducted using reversible, acid-catalyzed polycondensation, that results in imine linkage formation, and structural re-organization via transimination to achieve the 2D COF. Graphimine is analyzed with FTIR, to determine conversion of aldehyde and amine functionalities to imine-linkages; PXRD, to analyze the resulting crystalline structure; and HRTEM, to examine interlayer stacking structure. Furthermore, graphimine has been oxidized to graphamide, which is a dense 2D polyaramid. Graphimine and graphamide are fabricated into films using techniques such as drop casting, spin-coating, and doctor blading, for applications that require extended sheets or films. These results provide evidence for the first successful production of a highly compacted imine- and amide- linked two-dimensional polymers and hold great potential for development as a new low-weight, high-strength, performance materials.