Abstract
Topochemical polymerization reactions hold the promise of producing ultra-high molecular weight crystalline polymers. However, the totality of topochemical polymerization reactions has failed to produce ultra-high molecular weight polymers that are both soluble and display variable functionality, which are restrained by the crystal-packing and reactivity requirements on their respective monomers in the solid state. Herein, we demonstrate the topochemical polymerization reaction of a family of para-azaquinodimethane compounds that undergo facile visible light and thermally initiated polymerization in the solid state, allowing for the first determination of a topochemical polymer crystal structure resolved via the cryoelectron microscopy technique of microcrystal electron diffraction. The topochemical polymerization reaction also displays excellent functional group tolerance, accommodating both solubilizing side chains and reactive groups that allow for post-polymerization functionalization. The thus-produced soluble ultra-high molecular weight polymers display superior capacitive energy storage properties. This study overcomes several synthetic and characterization challenges amongst topochemical polymerization reactions, representing a critical step toward their broader application.
Highlights
Topochemical polymerization reactions hold the promise of producing ultra-high molecular weight crystalline polymers
The AQM ditriflates in this study (Fig. 1a) employ substituted phenyl or phenolic end groups, which are homologues of the previously reported thiophene-end capped AQMs60,61
While the thienylidene AQMs are photochemically and thermally stable in the solid state, the new AQM series display remarkable solid-state reactivity that is suitable for Topochemical polymerizations (TCPs) applications
Summary
Topochemical polymerization reactions hold the promise of producing ultra-high molecular weight crystalline polymers. The totality of topochemical polymerization reactions has failed to produce ultra-high molecular weight polymers that are both soluble and display variable functionality, which are restrained by the crystal-packing and reactivity requirements on their respective monomers in the solid state. As hinted at by others previously, an alternative strategy to produce a wide variety of useful UHMW polymers from TCP reactions would be to make use of a monomeric structure that incorporates both the solubilizing sidechains and a reactive functional group that survives the TCP reaction, allowing for postpolymerization functionalization[3,23,53] If successful, this method would represent one of the few routes to soluble UHMW polymers with functionality that is not significantly restrained by the polymerization conditions[54,55,56,57]. The bestowed solution processability enables the fabrication of dielectric film capacitors that show excellent capacitive energy storage properties
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