Synthesis of Two-Dimensional Mechanically Interlocked Polymers at the Hundred-Gram Scale

Mechanical bonds impart unique mechanical properties to polymers. However, forming polymers with many mechanical bonds is traditionally difficult and has limited the study of mechanically interlocked materials (MIMs) to milligram-scale amounts and/or sparse incorporation of interlocked components. We recently introduced a two-dimensional polymer architecture in which every repeat unit contains a mechanical bond through a copolymerization reaction between crystalline and diffusible monomers. Here we described a significantly accelerated variant of this polymerization that enabled scaling to >100 g batches of the polymer and the preparation of >500 g of the polymer in total using equipment found in most academic research laboratories. This polymer is produced in a two-step procedure in which a tetrafunctional phenol monomer is crystallized into a mechanically interlocked structure supported by hydrogen bonding, after which polymerization occurs by reaction with dimethyldichlorosilane in hexanes, a nonsolvent for the crystal. Improved polymerization efficiency and kinetics were realized by incorporating triethylamine, which accelerates siloxane bond formation and incorporates into the monomer crystal in a single-crystal-to-single-crystal transformation. Crystallization procedures to produce monomer crystals in 50-g batches and polymerization techniques to produce the 2D MIM in 100-g batches are reported. TPE-PhO[Si(CH₃)₂]₂ produced at these larger scales shows consistent chemical composition by X-ray photoelectron spectroscopy and NMR spectroscopy and the expected 2D morphology by scanning electron microscopy and atomic force microscopy. These findings introduce 2D MIMs as a unique yet readily accessible polymer architecture.