Single-crystal-to-single-crystal(SCSC) polymerizationoffers aneffective protocol for the environmentally friendly preparation ofpolymer single crystals (PSCs) with extremely high crystallinity andvery large molecular weights. Single-crystal X-ray diffraction (SCXRD)serves as a powerful technique for the in-depth characterization oftheir structures at a molecular level. Hence, a fundamental understandingof the structure-property relationships of PSCs is within ourreach. Most of the reported PSCs, however, suffer from poor solubility,a property which hampers their post-functionalization and solutionprocessability when it comes to practical applications. Here, we reportsoluble and processable PSCs with rigid polycationic backbones bytaking advantage of an ultraviolet-induced topochemical polymerizationfrom an elaborately designed monomer that results in a multitude ofphotoinduced 2 + 2 cycloadditions. The high crystallinity and excellentsolubility of the resulting polymeric crystals enable their characterizationboth in the solid state by X-ray crystallography and electron microscopyand in the solution phase by NMR spectroscopy. The topochemical polymerizationfollows first-order reaction kinetics to a first approximation. Post-functionalizationof the PSCs by anion exchange renders them super-hydrophobic materialsfor water purification. Solution processability endows PSCs with excellentgel-like rheological properties. This research represents a majorstep towards the controlled synthesis and full characterization ofsoluble single-crystalline polymers, which may find application inthe fabrication of PSCs with many different functions.
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