Photoresponsive Reversible Assembly of Helical Poly(isocyanide)s

Abstract

We report the synthesis of helical poly(isocyanide)s (PICs) functionalized with azobenzene-ureidopyrimidinone (Azo-Upy) motifs, designed to provide photoswitchable control over quadruple hydrogen-bonding interactions. The PICs were accessed via nickel-catalyzed polymerization with controlled molecular weights and low dispersities. With the photoisomerization of the E-Azo-Upy motif to form the (Z-Azo-Upy)2 dimer, the resulting polymers undergo reversible hydrogen bonding triggered by UV/blue light irradiation. The assembly can be tuned between intrachain collapse and interchain cross-linking by varying concentration or solvent. Circular dichroism (CD) spectroscopy confirms that the helical integrity of the PIC backbone is retained during the photoswitching process. Furthermore, an azide-functionalized Azo-Upy motif exhibits efficient photoresponsiveness to facilitate postpolymerization modification using click chemistry. The presented system establishes a robust platform for realizing controllable assembly of helical polymers to achieve higher-order structural hierarchies through photoresponsive hydrogen bonding.