Mono- and bis-functionalized copillar[5]arenes 1 and 2 form pH- and photo-responsive supramolecular polymers. Protonation of 1 enhances polymerization (1-H), differing from neutral 2, which forms a 1:1 complex with DMP5 via cavity binding. Polymerization and morphology are tunable by pH and light, as shown by NMR, UV–vis, and FE-SEM analyses.

Abstract

Mono- and bis-triazolylphenylazoaniline-functionalized copillar[5]arenes 1 and 2 were synthesized forming linear supramolecular polymers with dual pH and photo responsiveness. Upon acidification, copillar[5]arene 1 undergoes protonation, converting its aniline group into a primary ammonium ion (1-H), which significantly enhances its supramolecular polymerization compared to 1. Designed as an AB-type supramolecular polymer, 1-H exhibits distinct polymerization behavior in contrast to neutral copillar[5]arene 2, which forms a 1:1 supramolecular polymer with dimethoxypillar[5]arene (DMP5). Copillar[5]arene 2 is believed to bind DMP5 through its cavity, linking two aniline groups from separate molecules to form a two component supramolecular polymer. The degree of polymerization of 1-H and the 1:1 ratio of 2 and DMP5 can be controlled by adjusting the pH, as confirmed by pH- and concentration-dependent ¹H-NMR and diffusion-ordered spectroscopy (DOSY) experiments. UV–vis spectroscopy and FE-SEM were further used to examine the effects of photoirradiation on polymer morphology and absorption at varying concentrations.