Helical-Sense Matching Facilitates Supramolecular Copolymerization of Helical–Chiral Pillar5arenes

Supramolecular polymerization using two-dimensional π-conjugated chiral monomers has been mainly demonstrated because the supramolecular polymerization can be controlled by stereocommunication through π-π stacking between the two-dimensional chiral monomers. We herein report supramolecular copolymerization utilizing three-dimensional pentahedrons with twisted helical chirality through different combinations of helical-chiral acidic and basic pillar5arenes as comonomers. In this case, helical-sense matching is key to facilitating the supramolecular copolymerization. Based on the unique helical chirality of the three-dimensional pillared structure of the pillar5arenes and alternate ion-pairing interactions between acidic and basic groups on their bilateral rims, the homochiral helical-sense matching system forms kinetically stable nanowire-shaped supramolecular copolymers, generating the supramolecular gel in high concentrations. At elevated temperatures, the nanowire structure undergoes a transformation into thermodynamically stable nanoparticles, resulting in a gel-to-sol transition. This process can be hindered by introducing linear guest molecules, which prohibit the unit swing of pillar5arenes and stabilize the nanowires and supramolecular gel. By tailoring the enantiomeric ratio (e.r.) values of the chiral combinations, the helical-sense-dependent gel-to-sol transition was realized, specifically by decreasing the e.r. values. Because of helical-sense mismatching, the heterochiral system generates short, branched nanowires and presents as a turbid solution. These distinct differences reveal that the helical-sense matching between three-dimensional chiral pillar5arene comonomers is important for supramolecular copolymerization.