Smartly tuning supramolecular chirality in polymer gels via photoexcitation-induced cooperative self-assembly

Although supramolecular chirality tuning is prosperous in systems with small molecular building blocks, these systems lack structural strength and have limited practical applications. Conversely, polymer systems do not exhibit these drawbacks but suffer from topological chain entanglement, which often leads to large dynamic obstacles and therefore limits the tunability of supramolecular chirality. Herein, we report that by manipulating stoichiometry and employing light to alter the H-bond crosslinking between a photoexcitation-induced aggregatable molecule and high molecular weight poly(L-lactic acids), supramolecular chirality tuning of the polymer gel systems can be achieved in different ways through a cooperative self-assembly. Specifically, the Cotton effects of the examined systems can be negatively tuned by varying their stoichiometry, while positive tuning can be realized by photoirradiation. After deexcitation, negative Cotton effect tuning occurs again spontaneously in some cases. Such supramolecular chirality tuning is accompanied by rheological property tuning, demonstrating that our strategy can overcome polymer chain entanglement limitations. The proposed strategy inspires further works on the precise control of polymer chirality and, hence, development of asymmetric materials with changeable optical activity and modulus.