Postpolymerization Modification-Induced Chiral Self-Assembly of Substituted Poly(phenylacetylene)s Based on <i>Cis</i>–<i>Transoid</i> to <i>Cis</i>–<i>Cisoid</i> Helical Transition
Sheng Wang, Xiaoqian Sun, Hua Zeng, Siyu Xie, Jie Zhang, Xinhua Wan
Abstract
Herein, we developed a novel postpolymerization modification-induced self-assembly (PPMISA) by subtly combining conformational transition-induced self-assembly with an activated ester-amine reaction. During the reaction, the poly(phenylacetylene) (PPA) backbone can spontaneously transform from cis–transiod to cis–cisoid helix, which reduces solubility and thus triggers in situ self-assembly, accompanied by naked-eye solution color change and turn-on fluorescence. During PPMISA, the self-assembly structures can gradually evolve from slender fibers to twisted suprahelical strands, the screw sense of which is strictly correlated with the helicity of the polyene backbone. The morphology and chemical structure of substituted PPA during PPMISA can be readily tuned by varying solvent, reaction time, and the variety of organic amines. Compared with inefficient conventional dilute solution self-assembly, these assemblies can be efficiently prepared at high solid concentrations (10 wt %) and maintain their morphologies using PPMISA at mild reaction conditions. Moreover, the obtained assemblies present strong circularly polarized luminescence with a high dissymmetry factor up to the order of 1 × 10 –2 . This PPMISA strategy may open a new avenue to efficiently fabricate structurally diverse functional nanomaterials.