Tailoring 2D Assemblies from Anisotropic Hexagons to Chiral Vortices by Modulating Asymmetric Side Chains in Helical Poly(phenylacetylene) Derivatives
Two-dimensional (2D) materials exhibit excellent electrical, optical, and mechanical properties, yet precise control over chiral 2D materials remains a significant challenge. This work introduces asymmetric side chain engineering to prepare helically grooved poly(3,5-disubstituted phenylacetylene)s (PPAs) and investigates the effect of their asymmetric contour on tailoring 2D nanostructures. Post-polymerization modification of a common platform polymer efficiently produced a series of rigid helical PPAs with varying alkyl side chain lengths while maintaining identical degrees of polymerization and distribution. Increasing side chain asymmetry yielded anisotropic hexagonal platelets with progressively higher aspect ratios, whereas symmetric side chains formed regular 2D hexagonal sheets. Notably, the largest side chain asymmetry generated supramolecular structures with distinct chiral vortices. Computational simulations elucidated different self-assembly mechanisms, revealing that vortex-like assemblies are kinetically stabilized rather than thermodynamically stable. All 2D assemblies exhibited significantly enhanced circularly polarized luminescence (CPL) compared to discrete polymer solutions, with dissymmetry factors (g_lum) reaching as high as 0.1. This work establishes side chain asymmetry as a crucial factor for programming supramolecular chirality and opens new avenues for developing advanced chiroptical materials.