Hierarchical assembly of thermoresponsive helical dendronized poly(phenylacetylene)s through photo-crosslinking of the thermal aggregates

[Display omitted] •Helical dendronized PPA homopolymers were synthesized, which showed characteristic thermoresponsive behavior and tunable helicities.•Thermally-induced assembly of these helical homopolymers was investigated, dependent on their worm-like molecular geometry and radial amphiphilicity.•Hexagonal chain packing was formed through thermal collapse of these dendronized homopolymers in water, simultaneously enhanced the supramolecular chirality.•In situ photo-crosslinking of the thermal aggregates from these dendronized homopolymers afforded hierarchical structures with high stability both in the morphologies and the memorized chiralities.•Photo-crosslinking of the thermal aggregates was happened within individual aggregates due to protection of the dendritic pendants. Supramolecular assembly of helical homopolymers to form stable chiral entities in water is highly valuable for creating chiral nanostructures and fabricating chiral biomaterials. Here we report on thermally induced supramolecular assembly of helical dendronized poly(phenylacetylene)s (PPAs) in aqueous solutions, and their in-situ photo-crosslinking at elevated temperatures to afford crosslinked nano-assemblies with hierarchical structures and stabilized helicities. These helical dendronized homopolymers carry cinnamate-cored dendritic oligoethylene glycol (OEG) pendants, which exhibit characteristic thermoresponsive behavior. Their thermal aggregation confers hexagonal packing of the polymer chains, and simultaneously resulting in enhancement of their chiralities. Assisted by radial amphiphilicity and worm-like molecular geometry, these dendronized PPAs form supramolecular twisted fibers, spheroid particles or toroids via thermal aggregation. Through UV photoirradiation above their cloud points (Tcps), cycloaddition of cinnamate moieties from the dendritic pendants promotes intermolecular crosslinking of dendronized PPA chains within the thermal aggregates, and simultaneously, the dynamic morphologies and supramolecular chirality from the dendronized PPAs through thermally induced aggregation can be fixed. In addition, photo-crosslinking can be occurred solely within individual aggregates due to the protection of densely packed dendritic OEGs. Therefore, various crosslinked assemblies from the dendronized homopolymers with tailorable morphologies and stabilized chirality are fabricated by tuning their thermally induced dynamic aggregations followed by in-situ photo-crosslinking. We