Synthesis and Photo-responsive Self-Assembly of Azobenzene-Containing Molecular Brushes

Molecular brushes (MBs) are a unique type of branched macromolecules which graft polymeric chains onto a linear polymeric backbone densely. Crowded tethered side chains generate strong steric repulsion and force the backbone to stretch out, resulting in a persistent cylindrical shape and low density of entanglements of brushes. Owing to the unique rheological and mechanical properties and self-assembly behaviors, MBs show a great potential in nanotechnology and surface science. Herein, the synthesis of novel MBs of polyacrylate-g-poly(6-(4-butyl-4'-oxyazobenzene)hexylacrylate)/barbituric acid (PA-g-PAzo/Bar) was reported, in which PAzo brushes and hydrogen-bonding barbituric acid were grafted using the combination of concurrent atom transfer radical polymerization (ATRP) and click reaction. MBs-based aggregates change from cylinder to compound micelle by increasing the concentration. It is interesting that morphology transitions of cylinder-to-porous nanosheet and compound micelle-to-pearl-necklace were observed upon UV irradiation, that was ascribed to the trans-to-cis isomerization of PAzo brushes.

Automated summary

Molecular brushes (MBs) are a unique type of branched macromolecules with special rheological and mechanical properties, suitable for nanotechnology and surface science. By studying the synthesis and properties of PA-g-PAzo/Bar, it was found that the morphology of MBs-based aggregates changes from cylinder to compound micelle with increasing concentration, and transitions of cylinder-to-porous nanosheet and compound micelle-to-pearl-necklace were observed under UV irradiation, attributed to the trans-to-cis isomerization of PAzo brushes.