Luminescent Boron Quinolate Block Copolymers via RAFT Polymerization

Abstract

The preparation of well-defined luminescent organoboron quinolate block copolymers via sequential RAFT polymerization is reported. Boron-containing block copolymers with PS, P­(St-<i>alt</i>-MAh), and PNIPAM as the second block were successfully synthesized. The photophysical properties of the block copolymers were studied by UV–vis and fluorescence spectroscopy. Independent of the second block, the boron quinolate block copolymers that contain the parent 8-hydroxyquinolato ligand (PM1-<i>b</i>-PS, PM1-<i>b</i>-PNIPAM, PM1-<i>b</i>-P­(St-<i>alt</i>-MAh)) are green luminescent, whereas a polymer with 5-(4-dimethylaminophenyl)-8-hydroxyquinolate as the ligand (PM2-<i>b</i>-PS) shows red luminescence. The P­(St-<i>alt</i>-MAh)-based block copolymer was further modified with photoactive azobenzene groups. The self-assembly behavior of the amphiphilic block copolymers was studied by transmission electron microscopy (TEM) and dynamic light scattering (DLS). In water, PM1-<i>b</i>-PNIPAM forms spherical micelles. The azobenzene-modified P­(St-<i>alt</i>-AbMA)-<i>b</i>-PM1 exhibits a solvent-dependent self-assembly behavior in basic solutions, and large spindle-shaped aggregates and spherical micelles were observed