Using self-assembly to prepare multifunctional diblock copolymers containing azopyridine moiety

Diblock copolymers composed of polystyrene (PS) and a polymethacrylate containing an azopyridine side group (PAzPy) were synthesized using atom transfer radical polymerization for the first time. While conserving the photoactivity related to the trans-cis photoisomerization of azo dyes, the azopyridine moiety made possible the easy use of self-assembly to add new functionalities to the PAzPy block, leading to multifunctional diblock copolymers. On one hand, three carboxylic acids (one aliphatic, one aromatic, and one chiral acid) were complexed with azopyridine moieties through hydrogen bonding which transformed the amorphous PAzPy block into a liquid crystalline (LC) block. Self-assembly-induced LC phases, dependent on the nature of the acid used, could enhance the photoinduced orientation of azopyridine moieties. On the other hand, zinc-tetraphenylporphyrin (ZnTPP) was linked to azopyridine through coordination interaction between the metal and pyridyl group, showing effective loading of metal-porphyrine inside microdomains of the PAzPy block. The complexation with ZnTPP made the PAzPy block become both photoactive and electroactive. This work demonstrates the interest of the strategy of exploiting self-assembly through the use of azopyridine-containing block copolymers.