Construction and Applications of Well-defined Porphyrin-containing Polymers

Porphyrins and their derivatives have attracted much attention due to their unique properties and various functions, and have been widely used in energy, catalysis and biomedical fields. Porphyrin-containing polymers possess both porphyrin and polymeric characteristics, which have also aroused great interest. On the basis of functional porphyrin units, the well-defined porphyrin-containing polymers not only have a clear and specific macromolecular structure, but also have been endowed with a variety of novel and unique features. By modifying the porphyrin units into the initiators, monomers or chain transfer agents, well-defined functional porphyrin-containing polymers with specific structures could be efficiently constructed by ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain transfer (RAFT) polymerization or the combination of other strategies such as click chemistry. These well-defined porphyrin-containing polymers including telechelic polymers, alternating copolymers, block copolymers, star polymers, supramolecular polymers, can self-assemble to diverse morphologies such as spherical micelles, vesicles, nanorods and wormlike-structures and possess great potential in photodynamic therapy. Particularly, porphyrin-containing alternating copolymers can be obtained by RAFT copolymerization of 4-vinylbenzylterminated tetraphenylporphyrin and maleimide isobutyl polyhedral oligomeric silsesquioxane (POSS). The steric hindrance of POSS significantly reduces the pi-pi stacking of porphyrin units, which remarkably improve the singlet oxygen quantum yield and the photodynamic therapy efficacy.