Metal- and halogen-free photochromic polymer films with electron transfer

Achieving metal- and halogen-free organic photochromism with rapid photoinduced coloration and reversible, thermally activated bleaching remains challenging. Here we report a photochromic film comprising 2-dibenzothienyldiphenylphosphine oxide (DBS) as the electron acceptor and a polyester ether (PGBN) as the matrix, synthesized by one-step anionic hybrid copolymerization of N,N-dimethyl-p-phenylenediamine (DMP), glycidol (GL) and 1,4-butanediol diacrylate (BDDA). Under 365 nm UV irradiation (5 W), the film reaches its fully colored state within 40 s and recovers its initial state upon thermal treatment. It also exhibits good cycling stability and can be repeatedly patterned and erased. Experimental and theoretical results show that this rapid, fully reversible response originates from photoinduced intermolecular electron transfer between the DMP donor units in PGBN and the DBS acceptor, while the polyether network modulates the photochromic behavior by effectively dispersing the donor and acceptor components. These properties enable rapid, rewritable optical information storage.