Light-induced assembly and disassembly of polymers with Pd(n)L(2n)-type network junctions

Polymers containing Pd(n)L(2n) complexes as network junctions were obtained by reaction of poly(ethylene glycol)-linked N-donor ligands with Pd(2+). The addition of a metastable state photoacid renders the networks light sensitive, and gel–sol transitions can be achieved by irradiation with light. The inverse process, a light-induced sol–gel transition, was realized by using a molecularly defined Pd complex as an acid-sensitive reservoir for Pd(2+). Upon irradiation, Pd(2+) ions are released, allowing the formation of an acid-resistant polymer network. Both the gel–sol and the sol–gel transitions are reversed in the dark.