Li, Ru-JinPezzato, CristianBerton, CesareSeverin, Kay2021-03-072021-03-072021-03-07202110.1039/D1SC00127Bhttps://infoscience.epfl.ch/handle/20.500.14299/175795Polymers containing PdnL2n complexes as network junctions were obtained by reaction of poly(ethylene glycol)-linked N-donor ligands with Pd2+. 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 Pd2+. Upon irradiation, Pd2+ 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.text::journal::journal article::research article