Photo-induced　controlled　radical　polymerization　(CRP)　mediated　by　heterogeneous　catalysts　provides　excellent　spatiotemporal　control　and　has　been　widely　studied　in　view　of　green　chemistry　and　potential　biomedical　applications.　In　this　paper,　an　ionic　heterogeneous　catalyst　(TD-I)　was　synthesised　in　a　facile　manner　under　mild　conditions　for　inducing　the　reversible　complexation-mediated　polymerization　(RCMP)　of　poly　(polyethylene　glycol　monomethyl　ether　methacrylate)　(PPEGMA)　in　an　aqueous　solution　under　white　LED　light　irradiation.　The　obtained　PPEGMA　has　a　controllable　molecular　weight　and　a　narrow　molecular　weight　distribution.　The　spatio-temporal　control　of　the　catalytic　system　and　the　high　chain　end　fidelity　of　the　polymer　have　been　successfully　verified　by　on-off　light　experiments　and　chain　expansion　experiments.　The　activity　and　efficiency　of　TD-I　remained　essentially　unchanged　after　being　used　for　three　cycles.　Such　a　heterogeneous　photocatalyst　which　can　be　easily　separated　and　efficiently　reused　is　promising　for　industrial　applications.　©　2022　The　Royal　Society　of　Chemistry.