Conjugated　polymers　are　deemed　as　conductive　carrier　mediators　for　engendering　the　pi　electrons　along　the　molecular　framework,　while　the　role　of　nonconjugated　insulated　polymers　has　been　generally　overlooked　without　the　capability　to　participate　in　the　solar-powered　oxidation-reduction　kinetics　and　charge-transfer　process.　Alternatively,　considering　the　ultrashort　charge　lifetime　and　significant　deficiency　of　metal　nanocluster　(NC)-based　photosystems,　the　fine　tuning　of　charge　migration　over　atomically　precise　ultrasmall　metal　NCs　as　novel　light-harvesting　antennas　has　so　far　not　yet　been　unleashed.　Here,　we　unlock　the　charge-transfer　capability　of　a　nonconjugated　polymer　to　modulate　the　charge　flow　over　metal　NCs　(Au-x　and　Au-25)　by　such　a　solid-state　nonconductive　polymer　via　a　conceptually　new　chemistry　strategy　by　which　l-glutathione　(GSH)-capped　gold　(Au-x@GSH)　NCs　and　poly(diallyl-dimethylammonium　chloride)　(PDDA)　were　alternately　self-assembled　on　the　metal　oxide　(MO:　WO3,　Fe2O3,　and　TiO2)　substrates.　The　ultrathin　nonconjugated　PDDA　interim　layer　periodically　intercalated　in-between　Au-x　(Au-25)　NC　layers　concurrently　serves　as　an　unexpected　charge-transfer　mediator　to　foster　the　unidirectional　electron　flow　from　Au-x(Au-25)　NCs　to　MOs　by　forming　a　tandem　charge-transfer　chain,　hence　endowing　the　multilayered　MO/(PDDA-Au-x)(n)　heterostructures　with　significantly　boosted　photoelectrochemical　water　oxidation　performance　under　light　irradiation.　The　unanticipated　role　of　PDDA　as　a　cascade　charge　mediator　is　demonstrated　to　be　universal.　Our　work　would　unlock　the　potential　charge-transport　capability　of　nonconjugated　polymers　as　a　novel　charge　mediator　for　solar-to-chemical　conversion.