DNA-tethered　poly-N-isopropylacrylamide　copolymer　chains,　pNIPAM,　that　include　nucleic　acid　tethers　have　been　synthesized.　They　are　capable　of　inducing　pH-stimulated　crosslinking　of　the　chains　by　i-motif　structures　or　to　be　bridged　by　Ag+　ions　to　form　duplexes.　The　solutions　of　pNIPAM　chains　undergo　crosslinking　at　pH　5.2　or　in　the　presence　of　Ag+　ions　to　form　hydrogels.　The　hydrogels　reveal　switchable　hydrogel-to-solution　transitions　by　the　reversible　crosslinking　of　the　chains　at　pH　5.2　and　the　separation　of　the　crosslinking　units　at　pH　7.5,　or　by　the　Ag+　ion-stimulated　crosslinking　of　the　chains　and　the　reverse　dissolution　of　the　hydrogel　by　the　cysteamine-induced　elimination　of　the　Ag+　ions.　The　DNA-crosslinked　hydrogels　are　thermosensitive　and　undergo　reversible　temperature-controlled　hydrogel-to-solid　transitions.　The　solid　pNIPAM　matrices　are　protected　against　the　OH-　or　cysteamine-stimulated　dissociation　to　the　respective　polymer　solutions.