A　novel　thermally　responsive　hydrogel　(TRH)　has　been　demonstrated　by　confining　poly(ethylene　oxide),　poly(propylene　oxide),　and　poly(ethylene　oxide)　triblock-copolymer　(EPE)　molecules　into　the　pores　of　polymer　framework.　Aqueous　EPE　copolymer　molecule　had　a　tendency　to　aggregate　to　form　clusters　gradually　and　precipitated　from　water　when　the　temperature　is　above　a　cloudy　point.　By　adding　EPE　molecules　into　the　acrylamide　(AM)　monomer　solution,　the　mixture　can　be　fabricated　as　uniform　and　transparent　hydrogel　via　controlled　radical　polymerization.　The　polyacrylamide　hydrogel　is　produced　with　a　switchable　optical　property　when　subjecting　to　temperature　variation.　Such　reversible　thermally　responsive　material　can　be　utilized　as　a　functional　material　for　smart　window　application.　Additionally,　the　thermal　responsive　hydrogel　is　an　inexpensive　material,　which　is　readily　applicable　as　smart　windows　with　significant　reduction　in　material　cost.