Systematic　study　of　FTIR　spectra　was　carried　out　on　the　PES/PVP　blends　and　PES-g-PVP　copolymers.　In　the　blends,　no　shift　of　carbonyl　group　absorbance　was　observed.　In　the　copolymers,　there　was　an　occurrence　of　blue-shift　that　increases　with　the　grafting　degree,　which　can　be　used　as　a　compelling　evidence　of　PVP　being　grafted　onto　PES.　This　phenomenon　was　interpreted　from　the　stereo-hindrance　effect.　Besides,　as　the　intensity　of　carbonyl　group　absorbance　increased　proportionally　with　the　degree　of　grafting　obtained　by　elementary　analysis,　FTIR,　a　simple　and　easy　tool,　became　feasible　for　the　quantitative　determination　of　PVP　content　in　the　graft　copolymers.　Calibration　curves　with　high　correlation　coefficient　were　established　from　which　the　quantitative　relationship　between　the　intensity　of　carbonyl　group　absorbance　normalized　by　a　chosen　internal　reference　and　the　grafting　degree　can　be　obtained.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.