Polimer hidrogel mampu melakukan swelling bila menyerap air serta mampu mempertahankan medium cair di dalam jaringannya. Sintesis hidrogel kitosan-cangkok-Poli N-(vinil kaprolaktam) atau kitosan-cangkok-PNVCL dilakukan melalui polimerisasi radikal dengan teknik larutan. Kemampuan swelling hidrogel kitosan-cangkok-PNVCL dilakukan dengan merendam dalam media cair selama 24 jam. Polimer diinisiasi dengan Ammonium persulfat (APS) lalu dicangkok dengan monomer N-Vinil Kaprolaktam (NVCL) dan diikat silang dengan N,N’-Metilen Bisakrilamida (MBA). Variasi konsentrasi monomer NVCL dan konsentrasi agen pengikat silang MBA serta waktu reaksi mempengaruhi rasio swelling hidrogel. Rasio swelling paling optimum sebesar 52.8% dari berat semula didapat dengan agen pengikat silang MBA 3% dan konsentrasi NVCL 0,8 g. Hidrogel tersebut dikarakterisasi dengan Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) dan Scanning Electron Microscope (SEM).

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Hydrogel polymer will swell if it absorbs amount of water then it can protected amount of water in his network . Hydrogel chitosan-graft-poly(Vinyl Caprolactam) or chitosan-graft-PNVCL was synthesized by radical polymerization in solution. Swelling behavior of hydrogel was carried in aqueous media for 24 hour. Hydrogel was intiated by ammonium persulfate (APS) then grafted by N-Vinyl caprolactam (NVCL) and cross linked by N’N-Metilen Bisacrylamide (MBA).

Variation of monomer concentration, cross linker concentration and reaction time will effect swelling ratio hydrogel. The best swelling ratio up to 52.8% was obtained by composition of 3% MBA and 0.8 g NVCL. The products were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscope (SEM).