Sintesis dan karakterisasi Hidrogel Kitosan Poli-N, N Dimetil Akril Amida (Poli NNDMAA) dengan Metode Semi-Interpenetrating Polymer Network (Semi-IPN) = Synthesis and characterization of Chitosan Hydrogel Poly - N, N Dimethyl acryl Amide (Poly NNDMAA) with semi method Interpenetrating Polymer Network (Semi-IPN)