In the present study native cellulose acetate (CA) gel and the semi IPNs of cellulose acetate and polyacrylonitrile (CA-PAN) crosslinked with N,N'-methylene-bisacrylamide (MBA) were synthesized by redox polymerization method. The concentration of acrylonitrile (AN) was varied in the feed mixture to analyze the mechanical, structural and morphological changes in the resulting semi IPNs and compared with the native CA gel. The observed changes were investigated using Fourier Transform Infrared Microscopy (FTIR), Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD) and Thermo Gravimetric Analysis (TGA) techniques. The crosslinking of acrylonitrile (AN) in the cellulose acetate matrix by MBA to form semi IPNs was structurally analyzed by FTIR spectroscopy. By SEM and AFM analysis, it was observed that acrylonitrile played a significant role in controlling the morphological parameters like surface skewness, kurtosis and redundance of the prepared semi IPNs. X-Ray diffraction and thermo gravimetric analysis suggested an enhancement in crystallinity and thermal stability of the CA-PAN semi IPNs. Moreover, the effect of reaction variables on percent porosity and swelling ratio was investigated and optimized by adjusting the concentrations of polymer, monomer and crosslinking agent. The prepared semi IPNs were also studied for microhardness property and thus novel CA-PAN semi IPNs were synthesized with excellent mechanical, morphological, thermal and swelling properties that make them potential materials for many pharmaceutical and industrial applications in comparison to native CA gel.