Polyacrylonitrile (PAN) was modified by copolymerizing with methyl acrylate (MA) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS abbreviated as AP), and blended with cellulose acetate (CA) in dimethyl formamide. Scanning electron microscopy (SEM) showed much finer domain morphology for MA-PAN blends than AP-PAN blends. Dynamic mechanical property measurements showed an inward migration of the two glass transition temperatures (T-g) viz., T-g's Of PAN and CA, however the migration of PAN T-g was more pronounced in AP-PAN blends, the result agreed well with the conjugate phase calculation The phase inversion composition, calculated using Coran-Patel model agreed well with SEM morphology.