Radical copolymerization of isobutyl vinyl ether (IBVE) with maleic anhydride (MA) gave 1:1 alternating copolymer in a wide range of monomer composition. IBVE and MA formed a 1:1 donor-acceptor complex which showed an absorption maximum at 273 nm in CHCl3. The equilibrium constant of the complexation was measured to be 0.052 M−1in CCl4at 37°C by NMR, 0.036 M−1in CDCl3at 37°C by NMR, and 0.033 M−1in CHCl3at 23°C by UV. The dilatometrically measured rate of copolymerization in CHCl3at 50°C was a maximum at a feed MA mole fraction of 0.350, 0.405, and 0.435 when the total monomer concentration was 0.5, 1, and 1.5 M, respectively. The Georgiev-Zubov method, based on the reactions of free monomers and the complex, was applied to obtain α = 0.210, β1= 65.6, and β2= 4.42.