The copolymerization of oxetane with glutaric anhydride was found to proceed with bulky titanium bisphenolate (1) as the initiator. The H-1 NMR spectrum of the produced copolymer shows that the copolymer contains both alternating units and oxytrimethylene units in the polymer main chain. 1 was also effective for the copolymerization of oxetane with other cyclic acid anhydrides, affording the corresponding copolymers. With the titanium bisalkolate complex (4), a copolymer rich in alternating sequences was obtained.