Ring-opening copolymerization of maleic anhydride with propylene oxide by double-metal cyanide

Ring-opening copolymerization of maleic anhydride (MA) with propylene oxide (PO) was successfully carried out by using double-metal cyanide (DMC) based on Zn-3[Co(CN)(6)](2). The characteristics of the copolymerization are presented and discussed in this article. The structure of the copolymer was characterized with IR and H-1-NMR. Number-average molecular weight (M-n) and molecular weight distribution (MWD) of the copolymer were measured by GPC. The results showed that DMC was a highly active catalyst for copolymerization of MA and PO, giving high yield at a low catalyst level of 80 mg/kg. The catalytic efficiency reached 10 kg polymer/g catalyst. Almost alternating copolymer was obtained when monomer charge molar ratio reached MA/PO greater than or equal to 1. The copolymerization can be also carried out in many organic solvents; it was more favorable to be carried in polar solvents such as THF and acetone than in low-polarity solvents such as diethyl ether and cyclohexane. The proper reaction temperature carried in the solvents was between 90 and 100 degreesC. The M-n was in the range of 2000-3000, and it was linear with the molar ratio of conversion monomer and DMC catalyst. The reactivity ratio of MA and PO in this reaction system was given by the extended Kelen-Tudos equation: eta = [r(1) + (r(2)/alpha)]xi - (r(2)/a) at some high monomer conversion. The value of reactivity ratio r(1)(MA) = 0 for MA cannot be polymerized itself by DMC catalyst, and r(2)(PO) = 0.286. The kinetics of the copolymerization was studied. The results indicated that the copolymerization rate is first order with respect to monomer concentration. (C) 2004 Wiley Periodicals, Inc.