CROWN-ETHER AS THE PHASE-TRANSFER CATALYST FOR FREE-RADICAL POLYMERIZATION OF HYDROPHOBIC VINYL MONOMERS

Various crown ethers were used as phase-transfer catalysts for free radical polymerizations of some water-insoluble vinyl monomers such as acrylonitrile, methylmethacrylate and styrene with persulfate as initiator. The catalytic abilities of these crown ethers for free radical polymerization of acrylonitrile with S2O82-ion as an initiator were in the order: 18-crown-6 > 15-crown-4 > 12-crown-4 > benzo- 15-crown-5 > dibenzo-18-crown-6. Among various persulfates such as Na2S2O8, K2S2O8 and (NH4)2S2O8, ammonium persulfate was the optimum initiator for the polymerization of acrylonitrile catalyzed by 18-crown-6 or 15-crown-5. Among the organic solvents used, chloroform seems to be the best solvent for the catalytic polymerization of acrylonitrile. An apparent activation energy of 72.9 kJ mol-1 was observed for the polymerization of acrylonitrile. The catalytic reaction rates of free radical polymerization for these hydrophobic vinyl monomers were in the order: acrylonitrile > methylmethacrylate > styrene > isoprene. Effects of concentrations of crown ether, initiator, and nitrogen on the polymerization of these vinyl monomers were investigated.