Anionic polymerization. IV. Effect of crown ethers on alkylsodium initiator

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Abstract
The polymerization of butadiene and copolymerization of butadiene‐styrene with alkylsodium catalyst modified by crown ethers in hydrocarbon solvent has been investigated. This catalyst system produced polybutadiene of high viscosity (2.0–5.0) and high vinyl content (80%) in high conversion (75–95%). These results are in contrast to those obtained with aliphatic ether‐modified alkylsodium polymerization which typically gives products of low molecular weight and at low conversion. The copolymerization of butadiene‐styrene with alkylsodium catalyst modified by crown ethers gave a copolymer which did not contain block styrene. Although the copolymer did not contain block styrene, there was an unusually high level of incorporation of styrene in the copolymer at low conversion. This behavior is quite different from either modified organolithium or unmodified organosodium initiators, in which the styrene is uniformly and randomly incorporated along the chain.