Anionic polymerization. VI. Effect of polar modifiers on alkylsodium and alkylpotassium polymerization of butadiene

Abstract

AbstractIt was found that N,N,N′,N′‐tetramethylethylene diamine and hexamethyl phosphorus triamide minimize chain transfer reactions in the polymerization of 1,3‐butadiene in hydrocarbon solvent with alkylsodium or alkylpotassium initiators. The polymers obtained with alkylsodium initiators had a high molecular weight and high vinyl content at 90–95% conversion. The molecular weight of the polybutadiene made by alkylsodium and alkylpotassium initiators was dependent on the polymerization temperatures and modifier ratios, but the vinyl contents were independent of the modifier ratios. Vinyl contents of alkylpotassium‐initiated polymers showed a slight dependency on polymerization temperature; the vinyl contents of alkylsodium‐initiated polymers were independent of temperature. Addition of lithium tert‐butoxide and potassium tert‐amylate to these initiators in the presence of the modifiers affected the molecular weight but not the microstructure.