Effect of enthalpy of polar modifiers interaction with n-butyllithium on the reaction enthalpy, kinetics and chain microstructure during anionic polymerization of 1,3-butadiene

Abstract

The influence of interaction enthalpy (ΔHMOD/BuLi) of μ, σ, σ+μ and σ-μ complexing polar modifiers with n-butyllithium on the 1,3-butadiene anionic polymerization enthalpy (ΔHBD), polymerization reaction rate (kp) and polybutadiene microstructure was studied. It has been found that enthalpy of interaction depends on complex type, molar ratio of polar modifier to n-butyllithium (MOD/BuLi) and temperature. For the first time it has been proven that with increasing ΔHMOD/BuLi the content of 1,2 butadiene (vinyl) units in the chain increases individually for each complex type but the value of ΔHBD decreases similarly for all complexes containing σ-donor groups, exhibiting linear nature. Since ΔHMOD/BuLi controls the content of butadiene isomeric structures in the chain its value was compared with polymerization reaction rate, ranging from ∼46 to ∼5500 moL/L·min, and discussed on mechanistic level.