Study of the polymerization of styrene on exposure to n-butyl lithium in aromatic solvents as the first stage of the synthesis of thermoelastoplasts

Abstract

UV spectroscopy has been employed to investigate the kinetics of polymerization of styrene and isoprene and also chain transfer to the solvent at different stages of the synthesis of the thermoelastoplast styrene-isoprene-styrene in toluene and xylene on exposure to n-butyl lithium ( n-BuLi) at 20–50°C. It is shown that the introduction of the second monomer must be made immediately at the end of the first stage of synthesis to avoid deterioration of the properties of the final product because of chain transfer to the solvent. Triple copolymers have been obtained with narrow MMD having a strength at rupture 16–19 MPa and relative elongation 1100–1200%. It was found that the rate constant of initiation of polymerization of styrene in toluene is almost twice that in benzene so that on synthesis of PS forming the first block unlike the processes in benzene and aliphatic solvents all the n-BuLi has time to enter the reaction. This opens the way to the use in the synthesis of thermoelastoplasts of n-BuLi instead of sec-BuLi although the fairly wide MMD of the first block ( M w barM n = 1.25–1.5 ) may be the cause of the worsening of the properties of the material.