KINETICS OF ISOPRENE POLYMERIZATION IN THE PRESENCE OF 2-ETHYLHEXYLSODIUM AND ITS MIXTURES WITH 2-ETHYLHEXYLLITHIUM IN HYDROCARBON SOLVENTS

The anionic polymerization of isoprene with 2-ethylhexylsodium soluble in hydrocarbons in the absence of electron donor additives has been s tudied. The kinetics of the propagation reaction is shown to strongly depend on the solvent used. In toluene, the reaction order in initiato r appears to be fractional, its value being dependent on the initiator concentration, while in heptane the first order is known to be follow ed. For polymerization in toluene, a scheme is suggested where monomer ic and tetrameric active species are supposed to take part in propagat ion. With a non-linear regression fit, apparent constants in the equat ion describing this scheme were evaluated. The kinetics of isoprene po lymerization with the mixed 2-ethylhexylsodium/2-ethylhexyllithium ini tiator, as well as W spectra of the living polymers obtained, were als o studied. Formation of complex active species is suggested.