Aggregation behavior of polyisoprene chain ends during living anionic polymerization as investigated by time-resolved small-angle neutron scattering

Ionic aggregation of polymer chain ends formed during living anionic polymerization of isoprene, which was initiated by sec-butyllithium in deuterated non-polar solvent (benzene- d₆), was investigated by in situ and real-time small-angle neutron scattering (SANS) and by a complementary method of gel-permeation chromatography (GPC). As the polymerization proceeded, the small-angle scattering in a Lorentzian shape emerged; its scattering intensity and apparent correlation length increased with time. The time-evolution of d Σ/d Ω( q) was analyzed on the basis of an ideal model of isolated star-polymer. Number of chains comprised of the starpolymer, f, which represents the aggregation number for the living polyisoprene, was evaluated equal to f=3.6 at the end of polymerization.