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

Miyamoto, Nobuyoshi; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Hashimoto, Takeji; Koizumi, Satoshi

The living anionic polymerization processes of isoprene and styrene in benzene- initiated by -butyl lithium were studied by in-situ small-angle neutron scattering (SANS) and time-resolved molecular weight () measurement by gel permeation chromatography (GPC). In the course of the polymerization of isoprene ( = 5300 g mol), the small angle scattering increased with the reaction time . The molecular weight and its time-change, determined by GPC, is crucial to quantitatively analyze time-resolved SANS measurements; we were able to determine association number uniquely as a function of . Upon termination of the living polymerization, SANS profile greatly changed: the scattering intensity in the intermediate -region (0.2 1.0 nm) remarkably decreased, indicating disaggregation of the living ends upon the termination. Also, strong upturn in the low-q region appeared (q 0.1 nm) due to the generation of colloidal LiOH or LiO(CH), which are insoluble in benzene. Detailed data and analyses of isoprene and styrene systems will be given in the presentation.