Neutron spin-echo studies on crossover from single chain motion to collective dynamics

Kanaya, Toshiji; Takahashi, Nobuaki; Inoue, Rintaro*; Matsuba, Go*; Nishida, Koji*; Nagao, Michihiro*

In a previous paper we have performed neutron spin-echo (NSE) measurements on deuterated styrene (dPS)-protonated butadiene diblock copolymer micelles in deuterated n-decane to investigate the dynamics of butadiene (PB) blocks in the corona. We found that the motion of the PB chain can be well described by the Zimm mode in contrast to the previous NSE studies on dPS-protonated isoprene (PI) diblock copolymers micelles where the collective dynamics (breathing mode) of PI chains in the corona were observed. This difference has been assigned to the larger interactions in PI chains through the second virial coefficient. If this expectation is correct, crossover from the Zimm mode to the collective mode should be observed at a lower Q in PB than PI in the equal concentrations. In order to confirm the prediction, we performed NSE measurements on deuterated n-decane solutions of PB and PI with molecular weights Mw = 19.9k and 21.4k, respectively, using iNSE spectrometer at JRR-3M reactor.