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Miyamoto, Nobuyoshi; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Hashimoto, Takeji; Koizumi, Satoshi
Physica B; Condensed Matter, 385-386(1), p.752 - 755, 2006/11
Times Cited Count：5 Percentile：27.18(Physics, Condensed Matter)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(C
H
), which are insoluble in benzene. Detailed data and analyses of isoprene and styrene systems will be given in the presentation.
Tanaka, Hirokazu; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Hashimoto, Takeji
Physica B; Condensed Matter, 385-386(1), p.742 - 744, 2006/11
Times Cited Count：22 Percentile：66.99(Physics, Condensed Matter)Polystyrene-block-polyisoprene were synthesized via living anionic polymerization. We have performed in-situ and real-time SANS, GPC, and UV-vis spectroscopy of the polymerization process in order to reveal the structure formation process of the block copolymers, especially the associated structures. From GPC and UV-vs spectroscopy. It is found that isoprene monomers are preferentially polymerized, and after that, styrene monomers are to be polymerized. It is also found from SANS measurements, that living polymers in the reaction solution formed the associated structures during the polymerization process. Moerover, it is also strongly suggested that in the earlier stage of polymerization, living polymers are mainly composed of polyisoprene with association number of 4, and once styrene monomers are polymerized, the association number drastically begins to decrease from 4 to 2.
-polystyreneYamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Hashimoto, Takeji; Tanaka, Hirokazu; Motokawa, Ryuhei; Koizumi, Satoshi
Macromolecules, 39(13), p.4531 - 4539, 2006/06
Times Cited Count：36 Percentile：70.32(Polymer Science)no abstracts in English
Miyamoto, Nobuyoshi; Tanaka, Hirokazu*; Yamauchi, Kazuhiro*; Hasegawa, Hirokazu*; Hashimoto, Takeji; Koizumi, Satoshi
no journal, ,
The living anionic polymerization processes of polyisoprene, polystyrene, and polystyrene-block-polyisoprene were studied by in-situ small-angle neutron scattering (SANS) in combination with gel permeation chromatography and uv-visible spectroscopy. The polymerization reactions were carried out in benzene-d6 with sec-butyllithium as the initiator. The SANS intensity largely decreased upon termination of the living ends, indicating the presence of ionic aggregates during polymerization. The time-courses of the aggregation number f in the aggregates during the polymerizations were quantitatively estimated by analyzing the time-resolved SANS data on the basis of the model of star-polymer. In isoprene systems, the aggregation number decreased from ca. 10 to 4 with increasing molecular weight.
