Small-angle neutron scattering study on specific polymerization loci induced by a copolymerization of polymerizable surfactant and styrene during miniemulsion polymerization

Motokawa, Ryuhei; Taniguchi, Tatsuo*; Sasaki, Yusuke*; Enomoto, Yuto*; Murakami, Fumiyasu*; Kasuya, Masakatsu*; Kori, Michinari*; Nakahira, Takayuki*

Macromolecules, 45(23), p.9435 - 9444, 2012/11

https://doi.org/10.1021/ma301776b

Time-resolved small-angle neutron scattering study on soap-free emulsion polymerization

Motokawa, Ryuhei; Koizumi, Satoshi; Hashimoto, Takeji; Nakahira, Takayuki*; Annaka, Masahiko*

Physica B; Condensed Matter, 385-386(1), p.780 - 782, 2006/11

https://doi.org/10.1016/j.physb.2006.06.082

A soap-free emulsion polymerization method was employed in an aqueous medium in order to synthesize an amphiphilic block copolymer of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) (NE), where Poly(N-isopropylacrylamide) (PNIPA) was polymerized from the radically activated chain ends of poly(ethylene glycol) (PEG). As the polymerization proceeds, PNIPA block chains form micelle cores stabilized by PEG brush chains emanating therefrom. When this polymerization was employed at temperatures equal to or higher than 34C, radical polymerization proceeds living-likely. To elucidate origins of the living nature, we carried out time-resolved ultra-small- and small-angle neutron scattering (USANS and SANS). USANS and SANS revealed that (1) from 15 to 60C, polymerized NE forms micelle in the solution when molecular weight reaches to a critical molecular weight for micelle formation, and (2) as the temperature increases from 34C, water and monomer content in the micelle core becomes less due to a lower critical solution temperature of PNIPA. These results indicate that low diffusivity of chain end radicals, compartmentalized in the solid-like micelle core, plays an important role to lead a quasi-living polymerization behavior.

Tensile and fatigue strength of a through-wall-electron-beam-welded joint for the vacuum vessel of a fusion reactor

Suzuki, Takayuki*; Usami, Saburo*; Kimura, Takae*; Koizumi, Koichi; Nakahira, Masataka; Takahashi, Hiroyuki*

Proceedings of 55th Annual Assembly of International Institute of Welding (IIW2002), 16 Pages, 2002/06

A new type of welded joint for the outer wall and rib of a double-walled vacuum vessel of a fusion reactor has been developed. The joint is manufactured by through-wall electron-beam welding (TW-EBW), in which the beam is injected from the outside of the outer wall. Static and fatigue tests are carried out on one-bead-specimens under an axial load and two-bead-specimens under a bending load. The experimental results are analytically investigated by FEM. Although this joint is partially penetrated, the net yield strength of the bead is increased by the plastic constraint due to triaxial tensile stress in the weldment. This phenomenon reduces the mean equivalent stress on the bead cross section, and the gross strength of the joint is close to that of a full thickness welded joint. The fatigue-strength reduction factor for low-cycle fatigue life is a little larger than four. The calculated fatigue-crack growth rate in the joint is conservatively calculated by using the maximum stress intensity factor of the crack and the fatigue-crack growth rate given in ASME Code Section XI.

-ray irradiation test of instrumentation and operational amplifier for remote maintenance system of ITER

Takeda, Nobukazu; Kakudate, Satoshi; Oyake, Noriyuki; Nakahira, Masataka; Shibanuma, Kiyoshi; Idesaki, Akira; Gokan, Mayo*; Morishita, Norio; Baba, Shinji*; Okamoto, Hiroki*; et al.

no journal, , 

no abstracts in English