Soap-free emulsion polymerization of poly(ethylene glycol)--poly(-isopropylacrylamide); Elucidation of specific reaction fields for quasi-living polymerization by time-resolved SANS

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

Macromolecules, 43(2), p.752 - 764, 2010/01

https://doi.org/10.1021/ma9020533

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.

Frozen concentration fluctuations of a poly(N-isopropyl acrylamide) gel decomposed by neutron spin echo

Koizumi, Satoshi; Monkenbusch, M.*; Richter, D.*; Schwahn, D.*; Annaka, Masahiko*

Journal of the Physical Society of Japan, Vol.70, Supplement A, p.320 - 322, 2001/05

no abstracts in English