title: Small-angle neutron scattering study on microstructure of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) in water.
abstract: By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D2O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 degrees C in a temperature range of transparent sol below 30 degrees C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration W(p)>3.5% (w/v), corresponding to opaque gel above 30 degrees C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 degrees C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.
authors.affiliation: Graduate School of Science and Technology, Chiba University, Chiba 263-8522, Japan.
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Motokawa
authors.forename: Masahiko
authors.initials: M
authors.lastname: Annaka
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakahira
authors.forename: Satoshi
authors.initials: S
authors.lastname: Koizumi
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D009502:Neutrons; D011092:Polyethylene Glycols / Q000737:chemistry*; D012542:Scattering, Radiation; D014867:Water / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D014867:Water; C052970:poly-N-isopropylacrylamide; D011092:Polyethylene Glycols