title: Self-assembled microspheres driven by dipole-dipole interactions: UCST-type transition in water.
abstract: A double hydrophilic block copolymer, poly(ethylene glycol)-poly(3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate) (PEG-SB), is synthesized by reversible addition-fragmentation transfer (RAFT) polymerization using PEG methyl ether (4-cyano-4-pentanoate dodecyl trithiocarbonate) as a chain transfer agent. PEG-SB forms multi-layered microspheres with dipole-dipole interactions of the SB side chains as the driving force. The PEG-SB polymers show an upper critical solution temperature (UCST) and the UCST is controllable by the polymerization degree. The PEG-SB microspheres are dissociated above the UCST and then monodispersed microspheres (∼1 μm) are obtained when the solution temperature is decreased below the UCST again. The disassociation/association of the microspheres is also controllable using the concentration of NaCl. These multi-responsive microspheres could be a powerful tool in the field of nano-biotechnology.
authors.affiliation: Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-aza Aoba, Aoba-ku, Sendai, 980-8579, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Morimoto
authors.forename: Kanna
authors.initials: K
authors.lastname: Muramatsu
authors.forename: Tetsuichi
authors.initials: T
authors.lastname: Wazawa
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Inoue
authors.forename: Makoto
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D001709:Biotechnology; D046529:Microscopy, Electron, Transmission; D008863:Microspheres; D036103:Nanotechnology; D011108:Polymers / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D011108:Polymers; D014867:Water
keywords: dipole-dipole interactions; microspheres; self-assembly; stimuli-sensitive polymers; upper critical solution temperature