title: Spontaneous phase transfer of thermosensitive hairy particles between water and an ionic liquid.
abstract: This article describes the temperature-induced phase transfer behavior of a series of thermosensitive polymer brush-grafted particles between water and a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]). Six samples were made by surface-initiated atom transfer radical polymerization: silica particles grafted with poly(methoxypoly(ethylene glycol) methacrylate) (PPEGMMA) with two different molecular weights, poly(methoxytri(ethylene glycol) methacrylate) (PTEGMMA), poly(methoxydi(ethylene glycol) methacrylate) (PDEGMMA), and two copolymers of PEGMMA and TEGMMA with different compositions (P(PEGMMA-co-TEGMMA)-82 and P(PEGMMA-co-TEGMMA)-74). The cloud points of free PPEGMMA with M(n,SEC) of 23 and 40 kDa, P(PEGMMA-co-TEGMMA)-82, P(PEGMMA-co-TEGMMA)-74, and PTEGMMA in [EMIM][TFSI]-saturated water were 95, 94, 80, 72, and 43 °C, respectively. PDEGMMA was not soluble in the ionic liquid-saturated water. PPEGMMA brush-grafted particles moved spontaneously and completely from water to the [EMIM][TFSI] phase upon heating at 80 °C. When cooled to 22 °C, all particles returned to the water layer. From UV-vis absorbance measurements, the transfer temperature (T(tr)) of PPEGMMA-grafted particles from water to the ionic liquid was 42 °C. Thermodynamic analysis showed that the particle transfer was an entropically driven process. P(PEGMMA-co-TEGMMA)-82, P(PEGMMA-co-TEGMMA)-74, and PTEGMMA brush-grafted particles also underwent reversible and quantitative transfer between the two phases upon heating at 70 °C and cooling at 0 °C; their transfer temperatures from water to [EMIM][TFSI] were 36, 30, and 16 °C, respectively. T(tr) was a linear function of the cloud point of the corresponding free polymer in ionic liquid-saturated water. In contrast, PDEGMMA-grafted particles moved spontaneously to the ionic liquid layer upon heating but did not return to water even after prolonged stirring at 0 °C.
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Horton
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Bai
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Jiang
authors.forename: Dejin
authors.initials: D
authors.lastname: Li
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Lodge
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
mesh_terms: D002384:Catalysis; D006358:Hot Temperature; D007093:Imidazoles / Q000737:chemistry*; D007094:Imides / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: C506652:1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; D007093:Imidazoles; D007094:Imides; D052578:Ionic Liquids; D011108:Polymers; D014867:Water; D012822:Silicon Dioxide