Self‐Flocculating/Self‐Dispersing Oscillation of Microgels

Suzuki, Daisuke; Sakai, Takamasa; Yoshida, Ryo

doi:10.1002/anie.200703953

Cited by 121 publications

(137 citation statements)

References 43 publications

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“…This was mainly due to the difference in microgel concentrations (0.0001 wt % for the DLS study and 0.2 wt % for the oscillation study); we have previously confirmed that microgel concentration significantly affects the state of microgel flocculation. 19 Based on the above-mentioned results for DLS and SAXS, we were able to understand the changes in internal microscopic structures of the NRu microgels during the swelling/deswelling or dispersing/flocculating oscillations. Here, we focused on the relationship between hydrodynamic diameter (D h ) ( Figure 2b) and ξ (Figure 6) of the NRu microgels as a function of temperature.…”

Section: ■ Discussionmentioning

confidence: 99%

“…In addition, due to colloidal instability when thermoresponsive microgels are deswollen under high ionic strength (here, the BZ reaction proceeds only under high ionic strength, typically greater than 0.3 M 21 ), the microgels showed dispersing/flocculating oscillation within a narrow temperature range near critical flocculation temperature. 19,20 From this, we demonstrated that the microgels could be used as constituents of self-beating micropumps. 25 Other than their use as micro-oscillators, more recently it has been reported that Ru(bpy) 3 complex copolymerized pNIPAm microgels can also be used for enhancement of electrogenerated chemiluminescence 28 or may lead to the realization of artificial photosynthetic systems.…”

Section: ■ Introductionmentioning

confidence: 95%

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Small-Angle X-ray Scattering Study on Internal Microscopic Structures of Poly(N-isopropylacrylamide-co-tris(2,2′-bipyridyl))ruthenium(II) Complex Microgels

Matsui¹,

Kureha²,

Nagase³

et al. 2015

Langmuir

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Internal microscopic structures of poly(N-isopropylacrylamide-co-tris(2,2'-bipyridyl))ruthenium(II) complex microgels were investigated using small-angle X-ray scattering (SAXS) in the extended q-range of 0.07 ≤ q/nm(-1) ≤ 20. The microgels were prepared by aqueous free-radical precipitation polymerization, resulting in formation of monodispersed, submicrometer-sized microgels, which was confirmed by transmission electron microscopy and dynamic light scattering. To reveal the changes in the microscopic structures of the microgels during swelling/deswelling or dispersing/flocculating oscillation, the redox state of Ru(bpy)3 complexes was fixed in the microgels using Ce(IV) or Ce(III) ions under high ionic strength (1.5 M) during the SAXS measurements. The scattering intensity of the microgels manifested five different structural features. In particular, the correlation length (ξ), which was obtained from the fitting analysis using the Ornstein-Zernike equation, of the microgels both in the reduced and oxidized Ru(bpy)3 states exhibited divergent-like behavior. In addition, a low-q peak centered at q ≈ 5 nm(-1) did not appear clearly in both the reduced [Ru(bpy)3](2+) and oxidized [Ru(bpy)3](3+) states, indicating that the formation of a polymer-rich domain was suppressed; thus, Ru(bpy)3 complexes can be active even though the microgels are deswollen or flocculated during the oscillation reaction.

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Section: ■ Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 95%

Small-Angle X-ray Scattering Study on Internal Microscopic Structures of Poly(N-isopropylacrylamide-co-tris(2,2′-bipyridyl))ruthenium(II) Complex Microgels

Matsui¹,

Kureha²,

Nagase³

et al. 2015

Langmuir

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“…In addition to analyzing the polymer solutions, we prepared submicron-sized poly(NIPAAm-co-Ru(bpy) 3 ) gel beads by surfactant-free aqueous precipitation polymerization, and analyzed the oscillating behavior of the microgel dispersions [20][21][22][23][24]. At low temperatures (20-26.5 • C), on raising the temperature, the amplitude of the oscillation became larger.…”

Section: Self-oscillating Polymer Solution and Microgel Dispersion Asmentioning

confidence: 99%

Biomimetic Self‐Oscillating Polymer Gels

Yoshida¹

2013

Intelligent Stimuli‐Responsive Materials

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There have been many studies on stimuli-responsive polymer gels that exhibit a reversible swelling-deswelling change in response to environmental changes such as solvent composition, temperature, and pH change. In contrast, we have developed a novel "self-oscillating" polymer gel that exhibits autonomous mechanical oscillation without an external control in a completely closed solution ( Fig. 11.1). For the design of the gel, the Belousov-Zhabotinsky (BZ) reaction, which is wellknown for exhibiting temporal and spatiotemporal oscillating phenomena [1, 2], was focused. We attempted to convert the chemical oscillation of the BZ reaction into a mechanical change in gels and generate an autonomous swelling-deswelling oscillation under non-oscillatory outer conditions. A copolymer gel consisting of N-isopropylacrylamide (NIPAAm) and ruthenium tris(2,2 -bipyridine) (Ru(bpy) 3 ), acting as a catalyst for the BZ reaction, was prepared ( Fig. 11.2a). When the poly(NIPAAm-co-Ru(bpy) 3 ) gel is immersed in the catalyst-free BZ solution, the reaction occurs in the gel by the catalytic function of the polymerized Ru(bpy) 3 (Fig. 11.2c). The redox changes of the polymerized catalyst moiety (Ru(bpy) 3 2+ Ru(bpy) 3 3+ ) change the volume phase transition temperature as well as the swelling ratio of the gel because the hydrophilicity of the polymer chains increases at the oxidized Ru(III) state and decreases at the reduced Ru(II) state (Fig. 11.2b). As a result, the gel exhibits an autonomous swelling-deswelling oscillation with the redox oscillation in the closed solution under constant condition (Fig. 11.2d).

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“…We then prepared submicron-sized poly(NIPAAm-co-Ru(bpy) 2+ 3 ) gel beads by surfactant-free aqueous precipitation polymerization, and analyzed their oscillating behaviors [34][35][36][37]. for the microgel dispersions.…”

Section: Self-flocculating/dispersing Oscillation Of Microgelsmentioning

confidence: 99%