Kinetics of Jammed Systems: PNIPA Gels

László, Krisztina; Fluerasu, Andrei; Moussaı̈d, A.; Geissler, Erik

doi:10.1002/masy.201000114

Cited by 2 publications

(1 citation statement)

References 18 publications

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“…X-ray photocorrelation spectroscopy has been employed to determine the dynamics of hydrated PNiPAAm gels at temperatures above the LCST of the material. The results obtained show hyper-diffusive dynamics of PNiPAAm gels and support the notion that the ultraslow deswelling rate observed at the volume phase transition in PNIPAAm hydrogels is the result of jamming 5 . This phenomenon is intrinsic to the polymer structure and is not attributable to its hydrophobic character in the high temperature regime.…”

Section: Introductionsupporting

confidence: 82%

Deswelling of Poly(N-isopropylacrylamide) Derived Hydrogels and Their Nanocomposites with Iron Oxide Nanoparticles As Revealed by X-ray Photon Correlation Spectroscopy

et al. 2015

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Here we present results on the deswelling behavior of semiinterpenetrating polymer hydrogels of sodium alginate and poly (N-isopropylacrylamide) (PNIPAAm) containing iron oxide nanoparticles by means of X-ray photocorrelation spectroscopy (XPCS). The experiments were carried out as a function of temperature starting from temperatures below the low critical solution temperature (LCST) of the materials to temperatures above their LCST. The hydrogels present a hyper-diffusive dynamics of similar nature as that found for the freeze-dried aerogels which has been attributed to the characteristic porous structure. The dynamics of the swollen samples is faster than that of the freezedried ones suggesting that water has an effect in accelerating the dynamics of the hydrogels. XPCS has been used to characterize the deswelling process as a function of temperature. Deswelling times for the different samples correlate well with the corresponding relaxation times of the relaxation processes measured by XPCS.

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Section: Introductionsupporting

confidence: 82%

Deswelling of Poly(N-isopropylacrylamide) Derived Hydrogels and Their Nanocomposites with Iron Oxide Nanoparticles As Revealed by X-ray Photon Correlation Spectroscopy

et al. 2015

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Anomalous Dynamics of Concentrated Silica-PNIPAm Nanogels

Frenzel

Lehmkühler

Lokteva

et al. 2019

J. Phys. Chem. Lett.

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We present the structure and dynamics of highly concentrated core–shell nanoparticles composed of a silica core and a poly(N-isoproylacrylamide) (PNIPAm) shell suspended in water. With X-ray photon correlation spectroscopy, we are able to follow dynamical changes over the volume phase transition of PNIPAm at LCST = 32 °C. On raising the temperature beyond LCST, the structural relaxation times continue to decrease. The effect is accompanied by a transition from stretched to compressed exponential shape of the intensity autocorrelation function. Upon further heating, we find a sudden slowing down for the particles in their collapsed state. The q dependence of the relaxation time shows an anomalous change from τc ∝ q –3 to τc ∝ q –1. Small angle X-ray scattering data evidence a temperature-induced transition from repulsive to attractive forces. Our results indicate a temperature-induced phase transition from a colloidal liquid with polymer-driven dynamics toward a colloidal gel.

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Kinetics of Jammed Systems: PNIPA Gels

Cited by 2 publications

References 18 publications

Deswelling of Poly(N-isopropylacrylamide) Derived Hydrogels and Their Nanocomposites with Iron Oxide Nanoparticles As Revealed by X-ray Photon Correlation Spectroscopy

Deswelling of Poly(N-isopropylacrylamide) Derived Hydrogels and Their Nanocomposites with Iron Oxide Nanoparticles As Revealed by X-ray Photon Correlation Spectroscopy

Anomalous Dynamics of Concentrated Silica-PNIPAm Nanogels

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