Glass-liquid transition of water and ethylene glycol solution in poly(2-hydroxyethyl methacrylate) hydrogel

Hofer, Klaus; Mayer, Erwin; Johari, G. P.

doi:10.1021/j100369a083

Cited by 98 publications

(92 citation statements)

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“…These are heavily hydrated hydrophilic polymers e.g., polyhydroxy ethyl-methacrylate. In the thermal studies of such media by Hofer et al [51], a glass transition temperature of 162 K was observed, independent of the water content over a considerable range of water contents. When freezing of the water was induced by thermal cycles in these systems, the glass transition at 162 K disappears from the thermal analysis traces.…”

Section: Discussionmentioning

confidence: 94%

“…In the experiments reported in Ref. [51], the activation energy for the thermal relaxation lies in the range 80 -120 kJ=mol and a more detailed study of the relaxation that included annealing studies analyzed by the Tool-NarayanaswamyMoynihan phenomenological model [52], gave best ÿts to the data when an activation energy between the two above was used. These values are comparable with the slope in Fig.…”

Section: Discussionmentioning

confidence: 99%

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Prediction of entropy and dynamic properties of water below the homogeneous nucleation temperature

Starr

Angell

Stanley

2003

Physica A: Statistical Mechanics and its Applications

128

154

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Prediction of entropy and dynamic properties of water below the homogeneous nucleation temperature

Starr

Angell

Stanley

2003

Physica A: Statistical Mechanics and its Applications

128

154

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“…Hofer et al 39 reported that a reversible glassliquid transition should be resolved in two endotherm steps at Ϸ 132 K and Ϸ 162 K for hydrogels of poly(2-hydroxyethyl methacrylate). They attributed these endotherm peaks, supported by dielectric and conductivity studies, to transitions involving nonfreezing and freezable water fractions, respectively.…”

Section: Thermal Transitions Of Pva Hydrogelsmentioning

confidence: 99%

“…Explanations for this complex behavior are very controversial. Hofer et al 39 pointed out that the state of liquid water in the hydrogel is stable against crystallization at 230 -240 K, and this temperature depends on the water content. Dielectric relaxation studies 36 also show that this crystallization process occurs in a wide temperature range and water molecules coexist with ice at temperatures of 217-267 K. Hatakeyama et al 11 determined that the ice melting peaks are displaced to lower temperatures (Х 250 K) when the degree of reticulation increases in several crosslinking densities of PVA hydrogels.…”

Section: Thermal Transitions Of Pva Hydrogelsmentioning

confidence: 99%

Thermal transitions of poly(vinyl alcohol) hydrogel sensed by a fluorescent probe

Dibbern-Brunelli

Atvars²

2000

J. Appl. Polym. Sci.

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ABSTRACT:Fluorescence from the fluorescein molecule has been used to study of phase transition processes in five poly(vinyl alcohol) (PVA) hydrogels in the temperature range 75-350 K. These hydrogels were prepared with PVA with molecular weight ϭ 124,000 -186,000, 99ϩ% hydrolyzed, by repeated freezing-thawing cycles in five compositions: 9.9, 11.1, 13.3, 16.5, and 20.9 PVA w/w %. Plots of total fluorescence intensity versus temperature, normalized with the fluorescence signal at 75 K, and of the emission wavelength maximum versus temperature indicated that the dynamic of the guest deactivation was dependent on the hydrogel thermal transitions. These thermal transition processes were compared to three model systems: uranine (fluorescein di-sodium salt) in water, fluorescein in water/ethanol (85%/15% v/v), and fluorescein/PVA homopolymer. Small spectral shifts were obtained for these model systems over the entire temperature range attributed to the hot band effect. Nevertheless, larger spectral shifts were obtained for hydrogels, indicating that shifts of the chemical dissociation equilibrium was occurring in this last case. Slope changes of both intensity and wavelength maximum plots versus temperature occurred at the same temperature values, and we attributed the onset of the hydrogel thermal transition as the sol-gel transition occurring at T Х 370 K; at 320 K we observed the glass transition temperature of PVA plasticized by water molecules; at T Х 240 Ϯ 5 K we attributed the melting point of water molecules bonded to the PVA chains (freezable bond molecules); at T Х 270 Ϯ 5 K we observed the melting point of free water molecules (bulk water); and, at 135-145 K the water glass transition.

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“…Johari and co-workers studied the nanoconfined states of water and ice in the pores of poly(HEMA) hydrogels [6][7][8][9][10] by using calorimetry, dielectric spectroscopy, and diffraction measurements, and in the pores of silica [11][12][13][14] by calorimetry, and discussed the various interpretations of the state of nanoconfined water. In these matrices, the behavior is affected by the H 2 O's interactions with the hydroxyl groups in poly(HEMA) and the siloxane groups in silica pores.…”

Section: Introductionmentioning

confidence: 99%

Effect of pressure on thermal conductivity and pressure collapse of ice in a polymer-hydrogel and kinetic unfreezing at 1 GPa

Andersson

Johari

2011

The Journal of Chemical Physics

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We report a study of aqueous solutions of poly(vinylalcohol) and its hydrogel by thermal conductivity, κ, and specific heat measurements. In particular, we investigate (i) the changes in the solution and the hydrogel at 0.1 MPa observed in the 350-90 K range and of the frozen hydrogel at 130 K observed in the range from 0.1 MPa to 1.3 GPa, and (ii) the nature of the pressure collapse of ice in the frozen hydrogel and kinetic unfreezing on heating of its high density water at 1 GPa. The water component of the polymer solution on cooling either first phase separates and then freezes to hexagonal ice or freezes without phase separation and the dispersed polymer chains freeze-concentrate in nanoscopic and microscopic regions of the grain boundaries and grain junctions of the ice crystals in the frozen state of water in the hydrogel. The change in κ with temperature at 1 bar is reversible with some hysteresis, but not reversible with pressure after compression to 0.8 GPa at 130 K. At high pressures the crystallized state collapses showing features of κ and specific heat characteristic of formation of high density amorphous solid water. The pressure of structural collapse is 0.08 GPa higher than that of ice at 130 K. The slowly formed collapsed state shows kinetic unfreezing or glass-liquid transition temperature at 140 K for a time scale of 1 s. Comparison with the change in the properties observed for ice shows that κ decreases when the polymer is added.

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Glass-liquid transition of water and ethylene glycol solution in poly(2-hydroxyethyl methacrylate) hydrogel

Cited by 98 publications

References 0 publications

Prediction of entropy and dynamic properties of water below the homogeneous nucleation temperature

Prediction of entropy and dynamic properties of water below the homogeneous nucleation temperature

Thermal transitions of poly(vinyl alcohol) hydrogel sensed by a fluorescent probe

Effect of pressure on thermal conductivity and pressure collapse of ice in a polymer-hydrogel and kinetic unfreezing at 1 GPa

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