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Journal Articles

Neutron diffraction of ice and water in hydrogels

Sekine, Yurina; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Suzuya, Kentaro; Fujisaki, Fumika*; Ikeda, Kazutaka*; Otomo, Toshiya*; Fukazawa, Tomoko*; Yamauchi, Hiroki; et al.

JPS Conference Proceedings (Internet), 8, p.033009_1 - 033009_6, 2015/09

Neutron diffraction profiles of low-D$$_{2}$$O-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured from 100 to 300 K to investigate the structure and properties of water in hydrogels. A broad diffraction observed at temperatures lower than 220 K indicates the existence of amorphous ice in the hydrogels at low temperatures. During the heating process, diffraction peaks from ice crystals appear in the profiles. These peaks indicate that cubic ice and hexagonal ice exist at T $$geq$$ 220 K. We refined the structure parameters of these ices in the hydrogel, which indicate the existence of low-density ice in the hydrogel.

Journal Articles

Dependence of structure of polymer side chain on water structure in hydrogels

Sekine, Yurina; Takagi, Hajime*; Sudo, Sayoko*; Kajiwara, Yutaro*; Fukazawa, Hiroshi; Fukazawa, Tomoko*

Polymer, 55(24), p.6320 - 6324, 2014/11

 Times Cited Count:14 Percentile:53.72(Polymer Science)

To investigate the effects of structure of polymer side chains on structure of water in hydrogels, Raman spectra of polyacrylamide (PAA) and poly-$$N$$,$$N$$-dimethylacrylamide (PDMAA) hydrogels were measured. PAA and PDMAA have similar chemical structures, except for the side chain structure. The result shows that the frequency of the OH stretching mode for the PAA hydrogel decreases as the water content decreases, while that for the PDMAA hydrogel increases. We conclude that most of the bound water molecules in the PAA hydrogel form four strong hydrogen bonds with the hydrophilic groups in the side chain of PAA, whereas those in the PDMAA hydrogel form weak hydrogen bonds with surrounding water molecules. The water structure is an important factor governing the physical and chemical properties of gel materials.

Journal Articles

Neutron diffraction of ice in hydrogels

Sekine, Yurina; Fukazawa, Tomoko*; Aizawa, Mamoru*; Kobayashi, Riki*; Chi, S.*; Fernandez-Baca, J. A.*; Yamauchi, Hiroki; Fukazawa, Hiroshi

Journal of Physical Chemistry B, 118(47), p.13453 - 13457, 2014/08

 Times Cited Count:1 Percentile:2.1(Chemistry, Physical)

Neutron diffraction patterns for deuterated poly-$$N$$,$$N$$,-dimethylacrylamide (PDMAA) hydrogels were measured from 10 to 300 K to investigate the structure and properties of water in the gels. Diffraction peaks observed below 250 K indicate the existence of ice in the hydrogels. Some diffraction peaks from the ice are at lower diffraction angles than those in ordinary hexagonal ice (Ih). These shifts in peaks indicate that the lattice constants of the $$a$$ and $$c$$ axes in the ice are about 0.29% and 0.3% higher than those in ice Ih, respectively. The results show that bulk low-density ice can exist in PDMAA hydrogels. The distortions in the lattice structure of ice imply significant interactions between water molecules and the surrounding polymer chains, which play an important role in the chemical and mechanical properties of the hydrogel.

Journal Articles

Structural changes of water in poly(vinyl alcohol) hydrogel during dehydration

Kudo, Kushi*; Ishida, Junichi*; Syuu, G.*; Sekine, Yurina; Fukazawa, Tomoko*

Journal of Chemical Physics, 140(4), p.044909_1 - 044909_8, 2014/01

 Times Cited Count:41 Percentile:89(Chemistry, Physical)

To investigate the mechanism of structural changes of water and polymer networks with drying and swelling, we measured the Raman spectra of a physically cross-linked poly(vinyl alcohol) (PVA) hydrogel synthesized using the freezing thawing method. On the basis of the dependence of the frequency shifts on the PVA concentration of the original solution, it was found that the structure of the polymer network in the reswollen hydrogel becomes inhomogeneous due to shrinkage of the polymer network with drying. Furthermore, to investigate the effects of the cross-linking structure on the drying process, these results were compared with those of a chemically cross-linked PVA hydrogel synthesized using glutaraldehyde as a cross-linker. The results show that the structures of the polymer network and water change with the gel preparation process, cross-linking method, and drying and reswelling processes.

Journal Articles

Effects of crosslinker density on the polymer network structure in poly-$$N$$,$$N$$-dimethylacrylamide hydrogels

Fukazawa, Tomoko*; Ikeda, Naohiro*; Tabata, Mayu*; Hattori, Masataka*; Aizawa, Mamoru*; Yunoki, Shunji*; Sekine, Yurina

Journal of Polymer Science, Part B; Polymer Physics, 51(13), p.1017 - 1027, 2013/07

 Times Cited Count:23 Percentile:67.39(Polymer Science)

Oral presentation

Ice structure formed in saccharide solution

Sekine, Yurina; Fukazawa, Tomoko*; Kajiwara, Yutaro*; Ito, Yu*; Fukazawa, Hiroshi

no journal, , 

no abstracts in English

Oral presentation

Structure of water and ice in poly-N,N,-dimethylacrylamide hydrogel

Sekine, Yurina; Fukazawa, Tomoko*; Yamauchi, Hiroki; Songxue, C.*; Chakoumakos, B.*; Fernandez-Baca, J. A.*; Fukazawa, Hiroshi

no journal, , 

Neutron diffraction data of deuterated poly-N,N,-dimethylacrylamide (PDMAA) hydrogel were measured at temperatures of 10 - 290 K in order to investigate the structure and properties of water in the hydrogel. Diffraction peaks observed below 270 K indicate the existence of a solid ice in the hydrogel. The positions of some peaks from the ice are lower than those in ordinary hexagonal ice (Ih). The lower shifts of the peaks indicates that the lattice constants of the c-axis in the ice are about 0.3% higher than those in ice Ih, whereas those of the a-axis are almost consist. The results show that bulk of a low-density ice crystal exists in the PDMAA hydrogel. The water molecules, which have a significant interaction with the polymer chains, play an important role in the chemical and mechanical properties of the hydrogel.

Oral presentation

Neutron diffraction study of hydrogels

Sekine, Yurina; Fukazawa, Tomoko*; Kobayashi, Riki*; Chi, S.*; Fernandez, J.*; Fukazawa, Hiroshi

no journal, , 

Hydrogels are unique materials that can contain a large amount of water in their three-dimensional polymer chain networks. We used neutron diffraction to probe the structure of D$$_{2}$$O in poly-$$N$$,$$N$$,-dimethylacrylamide (PDMAA) hydrogel. Two PDMAA hydrogels with high and low D$$_{2}$$O-content W (W = 0.9 and 0.5) were prepared. The neutron diffraction measurements were performed using the Wide Angle Neutron Diffractometer (WAND) at the High Flux Isotope Reactor in Oak Ridge, U.S.A. The samples were rapidly cooled using liquid nitrogen, and then heated from 10 to 300 K. The neutron diffraction profiles of the high D$$_{2}$$O-content PDMAA gel (W = 0.9) have strong sharp peaks below 270 K that are similar to diffraction patterns of hexagonal ice Ih. At 300 K, the profile has a broad liquid-like diffraction feature. The profile of the gel at W = 0.5 has a broad band in the 2$$theta$$ range from 20$$^{circ}$$ - 28$$^{circ}$$ below 230 K that are similar to diffraction pattern of glassy water. Sharp peaks are observed in the profile at 230 K. The feature of the profile is similar to that of cubic ice. The profile at 260 K has ice Ih-like strong peaks. Our neutron diffraction results show the existence of ice in hydrogels and that the structure of ice depends on the water content of the hydrogel. The structural changes of ice in hydrogels might have important implications in the interpretation of hydrogel properties, for both biological tissues and synthetic gel materials.

Oral presentation

Structural changes of water in polyacrylamide hydrogels

Sekine, Yurina; Tojima, Yu*; Fukazawa, Tomoko*; Fukazawa, Hiroshi

no journal, , 

Hydrogels are unique materials that can contain a large amount of water in their three-dimensional polymer chain networks. Because of characteristic properties of water, hydrogels are widely used as biomedical materials. The structure of water is thus an important factor governing the chemical and physical properties of hydrogel materials. In order to investigate the effects of the side groups of polymer on the water structure, we measured the Raman spectra of polyacrylamide and poly-N,N-dimethylacrylamide hydrogels with various water contents. The results indicate that the water structure in the hydrogels depends on the structure of the side groups in the polymer chains.

Oral presentation

Neutron diffraction study of chemically cross-linked hydrogels

Sekine, Yurina; Chi, S.*; Fernandez Baca, J.*; Fukazawa, Tomoko*; Fukazawa, Hiroshi

no journal, , 

Neutron diffraction profiles of high and low- D$$_{2}$$O-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured from 100 to 300 K to investigate the structure and properties of water in hydrogels. For high D$$_{2}$$O content hydrogel, strong sharp peaks are observed in 100 to 250 K. The feature of the peaks is similar to that of hexagonal ice (ice Ih). For low D$$_{2}$$O-content hydrogel, a broad band is observed at temperatures less than 220 K. The result indicates the existence of amorphous ice in the hydrogel. During the heating process, diffraction peaks from ice crystals appear in the profiles. The peaks indicate that cubic ice and hexagonal ice exist at temperatures above 220 K. We first obtained structure parameters of these ices in the hydrogel, which indicate the existence of low-density ice in the hydrogel.

Oral presentation

Structure of water and ice in poly-N,N,-dimethylacrylamide hydrogels investigated by neutron diffraction

Sekine, Yurina; Tojima, Yu*; Fukazawa, Tomoko*; Fukazawa, Hiroshi

no journal, , 

Neutron diffraction patterns of high and low D2O-content poly-N,N,-dimethylacrylamide (PDMAA) hydrogels were measured in temperature range from 10 to 300 K to investigate structure of water in hydrogels. The results show that amorphous, cubic, and hexagonal ices exist in the low D2O-content PDMAA hydrogel at low temperature, whereas only hexagonal ice exists in the high D2O content PDMAA hydrogel.

Oral presentation

Structure of water in hydrogels investigated by neutron diffraction

Sekine, Yurina; Chi, S.*; Fernandez Baca, J.*; Fukazawa, Tomoko*; Fukazawa, Hiroshi

no journal, , 

Hydrogels are unique polymer materials consisting of large amount of water in their three-dimensional networks. The structure of water is an important factor governing the chemical and physical properties of gel materials. To investigate structure and properties of water in poly-N,N,-dimethylacrylamide (PDMAA) gel, neutron diffraction and differential scanning calorimetry (DSC) curve of the high (90wt%) and low (55wt%) D$$_{2}$$O content gels were measured. The neutron diffraction patterns show that amorphous, cubic, and hexagonal ices exist in the low D$$_{2}$$O content gel at low temperature, whereas only hexagonal ice exists in the high D$$_{2}$$O content gel. The DSC result shows that the low D$$_{2}$$O content gel contains only intermediate and bound water. In contrast, high D$$_{2}$$O content gel contains free, intermediate, and bound water. Therefore the results indicate that amorphous and cubic ices are only formed when the hydrogels do not have the free water.

Oral presentation

Structure of water and polymer network in poly(vinyl alcohol) hydrogels with repeated freezing-thawing cycles

Sekine, Yurina; Ishikawa, Nozomi*; Fukazawa, Tomoko*

no journal, , 

no abstracts in English

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