Small-Angle Scattering Study of Mesoscopic Structures in Charged Gel and Their Evolution on Dehydration

Mesoscopic structures, with length scales ∼102 Å, were investigated by small-angle X-ray and neutron scattering (SAXS and SANS) in several N-isopropylacrylamide−sodium acrylate (NIPA−SA) copolymeric hydrogels with varying [NIPA]/[SA] ratios and water contents. The SAXS experiments reveal that, depen...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2003-07, Vol.107 (26), p.6300-6308
Main Authors: Sugiyama, Masaaki, Annaka, Masahiko, Hara, Kazuhiro, Vigild, Martin E, Wignall, George D
Format: Article
Language:English
Subjects:
ACRYLATES
DEHYDRATION
ELECTROSTATICS
HYDROGELS
NEUTRONS
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
POLYMERS
SCATTERING
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Summary:Mesoscopic structures, with length scales ∼102 Å, were investigated by small-angle X-ray and neutron scattering (SAXS and SANS) in several N-isopropylacrylamide−sodium acrylate (NIPA−SA) copolymeric hydrogels with varying [NIPA]/[SA] ratios and water contents. The SAXS experiments reveal that, depending upon the [NIPA]/[SA] ratio, the dehydrated NIPA−SA gel shows two mesoscopic structures:  one consists of randomly distributed SA-rich islands in NIPA matrix, while the other is a microphase-separated structure, composed of NIPA-rich and SA-rich domains. In addition, the SANS experiments reveal the mesoscopic structural features during the dehydration process. As the concentration of the network polymers increases, NIPA-rich and water-rich domains segregate in the gel. Then, an electrostatic interaction between the segregated domains induces a microphase-separated structure in the limit of the dehydrated NIPA−SA gel.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp0277816