Morphology and chain dynamics during collapse transition of PNIPAM gels studied by combined imaging, relaxometry and Xe-129 spectroscopy techniques

TitleMorphology and chain dynamics during collapse transition of PNIPAM gels studied by combined imaging, relaxometry and Xe-129 spectroscopy techniques
Publication TypeJournal Article
Year of Publication2005
AuthorsKariyo, S, Kuppers, M, Badiger, MV, Prabhakar, A, Jagadeesh, B, Stapf, S, Blumich, B
JournalMagnetic Resonance Imaging
Volume23
Issue2
Pagination249-253
Date PublishedFEB
ISSN0730-725X
Keywordsgel, networks, phase transition, relaxometry, Xe-129 spectroscopy
Abstract

The temperature-induced shape transition of poly(N-isopropylacrylamide) gels of different cross-link densities was investigated by a combination of NMR techniques allowing the characterization of both the macroscopic collapse as well as the changes on a molecular scale related to the expulsion of water from the gel network. The proton-containing gel phase was visualized by swelling in heavy water, and the volume change was monitored by proton imaging for cross-link densities between 0.5 % and 2.5 %. Above the transition temperature of 35 degrees C, gel collapse led to a volume change of up to a factor of 17 for the gel of smallest cross-link density. Two spectral lines of Xe-129 are found in the gel state and are assigned to the hydrophobic and hydrophilic parts of the network. In the collapsed state, the hydrophobic peak shows a strong shift while the hydrophilic peak disappears. A considerable shortening of both T-1 and T-2 of the gel protons upon collapse was found at a field of 4.7 T. At lower fields, the effect becomes more pronounced and qualitatively different dispersion behaviors between the swollen and the collapsed states are observed. (c) 2005 Elsevier Inc. All rights reserved.

DOI10.1016/j.mri.2004.11.019
Type of Journal (Indian or Foreign)

Foreign

Impact Factor (IF)1.980
Divison category: 
Chemical Engineering & Process Development
Polymer Science & Engineering