Water properties in the super-salt-resistive gel probed by NMR and DSC.
The so-called "super-salt-resistive gel", or poly(4-vinylphenol) (P4VPh) hydrogel, of different water contents ( H = 97-51%) was prepared by cross-linking with different amounts of ethylene glycol diglycidyl ether. 1H NMR spectroscopy was used to investigate the dynamic properties of water in the gel samples in terms of the spin-spin relaxation. The T2 values in those hydrogels were analyzed by assuming a two-component system, namely, T 2(long) and T2(short), and their fractions were obtained. In the higher water content region (75% < or = H < or = 97%), T2(long) for P4VPh gel was almost constant or even slightly increased with decreasing temperature. On the other hand, T2(long) for poly(vinyl alcohol) (PVA) gel (80% < or = H < or = 96%) significantly decreased with decreasing temperature, showing a natural behavior for water mobility in common hydrogels. Water in P4VPh gels of lower water contents ( H = 70% and 51%) also showed intriguing behaviors: the T2 values are much larger than those of gels with higher water contents and decreased with decreasing temperature only in the lower temperature range (<10 degrees C). The fraction of T2(long) values of P4VPh gel showed another contrast to those of PVA gel; the latter decreased with decreasing water content (normal behavior), while in the former gel the highest fraction (ca. 60% at 20 degrees C) was observed for a sample with the lowest water content ( H = 51%). On the other hand, the results of DSC measurements for P4VPh gel were less specific than those of T2 and comparable to those of common hydrogels such as PVA; with decreasing water content, the total amounts of free water and freezable bound water per polymer mass (g/g) decreased, while the amount of nonfreezing water per polymer also decreased.
Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
Yuko
Y
Sakai
Shigeki
S
Kuroki
Mitsuru
M
Satoh
D002152:Calorimetry, Differential Scanning; D003432:Cross-Linking Reagents / Q000737:chemistry; D005782:Gels / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D011142:Polyvinyl Alcohol / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D012492:Salts / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
D003432:Cross-Linking Reagents; D005782:Gels; D011145:Polyvinyls; D012492:Salts; C509677:poly(4-vinylphenol); D014867:Water; D011142:Polyvinyl Alcohol