SynopsisThe behavior of water contained in a hydrophilic hydrogel poly(hydroxyethy1 methacrylate) membrane and a hydrophobic hydrogel poly(methy1 methacrylate) membrane was studied by proton nuclear magnetic resonance (NMR) spectroscopy. Significant differences between the two hydrogels were observed in their relaxation times, the temperature dependence, and frequency dependence of these relaxation times, and changes of signal intensity of water protons on freezing and thawing. The water in these hydrogels was classified into three states: free, intermediate, and bound states. Poly(hydroxyethy1 methacrylate) contains relatively more water in bound and intermediate states than poly(methy1 methacrylate). The mobility of water decreases in the order, free water, intermediate water, bound water. The correlation times of the three states were roughly estimated to be lo-", s, respectively. The mobility of water in poly(methy1 methacrylate) is several orders of magnitude higher than that in poly(hydroxyethy1 methacrylate). In poly(hydroxyethy1 methacrylate), the exchange between intermediate and free water is slow in the NMR time scale: the apparent exchange rate and the activation energy were estimated to be 3.6 x lo2 s-' (28OC) and 2.0 kcal/mol, respectively. and

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SYNOPSISProperties of water in the wet membranes of a random copolymer of methyl methacrylate and methoxy poly (ethylene glycol) -monomethacrylate P ( MMA-co-Ml00G) and of a graft copolymer of vinyl chloride and methoxy poly (ethylene glycol) -monomethacrylate P (VCg-M100G) membranes were studied by proton NMR spectroscopy. Both polymers contain flexible polyoxyethylene side chains. Temperature and frequency dependences of relaxation times, changes of signal intensity of water protons on freezing and thawing, and saturation transfer were measured for both copolymers. These experimental results revealed that most of the bound water in these copolymers does not exist in a rigid state as suggested for the other hydrogels. The introduction of flexible hydrophilic side chains resulted in high mobility of the water molecules bound to the side chains (the apparent correlation time 7, -lo-'' s ) . For the graft copolymer P ( VC-g-M100G) , hydrophilic polyoxyethylene side chains are contiguous to each other. Because of the interaction between the side chains, the mobility became more complex than that for the random copolymer P ( MMA-co-M100G) . The difference in the mode of mobility of water on the membrane surface may be related to the difference of the membrane characteristics of these copolymers.

Temperature dependent conformations and molecular motions of pyrimidine polyribonucleotides, poly(C) and poly(U), have been studied in 2H2O solutions (pH 5.8±0.3, 5–72 °C by measuring 1H NMR intensities, chemical shifts, coupling constants, and spin-lattice relaxation times. Below 50 °C, poly(C) exists as a slowly exchanging mixture of double-stranded and single-stranded forms of which only the single-stranded form is observable by 1H NMR. In this temperature range, the single-stranded poly(C) shows a strong base-stacking with dominated C3′-endo anti conformation, whereas above 50 °C it takes partly C2′-endo conformation with destabilization of the helical structure. Poly(U) exists as single strand within the whole temperature range studied, and the bases are nearly unstacked with 58% of C2′-endo conformer. Poly(U) is more flexible than poly(C), which was characterized with rotational correlation times in the order of 10−9–10−10 s.