¹H‐NMR studies on water in methacrylate hydrogels. I

Abstract

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

Hydration of Hydroxypropylmethyl Cellulose: Effects of pH and Molecular Mass

“…Therefore, the T 2 measurements of acidic solvent protons presented in Fig. 3 have been interpreted, like in other polysaccharides gels [21][22][23][24][25], in terms of a fast exchange which takes place between the free and bound state of water. However, in order to explain the reduction in the relaxation time observed for neutral and especially for acidic solvents, we have to assume that in addition to the fast exchange of water molecules, other mechanisms of the relaxation take place.…”

The Relationship Between Water Structure and Blood Compatibility in Poly(2-methoxyethyl Acrylate) (PMEA) Analogues

“…[13] Tightly bound (non-freezing) water has a NMR correlation time (t c ) value of 10 À8 -10 À6 s and does not crystallize even at À100 8C. [12,13] Loosely bound (intermediate) water has a t c value of 10 À10 -10 À9 s and exhibits melting/crystallization at temperatures below 0 8C. [12,13] Free water has t c value of 10 À12 -10 À11 s and crystallizes at 0 8C.…”

“…[12,13] Loosely bound (intermediate) water has a t c value of 10 À10 -10 À9 s and exhibits melting/crystallization at temperatures below 0 8C. [12,13] Free water has t c value of 10 À12 -10 À11 s and crystallizes at 0 8C. [12,13] In addition, we have reported that the intermediate water is formed in a wide variety of biopolymers including proteins (albumin and gelatin), [14,15] polysaccharides (hyaluronan and chondroitin sulfate) and nucleic acids (DNA and RNA).…”

Study on physicochemical properties of thermosensitive hydrogels constructed using graft‐copolymers of poly(N‐isopropylacrylamide) and Guar gum

“…9 The water in hydrogels can be generally classified into three species: free water, freezing bound water, and nonfreezing bound water. Nonfreezing bound water, linking with hydrophilic group of the polymer network by hydrogen bond, does not freeze even at extra low temperature.…”

“…It is difficult to distinguish the melting peaks of freezing bound water and free water, so they are calculated together. 9 The water states in GPNA hydrogels were studied by DSC.…”