Water structure of poly(2-methoxyethyl acrylate) observed by nuclear magnetic resonance spectroscopy.

Poly(2-methoxyethyl acrylate) (PMEA) is well known to show excellent blood compatibility. The reason for its performance has been attributed to the existence of cold crystallizable water in PMEA observed using differential scanning calorimetry (DSC). However, there is little known about the property of water in PMEA over 0 °C, especially at ambient temperature including body temperature, because blood compatibility is observed at 37 °C. The present study was performed to clarify the state of water at the temperature ranging from 15 to 45 °C using a solution nuclear magnetic resonance spectroscopy (NMR). In addition, water in poly(butyl acrylate) (PBA) was used as a control, which exhibited poor blood compatibility. In the NMR spectra of water in PMEA, two peaks appeared at 4.87 and 3.71 ppm at 30 °C, showing the existence of two types of water structure. The peak intensity of the upfield water is considerably higher than that of the downfield water. On the other hand, the hydrated PBA showed only one peak at 4.98 ppm at 30 °C. The dynamic property of water in these polymers was estimated from the deuterium solution NMR spin-lattice relaxation time, T1 2H . The T1 2H values of peaks observed at 4-5 ppm were relatively large, denoting rapid motion, while the values of water at 3.7 ppm in PMEA were small, denoting slow mobility. Thus, the state of water molecules in PMEA were different from those in PBA at ambient temperature in terms of chemical shift and mobility.