The Effect of Synthetic Conditions on the Free Volume of Poly(2-hydroxyethyl methacrylate) as Studied by ~1H NMR, ~(129)Xe NMR, and Position Annihilation Spectroscopy

摘要

The porous structure of PHEMA hydrogels prepared under a range of conditions has been examined using three distinct probes. Positron annihilation lifetime spectroscopy and ~(129)Xe NMR are sensitive to pores in the range 0.1-10 nm, while ~1H NMR of water within the hydrogel provides information on a range of sizes up to several microns. PHEMA samples were prepared in solution with from 5-30 wt. % of water in the polymerization mixture. Below 30 wt. % the water exists in nanometer-sized pores, and above this a substantial proportion reside in micron sized pores. The PALS and ~(129)Xe NMR results support the existence of relatively hydrophobic domains of sub-nanometer size.