Properties of Water-Absorbed Polyurethane Ionenes

Abstract

Crosslinked polyurethane (PU) ionenes were prepared. NCO-terminated prepoly mer obtained from polyol blends of poly(oxytetramethylene)glycol (PTMG) and poly(oxyeth ylene)glycol (PEG) and 4,4'-methylenebis(phenylisocyanate) were made to react with 2- dimethylaminoethanol, resulting in amine-terminated (AT) prepolymer having isocyanurate ring in structure. By the reaction of AT-prepolymer with N,N,N' ,N'-tetramethyl-1,6-diaminohexane and 1,6-dibromohexane, crosslinked PU ionenes were obtained. Bound water existing in the hydrogel of crosslinked PU ionenes was determined by two methods. The amount of nonfreezing (bound) water determined by DSC was constant, ca. 9 water mol/[N+] mol, and not dependent upon the composition of PU ionenes. This type of water is considered to be the water strongly bound to [N+] ion site. On the other hand, the amount of bound water determined by drying measurement was greater than that determined by DSC measurement. In the drying mea surement, PU ionene containing larger amounts of PEG had larger amounts of bound water. The bound water determined by drying is considered to include water hydrated to polar ether [O] group in addition to nonfreezing water. 95 % of water existing in swollen hydrogel was free water, as in highly water-absorbing resin. Tensile properties of swollen gels were examined. It was suggested that the ionic aggregation that existed in dry state was destroyed in swollen state.