INVESTIGATION OF INTERACTIONS IN POLYETHER-POLYURETHANES AND THEIR MIXTURES WITH OTHER POLYURETHANES BY HIGH-RESOLUTION NMR

The hydrogen bonds in polyether-polyurethanes based on 4,4'-diphenylme thane diisocyanate, N-methyl-diethanolamine (MDEA) and poly(tetramethy lene oxide) glycol (PTMG) and their zwitterionomers were investigated by high resolution H-1 n.m.r. in deuterated dimethyl formamide. There are four NH peaks in each of the H-1 n.m.r. spectra resulting from fou r kinds of hydrogen bonds. The NH groups in the hard segments may form hydrogen bonds with the C=O groups of the hard segments, the N atoms of the MDEA portions, the S=O groups of gamma-propanesulfonates and th e O atoms of PTMG. The relative amounts and chemical shifts of the NH peaks do not change with polyurethane concentration. Mixtures of polye ther-polyurethanes with a polysiloxane-polyurea and a polyester-polyur ethane were also studied by H-1 n.m.r. There are no hydrogen-bonding i nteractions between the hard segments of the two different polyurethan es in these mixtures. The hard segments of the two different polyureth anes cannot be mixed at the molecular level. This is proven by nuclear Overhauser effect spectroscopy (NOESY) for a mixture of a polyether-p olyurethane with a polysiloxane-polyurea. The NOESY spectrum indicates that the soft segments of the two different polyurethanes can be mixe d at the molecular level. Most of the hard segments form microdomains in concentrated solution. Neither the solvent nor water can invade the microdomains rich in hard segments. Thus we can study hydrogen-bondin g interactions in concentrated solution and deduce those interactions in the solid state.