Hydrogen bonding properties of ether-based urethane prepolymers and polyurethane elastomers

Isocyanate-terminated urethane prepolymers (ITUP) and polyurethane elastome rs (PUE) have been prepared by the reaction of 4,4 ' -methylenebis(phenyl) diisocyanate with polyether diols such as or hydro-omega -hydroxypoly (oxyp ropylene) (PPG) or alpha -hydro-omega -hpdroxypoly (oxytetramethylene) (PTM G) of various molecular weights. Characterization of the ITUP and the PUE h as been carried out by means of differential scanning calorimetry and FTIR spectroscopy. In this article, discussion is made with the interaction deve lopment between soft and hard segments on the basis of the evaluated glass- transition temperatures (T-g) and the hydrogen bond interaction among the u rethane- and the ether-linkages in molecular chain. The T-g values of ITUP and PUE are considerably high in comparison with those of only the PPG and the PTMG. This implies that the micro-Brownian motion of the oxypropylene a nd the oxytetramethylene moiety is restricted by the hard segment which con tains the urethane linkages having a high activity of the hydrogen bond int eraction. Physical crosslinks by the hydrogen bond in the ITUP and PUE are formed between the soft segment and the hard segment and between the hard s egment and the hard segment, and the degree of crosslinking is higher with the latter. The PPG-based NHC-O-C(%) is higher than the PTMG-based one, whe reas the PPG-based NHC=O(%) is lower than the PTMG-based one. Thus rigid ha rd domain is formed rather with the PTMG-based one.