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9 páginas, 16 figuras.The evolution of hydrogen bonding with temperature in three copoly(ether−urea)s with no phase separation has been studied by Fourier transform infrared spectroscopy (FT-IR) in the region of the carbonyl absorption of the urea groups. Assignment of the bands was made by supposing the existence of chains of urea groups linked by bifurcated hydrogen bonds. Quantum mechanical calculations of these chains fitted qualitatively with the experimental results. Dynamic mechanical and calorimetric experiments showed that the apparition of the band related to the “internal” urea groups of the chains produces a decrease in the glass transition of the polyether moiety of the copolymer and that prior to it a transition that we related to the glass transition of the bis(ureaphenyl)methane units takes place.We are indebted to the CICYT\ud(MAT 95-0099 and MAT 95-0020) and one of us (A.M.F.)\udthanks the UE (ERB4001GT921602) for the financial\udsupport.Peer reviewe

Hydrogen Bonding in Copoly(ether−urea)s and Its Relationship with the Physical Properties