Hydrogen-Bond Interactions between Ester and Urethane Linkages in Small Model Compounds and Polyurethanes

Abstract

Four model compounds (Us, Uu, UEex, and UEin) and two polyurethanes (PU1 and PU2) were prepared to monitor the hydrogen-bond (H-bond) interactions of urethane−urethane and urethane−ester (including external and internal esters). The results from differential scanning calorimetry (DSC) and X-ray diffraction suggested that the infrared absorption patterns in the −NH and −CO regions are closely related to the thermal history of the test specimen. Except for the incapability of the internal ester −CO to form an H-bond with urethane −NH, five −CO absorption bands can be assigned and attributed to free internal ester, free urethane, free external ester, bonded external ester, and disordered and ordered bonded urethane absorptions. The frequencies of the respective −CO band maxima obtained from the model compounds were given. In cases of polyurethanes, the −CO absorption of the amorphous PU1 was assigned on the basis of the deconvoluted result of a heat-treated UEex, while the liquid crystalline PU2 has its −CO absorptions assigned on the basis of the physical states of the test specimen. The as-reacted PU2 has its −CO absorptions closely related to the heat-treated UEin; however, as PU2 was heated into the mesophase, the orientation order caused the corresponding −CO absorptions similar to those for the as-reacted UEin.

Preparation and properties of water‐borne polyurethane with branched straight aliphatic chains

“…The stretching vibration peaks of NAH bond and C¼ ¼O bond are strongly dependent on the strength and kinds of hydrogen bond in polyurethane. 16,17 The hydrogen bond is formed only between NAH and C¼ ¼O of urethane group on the surface of CWPU film, which results in the lower band of C¼ ¼O stretching vibration. In the bulk of CWPU film, NAH can form hydrogen bond with both C¼ ¼O of urethane group and AOA linkage in structure of polyols, which reduces the strength of hydrogen bond derived from C¼ ¼O of urethane group, therefore, the stretching vibration of C¼ ¼O of urethane group in bulk CWPU film shift to higher band 1715 cm À1 .…”

On The Micro‐Phase Separation in Waterborne Polyurethanes

“…The presence of hydrogen bonds in PUs can be highlighted by FTIR spectroscopy, [25][26][27][28][29][30][31] that also allows the identification of the main functional groups present in their molecular structure. In Figure 7 and 8 the FT IR spectra of the original polycarbonate and polyester based PUs are shown; in Table 4 the main peaks assignments related to the principal bands are summarised.…”

Calix[4]arenes Used as a New Type of Chain Extender in the Preparation of Polyurethanes

“…The urethane linkages in PUs can serve as a hydrogen-bond acceptor and donor. [20] Five bands were observed in the -C=O stretching region. The bands at 1743 and 1728 cm −1 are attributed to free ester (CO f ,e ) and free urethane (CO f ,u ), respectively, while the bands at 1714 and 1695 cm −1 are associated with short-range (CO b,u ) and long-range (CO b,u ) hydrogen-bonded urethane, respectively.…”