Hydrogen-Bond Interactions between Urethane−Urethane and Urethane−Ester Linkages in a Liquid Crystalline Poly(ester−urethane)

Abstract

Five model compounds (Uu, Us, DPT, DMT, and MB) and two liquid crystalline poly(ester−urethane)s with inherent urethane and internal and external ester groups were prepared to monitor the hydrogen-bond (H-bond) interactions of urethane−urethane and urethane−ester (including internal and external esters). The model compounds were used to evaluate the extinction coefficient ratios between different free and bonded carbonyl absorption modes in the infrared spectra. The results show extinction coefficient ratios of εfree,u:εfree,ext:εbonded,ext:εbonded,u:εfree,int = 0.84:0.81:0.87:1.23:1.0. These ratios can then be used to approach mole fractions of different carbonyl groups in the oligomeric and polymeric poly(ester−urethane)s (as PEU-L and PEU-H, respectively) at different temperatures. For both PEU-L and PEU-H, their external ester carbonyl groups can compete efficiently with urethane carbonyl groups for H-bonds at elevated temperatures. Oligomeric PEU-L exhibited a major increase on the external ester carbonyl groups once heated to the mesomorphic state; in contrast, carbonyl variations on PEU-H proceeded in a continuous manner before the isotropization temperature. X-ray diffraction patterns suggest that PEUs form a smectic A layered structure. This result coupled with infrared study provided us the chain conformations of PEUs in their mesomorphic states.

Shape‐Memory Polymer in Response to Solution

“…The peak of bonded C=O that is relevant to this study has been marked out and identified according to some references. [16,17] The infrared band of free C=O stretching at 1724 cm -1 shifts to that of the bonded one at 1740 cm -1 . As such, the hydrogen bonding in the SMP is apparent.…”

Thermal properties and flame retardancy of an ether-type UV-cured polyurethane coating

“…But these bands are still detectable even above 325°C. Another peak that should be noticed is the absorbance at 1534 cm -1 , which is assigned to the C-N stretching and N-H deformation vibrations of the urethane group [8]. As can be seen at 150°C, this peak shifts to lower wave number at 1509 cm -1 , attributed to the N-H deformation of polyamine [5].…”

“…Radiation curing technology, mostly UV curing, offers many advantages during the curing process, in relation to the ecology or environment, energy conservation, economics and in the excellent performance of products [2][3][4]. The most commonly used UV-curable formulations involve unsaturated acrylic oligomers, including epoxy acrylates, polyester acrylates, polyether acrylates, urethane acrylates and silicone acrylates [5][6][7][8]. Among the oligomers used for UV-curable coatings, urethane acrylate oligomers offer a wide range of excellent application properties, such as high impact and tensile strength, abrasion resistance and toughness etc.…”

Preparation and Characterization of Nanocomposite Films from Chitin Whisker and Waterborne Poly(ester-urethane) With or Without Ultra-Sonification Treatment

“…Meanwhile, a shoulder peak centered around 3440 cm −1 for the films CW/WPU became obviously strong, implying that original inter-and intra-molecular hydrogen bonds in the WPU networks were destroyed resulting from the dispersion of chitin whisker within WPU matrix. Furthermore, the band at 2980-2850 cm −1 of films CW/WPU assigned to the stretching of methylene groups of the polyester soft segment became weaker than that of pure film WPU (28)(29)(30). The intensity of the peaks decreased with an increase of CW, and the extent of decrease is related to the blending ratio, also implying that abundant hydroxyl and acetamide groups in chitin whisker facilitate the formation of hydrogen bonding with NCO group in the hard segment of WPU.…”