Structure and Properties of Fatigued Segmented Poly(urethaneurea)s III. Quantitative Analyses of Hydrogen Bond

Abstract

ABSTRACT:Hydrogen bonds in segmented poly(urethaneurea)s (SPUU) were studied with Fourier transform infrared spectroscopy (FTIR). Absorption curves due to the urethane and urea carbonyl groups were resolved into several peaks by a peak resolving method. Evaluation of individual peak intensity enabled one to estimate the amounts of hydrogen bonds formed with urea and urethane carbonyl groups, referred to as hydrogen bond indices, HvA and HvT• respectively. H vA and H VT were defined as the ratios of absorbances of hydrogen bonded carbonyl groups to free carbonyl groups, respectively for urea (UA) and urethane (UT) carbonyl groups. lt was found that the indices of hydrogen bonds of urethane and urea carbonyl groups were the parameters which represent phase mixing, i.e., dispersion of hard segments in the soft segment matrix, and the cohesive force in the hard segment domain. The variation of the indices of hydrogen bonds with increasing elongation and temperature indicated progress of tlie phase mixing and reduction of the cohesive force of the hard segment domain.KEY WORDS Segmented Poly(urethaneurea) / FTIR / Hydrogen Bond / Phase Mixing / Peak Resolving / Structure, morphology, mechanical and thermal properties, and antithrombogenicity of segmented poly(urethaneurea)s have been studied by many workers because not only for academic interest as multicomponent polymers but also for their industrial applications such as shock absorber, clothes, and medical materials. Most of the characteristic properties ofSPUUs, e.g., high elasticity, durability, antithrombogenicity are due to presence of the microphase separated structure and hydrogen bonds.points of structure and soft and hard segment orientations. The results showed that spherulites were selectively destroyed at the equatorial zone of the spherulite with respect to the stretching direction and then fragmented hard segments were dispersed in the soft segment matrix. Thus, phase mixing occurred. It was also shown that hydrogen bonds play an important role in the structural change in deformation.In previous papers in this series, 1 • 2 the deformation mechanism of segmented poly(urethaneurea)s (SPUUs) during uniaxial stretching and fatigue process were discussed based on deformations of spherulites from the view-* To whom correspondence should be addressed.In the case of SPUUs, the NH groups in the urea or urethane groups and the oxygen of the C = 0 groups in urea, urethane, polyether, or polyester behave as a proton donor and acceptor, respectively. Since hydrogen bonds af-· fect the physical properties, morphology and deformation mechanism of these materials, 895

Change in mechanical properties, composition, and structure of hydrated polyurethaneurea

“…7,12 As the temperature increases, the average strength of the hydrogen bonds decreases, indicating the progress of phase mixing and reduction in the cohesive force in the hard-segment domain. 1,11,27,36 Moreover, Sung et al, 1 Teo et al, 36 and Seymour and Cooper 37 further obtained the temperature for the dissociation of hydrogen bonding between hard-hard segments and between hard and soft segments by investigating the effect of temperature on the hydrogen bonding in PU and PUU.…”

Structure and properties of segmented poly(urethaneurea)s with relatively short hard-segment chains

“…Thus, C H is proportional to a ratio of the number of hydrogenbonded UA carbonyl groups to that of the MDI units; therefore, it can be approximately proportional to a fraction of the hydrogen bonds in UA carbonyl groups. The numerical peak decomposition was performed with peak-resolving software developed in our laboratory, 15 where the individual peak is assumed to be represented by a weighted sum of Gaussian and Lorentzian functions. Figure 1 shows the stress-strain curves for SPUUs at room temperature and plots of the tensile moduli versus x H , the average number of MDI units in the hard-segment chain (inset).…”

“…21 In the past, fundamental researches on structures in SPUs and SPUUs have been directed to reveal crystalline structures of hard segments and higher order structures of hard-segment domains, such as spherulites, as well as microdomain structures. [1][2][3][4][5][6][7][8][9][10][11][13][14][15][16][17][18][19][20] The hard segments of MDI-butanediol (BDO) were reported to give some diffraction arcs in a wide-angle X-ray diffraction pattern. 6,13,17 The arcs are broad and lack enough numbers so that identification of the space group for the crystalline structure is, in principle, impossible.…”

“…Moreover, the cohesive force in the hard-segment chains was quantitatively evaluated with Fourier transform infrared (FTIR) spectroscopy because the absorbance due to stretching vibrations of hydrogen-bonded UA carbonyl groups in the hard-segment chains could be separated out from the other absorption bands due to UT carbonyl groups. 5,12,15 …”

Caracterização térmica e dinâmico-mecânica de compósitos TPU/mica preparados em reômetro de torque

“…Os poliuretanos são materiais multicomponentes constituídos geralmente da reação de um diisocianato orgânico, um poliol e extensores de cadeia [1,2] . Em decorrência da grande quantidade de dióis e diisocianatos comercializados, surgem inúmeras possibilidades para a composição dos poliuretanos [3] .…”