Crystallinity and hydrogen bonding of hard segments in segmented poly(urethane urea) copolymers

Studies on the effect of virtual crosslinking on the hydrolytic stability of novel aliphatic polyurethane ureas for blood contact applications

“…Moreover, the absence of the peak at 1666 cm −1 for C=O stretching of urea carbonyl bonded (disordered) in the polymers HFL9-PU1 and HFL13-PU2 clearly indicated the formation of short-and longrange ordering of urea hydrogen bonding, which indicated crystallites in hard domains as reported elsewhere. 31,32 The disordered urea hydrogen bonding (1666 cm −1 ) could be observed in the IR spectrum of solid segmented polyurethane urea samples. 31 This study revealed the presence of micro-crystallite formation in hard segments despite the isomeric forms of the H 12 MDI attributed to extensive hydrogen bonding interactions, which were hitherto observed only in aromatic polyurethane ureas.…”

“…31,32 The disordered urea hydrogen bonding (1666 cm −1 ) could be observed in the IR spectrum of solid segmented polyurethane urea samples. 31 This study revealed the presence of micro-crystallite formation in hard segments despite the isomeric forms of the H 12 MDI attributed to extensive hydrogen bonding interactions, which were hitherto observed only in aromatic polyurethane ureas. The extensive hydrogen bonding between urea-urea groups in these polyurethane ureas imparted physical crosslinking (virtual crosslinking) leading to three-dimensional crosslink- ing in hard domains.…”

Synthesis and Characterization of New Polyurea Elastomers by Sol/Gel Chemistry

“…[13,14] Generally, the reaction for obtaining linear polymers (thermoplastic block copolymers) takes place between a diisocyanate (aromatic or aliphatic) with an aminoterminated prepolymer or resin (generally aliphatic). [8,10,[14][15][16][17][18][19][20][21][22][23] The prepolymer or resins contains both soft segments with low glass transition temperatures and amorphous melts, and hard domains with high glass transition and high melting temperatures due to hydrogen bonding [24,25] as physical crosslinks. Little work has been done for the synthesis and study of polymer networks because of the fast reactivity during chemical crosslinking, except by using spray or reaction injection molding.…”

High‐Throughput Screening of Mechanical Properties on Temperature‐Gradient Polyurethaneurea Libraries

“…These peaks are identified as: (i) free urea carbonyl, n ¼ 1690-1695 cm À1 , (ii) disordered H-bonded urea carbonyl, n ¼ 1650-1655, and (iii) ordered (i.e., within hard domains) H-bonded urea carbonyl, n ¼ 1640-1645. [3][4][5] We note that analysis of the NCO peak at 2260 cm À1 showed that conversion was complete at all T values explored. The total mole fraction of H-bonded urea (X T,UA ) and the fraction of ordered H-bonded urea (X O,UA ) was calculated using the approach of Ning et al [3] Since thermal energy favors H-bond dissociation, X T,UA decreases continuously with an increase in cure T, as shown in Figure 1.…”

“…For example, the morphology and extent of H-bonding depends on cure temperature (T) and time, as characterized using FT-IR spectroscopy, differential scanning calorimetry (DSC), atomic force microscopy (AFM), and X-ray diffraction. [1][2][3][4][5] However, efficient exploration of these effects is an expensive, time-consuming task using conventional 1-sample-for-1-measurement techniques. We recently reported a T-gradient combinatorial library approach to characterizing the effects of processing on polymers, used to investigate phase separation and wetting phenomena.…”