In the present work, the effect of heteroatomic hydrogen bonding on the properties of −OH/–NH-terminated soft-segment-free polymers, viz, polyurethane (P-UT), polyurea (P-UR), and their hybrid (P-UT–UR), is explored. P-UT was synthesized from phloroglucinol and P-UR was synthesized from 1,3,5-triazine-2,4,6-triamine by employing hexamethylene diisocyanate as a counterpart. P-UT exhibited a spherulitic structure with varying sizes, whereas P-UR displayed a fibrillar structure characteristic as that of crystalline hard segments. The P-UT–UR hybrid exhibited a fine nanospherulitic structure with a high order of interconnectivity. Negative surface skewness values of −0.47 and −0.18 were measured (by AFM) for P-UT and P-UT–UR, respectively, which revealed that the surface is not smooth and is covered with features. Due to the increased H-bonding (−N–H···O–H) in P-UT–UR, its transparency decreased. A block copolymer hybrid of urethane–urea was synthesized, which preferred homoatomic H-bonding, whereas random urethane/urea bridges favored hetreoheteroatom H-bonding. A pentafluorophenyl end-functional hybrid (PFI–P-UT–UR) was synthesized, which displayed filaments of ∼2–3 μm length in contrast to the interconnected nanospherulitic structure observed for P-UT–UR. The self-aggregation and end folding led to the formation of a filament structure. By altering the chemical structure slightly, nano-ordered polyurethanes or their hybrids can be achieved.
Functional and re‐processable polyurethane (soft‐segment free, FPU) is synthesized and later it is converted into substituted PUs by reaction with suitable molecules to enrich/block H‐bonding features inherent with FPU. By these substitutions, H‐bonding is easily altered as observed in FTIR investigations. Spherical morphology of FPU turned into elongated/twisted one due to the separation of polymer chains by these molecules (bulky or long chain groups). Owing to the presence of hydroxyl groups, the dissociation of FPU on re‐processing at 150°C was dodged and achieved heat‐healable PUs. Interestingly, a trivial quantity (2.5 wt%) of FPU in an epoxy‐amine cross‐linked structure increased the elongation to nearly fourfold (5%‐21%). The soft‐segment free nature of PU and its functional groups have key role in facilitating easy incorporation of PU into epoxy matrices to provide exotic properties.
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