Hybrid poly(hydroxy urethane)s
(PHUs) are synthesized by copolymerizing aromatic/alicyclic cyclic
carbonates with a polyether amine via addition polymerization. They
result into polymers with an average molecular weight of 10 kDa and
exhibit solubility in common organic solvents. The hybrid PHUs display
T
g
up to 18 °C. PHUs are enriched with multiple
H-bonded interactions and they are assessed using temperature-dependent
1
H NMR and Fourier-transform infrared studies. PHUs possess
folded-sheet morphology with nanogap between folds and nanowidth between
chains. The secondary interactions bestow thermoreversible property
to PHUs, and they display good adhesion to both polar (Al–Al)
and nonpolar (HDPE–HDPE) substrates. Hybrid PHUs show improved
optical transparency compared to homo PHUs. The PHUs are thermally
stable up to 250 °C.
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.
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