Polyurethane elastomers
(PUEs) containing trans-1,4-bis(isocyanatomethyl)cyclohexane
(1,4-H6XDI) have been synthesized by polymerizing 1,4-H6XDI with
poly(oxytetramethylene) glycol and 1,4-butanediol. The molecular
aggregation state and mechanical properties of these PUEs have been
compared with those exhibited by PUE analogues made of MDI and diols.
The hard segment chains in the 1,4-H6XDI-based PUEs are
found to readily crystallize and form strong hydrogen bonds due to
a high symmetry of 1,4-H6XDI molecule. Consequently, the
1,4-H6XDI-based PUEs exhibit well-organized hard segment
domains. This leads to their generally superior mechanical properties
as compared to those of the well-known MDI-based PUEs. 1,4-H6XDI’s lack of aromatic moieties is expected to greatly enhance
color stability of resulting PUEs. All the above features suggest
1,4-H6XDI could replace MDI in a range of applications.
Changes
in the microphase-separated structure of the poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) triblock copolymer (13 wt % polystyrene (PS) block)
were investigated during mechanical deformation. In situ synchrotron radiation small-angle X-ray scattering (SAXS)/wide-angle
X-ray scattering (WAXS) measurements were successfully performed for
SEBS under equi-biaxial deformation as well as under uniaxial deformation. In situ SAXS/WAXS measurements revealed changes in (1) the
shape of spherical PS domains, (2) the spacing of PS domains packed
in the body-centered cubic structure in the initial state, (3) their
ordering, and (4) the orientation of PEB chains during deformations.
In terms of the microdomain structure, affine deformation was kept
below a certain strain (εd‑A), which are 4
and 1.2 for uniaxial and equi-biaxial deformation, respectively. In
contrast, the ordering of the arranged PS domains decreased from the
initial strain region. Above the εd‑A value,
deviation from affine deformation started to occur. This deviation
is related to contact of PS domains under mechanical deformation.
Uniaxial stretching still showed the plane-independent behavior, while
equi-biaxial stretching did not. Moreover, the εd‑A value for equi-biaxial deformation was smaller than that for uniaxial
deformation and further smaller than expected. This might be because
the entanglement effect was enhanced for equi-biaxial deformation.
Furthermore, after contact of PS domains at around strains of 6 and
2, during uniaxial and equi-biaxial deformation, respectively, the
ordering of PS domains suddenly increased with an increase in strain.
It is inferred that the locked state between the PS domains and the
extended PEB chains formed during deformation may have been released
and repacked at a certain strain.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.