Macromolecules,
Год журнала:
2023,
Номер
56(19), С. 8080 - 8093
Опубликована: Сен. 29, 2023
Vitrimers
are
associative
covalent
adaptable
networks
that
undergo
reversible
bond-exchange
reactions
while
maintaining
a
fixed
cross-linking
density
with
changing
temperature.
To
date,
experimental
studies
rely
on
macroscopic
rheology
have
not
been
able
to
reveal
topological
changes
and
microscopic
dynamics
in
these
materials.
Here,
coarse-grained
molecular
simulations
combined
Monte
Carlo
method
implemented
investigate
the
structural
changes,
dynamics,
linear
of
unentangled
side-chain-linked
vitrimers
conjunction
sticky
Rouse
model
(SRM).
We
find
there
is
minor
variation
structure
The
dynamic
heterogeneities
behavior
system
increase
remarkably
when
approaching
freezing
transition
temperature
Tv.
Quantitative
agreement
between
simulation
results
SRM
predictions
observed
for
stress
relaxation,
elastic
loss
moduli,
relative
mean-squared
displacement,
especially
at
intermediate-
long-time
or
low-frequency
regimes,
where
time–temperature
superposition
principle
satisfied.
obtain
scaling
collapse
curve
bond
relaxation
time,
zero-shear
viscosity,
horizontal
shift
factors
without
introducing
any
parameters,
suggesting
exhibit
similar
even
presence
loop
defects.
Moreover,
good
those
predicted
by
SRM,
indicating
fast
rate
can
be
analyzed
via
single-chain
approach
based
SRM.
Polymer Chemistry,
Год журнала:
2023,
Номер
14(6), С. 680 - 686
Опубликована: Янв. 1, 2023
True
effects
of
internal
tertiary
amines
on
disulfide
exchange
in
cross-linked
networks
are
explored,
which
provides
the
knowledge
for
creation
functional
materials
with
efficient
bond
properties.
Nature Communications,
Год журнала:
2023,
Номер
14(1)
Опубликована: Ноя. 20, 2023
Multiple
relaxation
times
are
used
to
capture
the
numerous
stress
modes
found
in
bulk
polymer
melts.
Herein,
inverse
vulcanization
is
synthesize
high
sulfur
content
(≥50
wt%)
polymers
that
only
need
a
single
time
describe
their
relaxation.
The
S-S
bonds
these
organopolysulfides
undergo
dissociative
bond
exchange
when
exposed
elevated
temperatures,
making
dominate
Through
introduction
of
dimeric
norbornadiene
crosslinker
improves
thermomechanical
properties,
we
show
it
possible
for
Maxwell
model
viscoelasticity
both
covalent
adaptable
networks
and
living
polymers,
which
one
few
experimental
realizations
Maxwellian
material.
Rheological
master
curves
utilizing
time-temperature
superposition
were
constructed
using
as
nonarbitrary
horizontal
shift
factors.
Despite
advances
vulcanization,
this
first
complete
characterization
rheological
properties
class
unique
polymeric
Macromolecules,
Год журнала:
2024,
Номер
57(6), С. 2756 - 2772
Опубликована: Март 6, 2024
Reactive
processing
provides
a
simple
approach
for
grafting
dynamic
covalent
cross-linkers
onto
linear
or
branched
polymers,
resulting
in
adaptable
networks
(CANs).
We
synthesized
poly(n-hexyl
methacrylate)
(PHMA)
CANs
from
neat,
entangled
PHMA
using
radical-based
reactive
to
graft
the
cross-linker
called
BiTEMPS
methacrylate
(BTMA)
between
side
chains.
By
tuning
BTMA
loading,
we
achieved
range
of
cross-link
densities
and
characterized
how
stress
relaxation,
elevated-temperature
creep,
reprocessability
are
affected
by
density.
The
cross-links
chains
allowed
novel
comparison
our
reversible,
polymers
described
sticky
reptation
theory,
which
long-time
relaxation
occurs
unraveling
backbone
entanglements,
process
enabled
dissociation
subsequent
exchange
side-chain
"stickers."
observed
two
regimes
that
required
their
fitting
combination
stretched
exponential
decay
functions
extract
pertinent
parameters.
apparent
activation
energies
creep
viscosity
same
within
experimental
uncertainty
these
CANs,
verifying
shared
mechanisms
governing
temperature
dependence
viscoelastic
responses,
independent
CAN
Notably,
made
linking
∼50–60%
those
reported
previously
with
chain
backbones.
These
outcomes
demonstrate
importance
synthesis-structure-property-reprocessing
relationships
may
be
various
methods
varying
position
incorporation
structure.
Macromolecules,
Год журнала:
2023,
Номер
56(17), С. 6806 - 6817
Опубликована: Авг. 16, 2023
A
vitrimer
has
covalent
cross-links
that
preserve
network
connectivity
but
permit
topology
fluctuations
through
dynamic
exchange
reactions.
In
this
work,
we
investigate
the
linear
rheology
of
polybutadiene
(PB)
vitrimers
bearing
via
dioxaborolane
metathesis.
PB
are
cross-linked
in
solution
using
photoinitiated
thiol-ene
click
chemistry.
As
targeted
cross-link
density
is
increased,
both
insoluble
fraction
and
glass-transition
temperature
increase.
Linear
viscoelasticity
studied
a
combination
small-amplitude
oscillatory
shear
(SAOS),
creep,
stress
relaxation
measurements.
SAOS,
elastic
modulus
approximately
constant
while
viscous
increases
as
angular
frequency
decreases.
compliance
displays
power
law
behavior
persists
for
at
least
8
h.
relaxation,
transitions
from
rubbery
plateau
into
regime.
Both
SAOS
creep
data
visually
superposed
master
curves
horizontal
shift
factors
exhibit
Arrhenius
behavior.
However,
application
these
determined
to
fails
align
single
curve.
(aSAOS)
collapse
short-time
data,
their
activation
energy
(EaSAOS)
matches
effective
Williams–Landel–Ferry
homopolymer,
indicating
dynamics
correspond
strand
segment
relaxations.
Creep
(acreep)
long-time
(Eacreep)
significantly
larger
than
energies
predicted
by
established
theoretical
models
transient
networks.
We
speculate
discrepancy
between
experiment
theory
due
dependence
cross-linker
mobility
within
matrix,
which
not
fully
captured
models.
ACS Applied Materials & Interfaces,
Год журнала:
2023,
Номер
15(21), С. 25212 - 25223
Опубликована: Март 8, 2023
Thermoset
materials
sacrifice
recyclability
and
reshapeability
for
increased
chemical
mechanical
robustness
because
of
an
immobilized,
cross-linked
polymeric
matrix.
The
robust
material
properties
thermosets
make
them
well-suited
applications
such
as
heat-shielding
(HSMs)
or
ablatives
where
excellent
thermal
stability,
good
strength,
high
charring
ability
are
paramount.
Many
these
characteristic
covalent
adaptable
networks
(CANs),
the
static
connectivity
has
been
replaced
with
dynamic
cross-links.
This
allows
network
mobility
while
retaining
cross-link
to
permit
damage
repair
reshaping
that
traditionally
inaccessible
thermoset
materials.
Herein,
we
report
synthesis
hybrid
inorganic–organic
enaminone
vitrimers
contain
exceptionally
weight
percent
polyhedral
oligomeric
silsesquioxane
(POSS)-derivatives.
Polycondensation
β-ketoester-containing
POSS
various
diamine
cross-linkers
led
facile
tunability,
shapeability,
predictable
glass
transition
temperatures,
residual
char
mass
following
degradation.
Furthermore,
show
notable
retention
their
preordained
shape
decomposition,
suggesting
future
utility
in
design
HSMs
complex
detailing.
Macromolecules,
Год журнала:
2024,
Номер
57(4), С. 1788 - 1794
Опубликована: Фев. 13, 2024
Developing
novel
olefin
thermoplastic
elastomers
(TPE-Os)
that
outperform
those
with
well-defined
block
or
grafted
chain
structures
is
both
highly
attractive
and
challenging.
Here,
we
report
the
preparation
of
high-performance
TPE-Os
in
a
combinatorial
way.
Semicrystalline
ethylene/1-octene/diene
copolymers
pendant
vinyl
groups
crystalline
polyethylene
macromers
terminal
double
bonds
are
synthesized,
they
dynamically
linked
dithiol-based
cross-linker
containing
boronic
ester
bond
to
form
new
TPE-O.
Due
synergy
between
physical
crystallization
dynamic
cross-linking,
it
exhibits
significantly
increased
Young's
modulus
(E),
elongation
at
break
(ε),
ultimate
strength
(σ),
tensile
toughness
(UT)
up
27.2
±
3.8
MPa,
902
28%,
26.7
1.1
120.1
9.5
MJ·m–3,
respectively,
which
among
highest
levels
cross-linked
traditional
TPE-Os.
It
also
has
good
elasticity
10-cycle
elastic
recovery
ratio
71.4%;
high
melting
point
nearly
123.8
°C
σ
can
even
maintain
0.14–0.42
MPa
200
°C.
The
TPE-O
offers
reprocessing
performance
113.2%
for
E,
98.5%
ε,
95.8%
σ,
92.5%
UT.
We
believe
our
study
will
facilitate
development
next-generation
higher
performance.
ACS Polymers Au,
Год журнала:
2022,
Номер
2(5), С. 299 - 312
Опубликована: Июль 22, 2022
The
small
specific
entropy
of
mixing
high
molecular
weight
polymers
implies
that
most
blends
dissimilar
are
immiscible
with
poor
physical
properties.
Historically,
a
wide
range
compatibilization
strategies
have
been
pursued,
including
the
addition
copolymers
or
emulsifiers
installing
complementary
reactive
groups
can
promote
in
situ
formation
block
graft
during
blending
operations.
Typically,
such
exploits
reversible
irreversible
covalent
hydrogen
bonds
to
produce
desired
copolymer,
but
there
other
options.
Here,
we
argue
ionic
and
electrostatic
correlations
represent
an
underutilized
tool
for
polymer
tailoring
materials
applications
ranging
from
sustainable
alloys
organic
electronics
solid
electrolytes.
theoretical
basis
is
surveyed
placed
context
existing
experimental
literature
emerging
classes
functional
materials.
We
conclude
perspective
on
how
interactions
might
be
exploited
plastic
waste
upcycling.
