Polymer Testing,
Journal Year:
2022,
Volume and Issue:
118, P. 107877 - 107877
Published: Nov. 24, 2022
Vitrimers
are
an
exciting
class
and
new
generation
of
polymer
materials
combining
the
strength
a
traditional
thermoset
with
reprocessability
thermoplastic
polymer.
However,
key
debate
in
literature
has
surrounded
best
method
to
identify
vitrimer
topology
freezing
temperature
(Tv),
above
which
dynamic
covalent
bond
exchange
reactions
occur,
allowing
for
self-healing,
recycling,
shape
reconfigurability
vitrimers.
While
common
methods
Tv
include
stress
relaxation,
creep,
fluorescence,
we
herein
validate
thermomechanical
analysis
(TMA)
as
reliable
identification.
TMA
provides
several
clear
advantages
it
is
less
time
sample
intensive
than
relaxation.
Furthermore,
performed
compression
match
application
conditions,
more
consistent
results
identifies
coefficient
thermal
expansion
(α).
We
demonstrate
that
valuable
tool
identification
by
validating
clearly
accepted
trends
literature;
validates
increases
decreasing
catalyst
concentration
increasing
heating
rate
while
showing
negligible
variation
applied
force.
Finally,
report
α
our
material.
By
taking
advantage
such
fast
Tv,
believe
this
fundamental
study
will
support
future
research.
ACS Sustainable Chemistry & Engineering,
Journal Year:
2023,
Volume and Issue:
11(30), P. 11077 - 11087
Published: July 18, 2023
Dynamic
covalent
polymer
networks
represent
new
opportunities
in
the
design
of
sustainable
epoxy
resins
due
to
their
excellent
malleability
and
reprocessability;
however,
adaptable
network
is
usually
accompanied
by
low
glass
transition
temperature,
poor
creep
resistance,
mechanical
brittleness.
Herein,
we
demonstrate
a
vanillin-based
hyperbranched
resin
(VEHBP)
containing
disulfide
imine
dynamic
bonds
for
recyclable
malleable
with
high
temperature
(Tg),
significantly
improved
properties.
The
5%VEHBP
exhibited
175
°C
130
34.1,
19.7,
173.3%
increase
tensile
strength,
storage
modulus,
toughness
respectively,
compared
neat
resin.
Meanwhile,
topological
structure
VEHBP
complemented
dual
endowed
these
materials
self-healing
ability,
reprocessability,
degradability,
which
represents
an
important
step
toward
fabrication
high-performance
networks.
Advanced Materials,
Journal Year:
2022,
Volume and Issue:
35(11)
Published: Dec. 23, 2022
The
rapid
increase
in
demand
for
recyclable
and
reusable
thermosets
has
necessitated
the
development
of
materials
with
chemical
structures
that
exhibit
these
features.
Thus,
functional
mesogenic
epoxide
monomers
bearing
both
ester
imine
groups
can
be
vitrimerized
recycled
are
reported
herein.
compounds
show
mesophase
characteristics
at
100-200
°C
converted
into
hard
epoxides
by
a
common
curing
reaction.
obtained
have
high
isotropic
thermal
conductivity
(≈0.64
W
m-1
K-1
),
which
is
derived
from
their
highly
ordered
microstructures.
cured
products
easily
reprocessed
through
metathesis
transesterification,
decomposed
hydrolysis
under
acidic
or
basic
conditions
subsequently
re-cured.
Surprisingly,
repeatedly
chemically
decomposed.
retain
properties
pristine
counterparts,
preserve
advantages
without
alteration
to
any
unique
properties.
A
dehydration
reaction
occurs
between
residual
hydroxyl
during
re-hardening,
dramatically
increases
glass
transition
temperature
≈60
°C.
These
reprocessable
vitrimers
demonstrate
effectiveness
environmental
friendliness
molecular
design
strategy
Macromolecules,
Journal Year:
2023,
Volume and Issue:
56(19), P. 8080 - 8093
Published: Sept. 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.
Macromolecules,
Journal Year:
2024,
Volume and Issue:
57(7), P. 3242 - 3257
Published: March 28, 2024
We
formulate
a
statistical
mechanical
theory
for
how
dynamic
bond
exchange
influences
the
activated
hopping-driven
relaxation
of
Kuhn
segments
in
dynamically
cross-linked
networks
or
vitrimers
over
wide
range
temperatures
and
cross-link
densities.
The
key
new
methodological
aspect
is
to
address
self-consistent
manner
consequences
on
segmental
alpha
relaxation,
vice
versa.
predicted
temperature
dependence
time
at
high
remains
same
as
that
permanent
networks,
but
lower
temperatures,
significant
acceleration
occurs
due
exchanges.
From
mechanistic
perspective,
vitrimer
local
cage
barrier
very
weakly
affected
by
exchange,
while
collective
elastic
contribution
decreases
significantly
deeply
supercooled
regime.
glass
transition
grow
linearly
with
square
root
density,
previously
found
networks.
Material-specific
chemical
effects
such
cross-linker
size
relative
normal
segment
special
attraction
polymers
are
crudely
considered
based
model
calculations.
quantitatively
applied
recent
experiments
dry
ethylene
vitrimers.
Good
agreements
including
follows
an
Arrhenius
law
enough
upward
non-Arrhenius
deviations
emerge
regime,
collapsed
master
curve
exists
densities
temperatures.
Possible
extensions
treat
heterogeneity
penetrant
transport
briefly
discussed.
Advanced Materials,
Journal Year:
2024,
Volume and Issue:
unknown
Published: June 25, 2024
Thermochromic
materials
are
substances
that
change
color
in
response
to
temperature
variations.
Today,
sustainability
concerns
the
main
drivers
of
thermochromic
research,
with
smart,
energy-efficient
windows
being
one
primary
applications.
While
vanadium
oxides
and
leuco
dyes
traditionally
materials,
hydrogels
operating
based
on
solvation
have
risen
as
some
most
promising
due
their
high
optical
transparency
good
solar
modulating
abilities.
In
this
work,
a
distinct
mechanism
for
thermochromism
arising
from
crystalline
solid
amorphous
polymer
transition,
corresponding
transition
an
opaque
state
transparent
is
disclosed.
Both
ultra-high
(T
Macromolecules,
Journal Year:
2025,
Volume and Issue:
unknown
Published: Jan. 8, 2025
Vitrimer,
a
class
of
covalent
dynamic
networks,
is
promising
for
polymeric
applications
requiring
reshaping,
recycling,
and
self-healing.
The
bonds
in
vitrimer
can
be
reversibly
broken
reformed
under
thermal
actuation.
This
work
investigates
the
effects
temperature
on
fracture
toughness
soft
epoxy
vitrimers.
We
measured
above
topology
freezing
temperature.
Elevated
temperatures
reduce
both
stretch
toughness,
while
they
linearly
increase
modulus.
Given
invariant
cross-linking
density,
dependence
attributed
to
sensitivity
bond-exchange
reactions.
extend
Lake–Thomas
theory
by
incorporating
kinetic
bond
scission
elucidate
such
Unlike
conventional
elastomers
with
threshold
decreased
at
elevated
temperatures,
our
indicates
continuous
decrease
until
approximating
zero
value,
aligning
unique
viscous
behavior
