ChemistrySelect,
Journal Year:
2024,
Volume and Issue:
9(40)
Published: Oct. 1, 2024
Abstract
Polymerization
of
benzoxazine
at
low
temperatures
is
important
because
the
high‐temperature
polymerization
restricts
its
utilization
in
a
wide
range
applications,
though
polybenzoxazines
possess
excellent
properties.
The
effect
nitro
functionality
and
various
substituents
on
thermal
curing
flame‐retardant
behavior
are
mainly
focused
this
study.
In
present
work,
2,2′‐methylenebis(4‐nitrophenol)
(NBP)
was
synthesized
from
4‐nitrophenol
used
for
synthesis
derivatives
with
five
structurally
different
aromatic
amines.
As
contains
nitro‐groups
phenolic
part
substituted
functional
groups
positions
amine
part,
significantly
varied
among
each
other.
ring‐opening
(ROP)
studied
exotherms
DSC
thermogram.
4‐fluoroaniline
2‐aminobenzotrifluoride‐based
benzoxazines
show
highest
lowest
272
189
°C,
respectively,
which
based
their
position
that
can
act
as
an
internal
catalyst.
resulting
higher
char
yield
(49%
≤
63%)
values
LOI
(37
43)
including
flame
retardant
(UL94‐V0)
behaviors
suggesting
polybenzoxazine
be
coatings
high‐performance
industrial
applications.
Small,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Oct. 11, 2024
Abstract
Reversible
and
recyclable
thermosets
have
garnered
increasing
attention
for
their
smart
functionality
sustainability.
However,
they
still
face
challenges
in
balancing
comprehensive
performance
dynamic
features.
Herein,
silicon
(Si)─oxygen
(O)
imidazole
units
covalent
bonds
are
coupled
to
generate
a
new
class
of
bio‐polyimines
(Bio‐Si‐PABZs),
endow
them
with
high
excellent
reprocessing
capability
acid‐degradability.
By
tailoring
the
molar
content
diamines,
this
Bio‐Si‐PABZs
displayed
both
markedly
glass
transition
temperature
(162
°C)
char
yield
at
800
°C
an
oxygen
atmosphere
(73.1%).
These
favorable
properties
outperformed
various
previously
reported
polyimines
competed
effectively
commercial
fossil‐based
polycarbonate.
Moreover,
scratch
(≈10
µ
m)
on
surface
samples
can
be
self‐healing
within
only
2
min,
effective
“
Bird
Nest
”‐to‐“
Torch
”
recycling
also
achieved
through
free
amines
solution.
Most
importantly,
bio‐based
siloxane
adhesive
derived
from
intermediate
Bio‐Si‐PABZ‐1
by
acidic
degradation
demonstrated
broad
robust
adhesion
substrates,
values
reaching
up
≈3.5
MPa.
For
first
time,
study
lays
scientific
groundwork
designing
polyimine
Si─O
units,
as
well
converting
plastic
wastes
into
thermal‐reversibility
renewable
adhesives.
Macromolecules,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Dec. 20, 2024
Herein,
we
synthesized
a
difunctionalized
bio-based
vanillin
azine
monomer
(4,4′-((1E,1′E)-hydrazine-1,2-diylidenebis(methaneylylidene))bis(2-methoxyphenol),
VBAZ-2OH)
via
Schiff
base
reaction
between
and
hydrazine
monohydride.
Subsequently,
successfully
prepared
2,2′-(((1E,1′E)-hydrazine-1,2-diylidenebis(methaneylylidene))bis(8-methoxy-2H-benzo[e][1,3]oxazine-6,3(4H)-diyl))bis(ethan-1-ol),
VBAZ-BZ-2OH),
which
contains
oxazine
units,
through
Mannich
condensation
of
VBAZ-2OH
with
ethanolamine
paraformaldehyde
in
1,4-dioxane
as
the
solvent.
The
chemical
structures
these
two
monomers
(VBAZ-2OH
VBAZ-BZ-2OH)
were
characterized
by
using
NMR
FTIR
analyses.
Our
study
aimed
to
investigate
transesterification
reactions
blending
different
VBAZ-BZ-2OH/phenolic
resin
(BP)
compositions
PEO112-b-PCL99
(EC)
diblock
copolymer
form
various
BP/EC
blends.
These
blends
exhibit
competitive
hydrogen-bonding
interaction
phenomena,
analyzed
one-dimensional
two-dimensional
Interestingly,
after
thermal
treatment
at
150
°C,
ordered
self-assembled
lamellae
or
hexagonal
packed
cylinder
transform
into
disordered
micelle
disorder
structure
result
due
EC
becoming
miscible
VBAZ-BZ-2OH
monomer,
disrupting
structure,
was
confirmed
TEM
SAXS
could
easily
understand
order–disorder
morphological
transformation
replace
thermogravimetric
analysis
(TGA)
coupled
microcomputed
gas
chromatography
(TGA-GC)
This
study
explores
the
use
of
chitosan
as
a
sustainable
alternative
in
vitrimerization
thermoset
epoxy
resins.
Epoxy/chitosan
vitrimer
composites,
with
and
without
an
external
catalyst
(zinc
acetate),
well
epoxy/zinc
acetate
vitrimers
reference
samples,
were
successfully
fabricated
through
mechanochemical
ball-milling,
followed
by
hot-pressing.
Comprehensive
multiscale
analyses
conducted,
results
compared
existing
literature.
Incorporating
significantly
enhanced
process,
leading
to
remarkable
improvements
mechanical
performance,
solvent
resistance,
stress
relaxation.
Specifically,
inclusion
15
wt
%
chitosan,
catalyst,
increased
vitrimer's
elastic
modulus
100%
tensile
strength
35%
virgin
resin,
while
reducing
relaxation
time
approximately
800
s,
order
magnitude
lower
than
epoxy/cellulose
reported
Remarkably,
presence
zinc
acetate,
epoxy/chitosan
composites
further
decreased
150
increasing
210%
80%,
respectively,
those
resin.
The
reduction
was
attributed
chitosan's
primary
amine
hydroxyl
groups,
which
facilitated
multiple
exchange
reactions
(transesterification,
ester-to-amide,
transamidation)
acted
self-catalysts
for
transesterification.
Enhancements
properties
zinc-coordinated
interactions
within
polymer
networks.
also
investigates
influence
cross-linking
density
activation
energy
competitive
parameters
on
behavior
glass
transition
temperature
(Tg)
vitrimers.
multiple-dynamic
network
rapid
characteristics
make
them
promising
candidates
variety
applications,
supporting
circular
economy.
work
represents
first
resins,
advancing
development
recyclable
materials.
Organic & Biomolecular Chemistry,
Journal Year:
2025,
Volume and Issue:
23(10), P. 2498 - 2509
Published: Jan. 1, 2025
Dynamic
covalent
macrocycles
offer
the
advantage
of
tunable
ring-opening/ring-closure
and
structural
transformation,
but
their
control
with
precision
remains
a
daunting
task
due
to
labile
nature
reversible
bonds.
Herein
we
demonstrate
precise
formation/scission
varied
sizes
by
contrasting
reactivity,
stability,
degradability
light-active
light-inactive
dynamic
The
incorporation
photoswitchable
non-photoresponsive
aldehyde
sites
into
one
single
dialdehyde
component
afforded
creation
[1
+
1]
type
primary
diamines
suitable
lengths.
manipulation
light
acid/base
stimuli
allowed
on-demand
breaking/remaking
macrocycles,
achieving
interconversion
between
macrocyclic
linear
skeletons.
Moreover,
combination
dialdehyde,
diamines,
secondary
enabled
construction
hetero-type
[2
1
1']
via
enhanced
discrimination
hierarchical
assembly.
Light-induced
kinetic
locking/unlocking
bonds
further
macrocycle-to-macrocycle
conversion
when
needed.
Through
leveraging
controllable
connection/disconnection,
switchable
formation/disintegration
mechanically
interlocked
catenanes
was
accomplished.
results
described
showcase
potential
photoinduced
chemistry
for
preparing
complex
architectures
should
set
stage
molecular
recognition,
assemblies,
synthetic
motors,
responsive
materials.
Silicone
resins,
known
for
their
exceptional
properties
across
various
industries,
are
traditionally
nonreprocessable
due
to
permanent
cross-linked
networks.
Herein,
we
propose
a
method
turn
disadvantage
into
an
advantage
by
converting
silanol
(Si–OH)
groups─adverse
factors
thermal
stability─into
dynamic
Si–O–Ph
bonds,
thereby
endowing
silicone
resin
with
reprocessability.
Polysiloxane
oligomers
benzoxazine
side
groups
(PBTS)
were
formed
via
hydrolysis–condensation
reactions
between
monofunctional
benzoxazine-containing
siloxane
(P-mdes)
monomers
and
triethoxymethylsilane
(MTES).
The
curing
behaviors
of
PBTS
analyzed
using
DSC
FTIR,
confirming
the
formation
resin-based
covalent
adaptive
networks
(CANs)
through
introduction
bonds.
resulting
CANs
exhibit
reprocessability
significantly
improved
mechanical
properties.
tensile
strength
original
reaches
23.34
MPa,
even
after
five
cycles
reprocessing,
remains
at
22.98
demonstrating
excellent
retention.
Tg
Td5
reach
up
132
°C,
424
425
°C
in
nitrogen
or
air
atmospheres,
respectively.
Notably,
reprocessed
samples
maintain
heat
resistance
stability
reprocessing
cycles,
values
around
130
380
°C.
