7 research outputs found
Sequence Features of Sequence-Controlled Polymers Synthesized by 1,1-Diphenylethylene Derivatives with Similar Reactivity during Living Anionic Polymerization
Living anionic polymerization (LAP)
is the primary representative
method of living polymerization and exhibits the ability to synthesize
sequence-regulated functionalized polymers. However, there has always
been a lack of special features for LAP to guide these cutting-edge
syntheses in sequence-controlled polymers. In this study, the copolymerizations
of a series of alkyl-substituted 1,1-diphenylethylene derivatives
(DPE-alkyls), which display similar reactivities but different structures,
and St were performed. In addition, the processes of whole chain propagation
were monitored by the <i>in situ</i> <sup>1</sup>H NMR method.
The results show that changing the alkyl type of DPE-alkyls has little
influence on their sequence distributions during copolymerization.
Therefore, we could deduce a reasonable principle called “sequence
equivalence” in LAP: the copolymers of different DPE derivatives
and St would have identical sequence structures when DPE derivatives
exhibit exactly the same reactivity ratio (<i>r</i><sub>St</sub>) during the copolymerization under the same conditions.
Furthermore, the combination of <i>in situ</i> <sup>1</sup>H NMR experiments and kinetic Monte Carlo model (KMC) simulations
was conducted synchronously. The results of simulations show that
the KMC model not only can simulate detailed information for LAP of
DPE derivative and St but also could quantify the precision of the
corresponding sequence distributions. Additionally, the KMC model
that we constructed for the simulation of sequence control in LAP
can give us a new insight into the possibility of sequence tailoring.
Next, the relationship among the glass transition temperatures (<i>T</i><sub>g</sub>s), types of alkyl substituent, and sequence
structures of DPE derivative units in the chains was investigated.
Through DSC analysis, this study’s results indicated that polymers
with similar sequences but different alkyl substituents present contrasting
differences in thermal property. These results could provide a broader
understanding of the thermal properties of polymers
Biobased Inverse Vulcanized Polymer from Magnolol as a Multifunctional Ingredient for Carbon-Black-Reinforced Rubber Composites
Inverse
vulcanization provides a facile route to transform industrial
byproduct sulfur into attractive polymeric materials with a variety
of applications. Herein, an inverse vulcanized copolymer (PSM) was
synthesized by copolymerization of biomass magnolol and sulfur. PSM
presents outstanding intrinsic flame retardancy by the formation of
a highly pyrolysis-resistant carbonaceous material during combustion.
Especially, it can serve as a multifunctional ingredient when utilized
in rubber composites. The presence of polysulfide segments and biphenol
moieties enables PSM to cross-link rubber effectively and react with
the oxygenic groups on the surface of carbon black (CB), thus resulting
in the improvement of CB dispersion and stronger interfacial interaction
between a rubber matrix and nanofillers than the conventional sulfur-cross-linked
rubber composite. Incorporation of PSM also significantly retards
the thermo-oxidation aging of the composites due to its radical scavenging
capability. Moreover, the dynamic covalent polysulfide segments in
the system confer the PSM-cross-linked rubber material reprocessability
and recyclability
Biobased Inverse Vulcanized Polymer from Magnolol as a Multifunctional Ingredient for Carbon-Black-Reinforced Rubber Composites
Inverse
vulcanization provides a facile route to transform industrial
byproduct sulfur into attractive polymeric materials with a variety
of applications. Herein, an inverse vulcanized copolymer (PSM) was
synthesized by copolymerization of biomass magnolol and sulfur. PSM
presents outstanding intrinsic flame retardancy by the formation of
a highly pyrolysis-resistant carbonaceous material during combustion.
Especially, it can serve as a multifunctional ingredient when utilized
in rubber composites. The presence of polysulfide segments and biphenol
moieties enables PSM to cross-link rubber effectively and react with
the oxygenic groups on the surface of carbon black (CB), thus resulting
in the improvement of CB dispersion and stronger interfacial interaction
between a rubber matrix and nanofillers than the conventional sulfur-cross-linked
rubber composite. Incorporation of PSM also significantly retards
the thermo-oxidation aging of the composites due to its radical scavenging
capability. Moreover, the dynamic covalent polysulfide segments in
the system confer the PSM-cross-linked rubber material reprocessability
and recyclability
Biobased Inverse Vulcanized Polymer from Magnolol as a Multifunctional Ingredient for Carbon-Black-Reinforced Rubber Composites
Inverse
vulcanization provides a facile route to transform industrial
byproduct sulfur into attractive polymeric materials with a variety
of applications. Herein, an inverse vulcanized copolymer (PSM) was
synthesized by copolymerization of biomass magnolol and sulfur. PSM
presents outstanding intrinsic flame retardancy by the formation of
a highly pyrolysis-resistant carbonaceous material during combustion.
Especially, it can serve as a multifunctional ingredient when utilized
in rubber composites. The presence of polysulfide segments and biphenol
moieties enables PSM to cross-link rubber effectively and react with
the oxygenic groups on the surface of carbon black (CB), thus resulting
in the improvement of CB dispersion and stronger interfacial interaction
between a rubber matrix and nanofillers than the conventional sulfur-cross-linked
rubber composite. Incorporation of PSM also significantly retards
the thermo-oxidation aging of the composites due to its radical scavenging
capability. Moreover, the dynamic covalent polysulfide segments in
the system confer the PSM-cross-linked rubber material reprocessability
and recyclability
Assessing the Sequence Specificity in Thermal and Polarized Optical Order of Multiple Sequence-Determined Liquid Crystal Polymers
To
assess the inherent effect of sequence distribution on thermal
and polarized optical order, side-chain liquid crystal polymers (SCLCPs)
with precise side-chain sequence control were synthesized and characterized.
Multiple uniform (M-U), alternating (M-A), gradient (M-G), and interval
(M-I) polymers were conveniently used as well-designed Si–H
functional backbones, and the treatment of these sequence-determined
backbones with mesogenic moieties was conducted via highly efficient
hydrosilylation to obtain sequence-determined SCLCPs with well-designed
molecular compositions and narrow polydispersity index (PDI). The
molecular arrangement of multiple analogous architectures was constructed,
which provided the unique opportunity to comprehensively study how
the sequence impacts liquid crystalline (LC) behavior. The general
trends that the thermal and polarized optical order are significantly
sensitive to sequence specificity in the order M-U > M-A > M-G
> M-I
for a given SCLCPs with a similar number or similar overall concentration
of mesogenic moieties are deduced. Here, SCLCPs with important sequence
control led to increased understanding of interior structure–property
relations owing to the specific spacing between adjacent LC pendants.
As such, this spacing will be recognized as an essential parameter
that determines LC properties that are of interest to be explored
Effect of Topology and Composition on Liquid Crystal Order and Self-Assembly Performances Driven by Asynchronously Controlled Grafting Density
A series of thermo-tunable
liquid crystal block copolymers (LCBCs)
with well-designed architectures were successfully synthesized. Linear/star
polyÂ[4-(4-vinylphenyl)-1-butene]-<i>block</i>-polybutadiene
(PVSt-<i>co</i>-PB) moieties were obtained using living
anionic copolymerization of 4-(4-vinylphenyl)-1-butene with butadiene,
and topological [PVSt-<i>co</i>-PB]-LCBCs were generated
through the adherence of mesogenic moiety via facile hydrosilylation.
The PVSt LC block had well-defined grafting densities of approximately
100%, 70%, and 40%, whereas the PB LC block had an asynchronously
tunable grafting density. This work included comprehensive studies
on their self-assembly and yielded some interesting results. The influences
of topologies and compositions on the phase transition behaviors and
polarized optical performances of the resulting LCBCs that were driven
by asynchronously controlled grafting density were carefully illustrated.
The LCBCs with controlled molecular weight (MW) and narrow PDI showed
wider LC phase ranges (Δ<i>T</i>) and a high tunability
was added into the construction to aid thermos-responsive devices.
The wide Δ<i>T</i> and high thermo-stability were
demonstrated to be complementary between two LC blocks. However, the
response-time and aggregation morphology in POM showed close similarity
to LC blocks and showed a gradient in temperature-dependent changes
with the PB LC block at a lower temperature and the PVSt LC block
at a higher temperature. It is common for LC texture to change with
varying temperature, whereas the gradient switching process was unique
to LC blocks, which was further confirmed by temperature-dependent
WAXD. In particular, the structural reorganization was determined
to be driven by asynchronous grafting density by measuring the temperature-variation
AFM, in that the asynchronous-tunable motion between LC blocks facilitates
small phase separation
Strategies for Tailoring LC-Functionalized Polymer: Probe Contribution of [<i>Si–O–Si</i>] versus [<i>Si–C</i>] Spacer to Thermal and Polarized Optical Performance “Driven by” Well-Designed Grafting Density and Precision in Flexible/Rigid Matrix
A versatile strategy is highly desired
to prepare well-designed
side chain liquid crystal polymers (SCLCPs). Two rigid and topological
SiH/Vinyl-functionalized polystyrenes (PSs), namely polyÂ(4-vinylphenylÂdimethylsilane)
(PVPDMS) and polyÂ(4-vinylÂphenyl-1-butene) (PVSt), were synthesized
via anionic polymerization (AP) and detailed; subsequently, Vinyl/SiH
terminated LCs were treated with PVSt/PVPDMS via hydrosilylation to
yield SCLCPs bearing [<i>Si–O–Si</i>]/[<i>Si–C</i>] spacers. Herein, well-designed grafting density,
evaluated by <sup>1</sup>H NMR, was readily performed by the varying
SiH to Vinyl feed mole ratio. The design systematically probes a cooperative
effect of architectures on properties and allows for precision in
flexible/rigid matrixes. Regardless, PB/PS systems with saturated
addition displayed the best performances. Fundamentally, the study
compared the dependence of polarized optical and thermal performances
on [<i>Si–O–Si</i>] versus [<i>Si–C</i>] spacer, which submitted to be driven by grafting density, providing
the first access to tailoring polymer. SCLCPs exhibited essentially
constant S<sub>m</sub>A, but inconsistent dynamic of spacer-induced
contribution, in which Δ<i>T</i> was the same in complete
addition as if nothing with spacer; surprisingly, followed by decreased
grafting density, the decreasing trend in Δ<i>T</i> of [<i>Si–O–Si</i>] as spacer was fast,
while that of [<i>Si–C</i>] was slow. This phenomenon
was further confirmed by POM. Furthermore, [<i>Si–O–Si</i>] was desired to obtain lower <i>T</i><sub>g</sub> and
applicable to the advantageous “decoupling effect”.
Endeavor for tailoring SCLCPs and regulating devices, the appropriate
spacer and grafting density advanced to an effective role