We report an investigation of the influence of block copolymer architectures on formation of nanophases in epoxy thermosets via reaction-induced microphase separation approach. Toward this end, three ...binary block copolymers composed of polystyrene (PS) and poly(ε-caprolactone) (PCL) were synthesized via the combination of ring-opening polymerization (ROP) and atomic transfer radical polymerization (ATRP). These block copolymers possess PS-b-PCL diblock, PS-b-PCL-b-PS triblock, and PCL-b-PS-b-PCL triblock architectures; they were carefully controlled to have the identical composition and overall molecular weights. It was found that the block copolymers with different architectures in epoxy thermosets displayed quite different reaction-induced microphase separation behavior as evidenced with the results of atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and dynamic mechanical thermal analysis (DMTA). The morphological transition from spherical to cylindrical to lamellar nanophases occurred with increasing the content of the block copolymer in the thermosets containing PS-b-PCL diblock copolymer. In the thermosets containing PS-b-PCL-b-PS triblock copolymer, unilamellar and multilamellar nanophases were formed depending on the content of the triblock copolymer. In contrast, the macroscopic phase separation occurred in the thermosets containing PCL-b-PS-b-PCL triblock copolymer. The behavior of nanophases in these thermosetting blends have been accounted for the demixing behavior of the miscible blocks (viz. PCL) during the reaction-induced microphase separation and the influence of copolymer architectures on the morphologies of PS microdomains.
In this study, we synthesized poly(ethylene oxide)-block-poly(ε-caprolactone)-block-polystyrene (PEO-b-PCL-b-PS) triblock copolymer via the combination of ring-opening polymerization (ROP) and atomic ...transfer radical polymerization (ATRP). The ABC triblock copolymer was incorporated into epoxy to access the nanostructured thermosets. It is found that the nanophases of the epoxy thermosets can be modulated by using different hardeners. While cured with 4,4′-methylenebis(2-chloroaniline), the thermosets displayed the long-ranged ordered nanostructures in which the spherical nanophases were arranged into body-centered cubic (bcc) lattice at the compositions investigated. While 4,4′-diaminodiphenylsulfone was used as the hardener, the thermosets displayed the lamellar nanostructure. The formation of nanostructures in the thermosets has been evidenced by atomic force microscopy and small-angle X-ray scattering. The morphological transition from spherical to lamellar nanophases has been interpreted in terms of the microphase separation of different subchains of the ABC triblock copolymer out of the epoxy–amine matrix during the curing reactions owing to the dependence of miscibility of epoxy networks with PCL subchain of the triblock copolymer on types of hardeners. The kinetics of curing and microphase separation shows the tandem reaction-induced microphase separation occurred while DDS was used as the hardener, which gave rise to the formation of lamellar nanostructures in the epoxy thermosets containing the ABC triblock copolymer.
In this paper, biodegradable epoxidized natural rubber containing cyclic carbonate groups (CNR) was prepared by the reaction between epoxidized natural rubber (ENR) and carbon dioxide. Dynamic ...disulfide bonds and a boronic ester structure were successfully constructed and then the cross-linking network was formed by the thermally initiated "click" reaction between thiol groups of the cross-linker and the residual epoxy groups of ENR. As a result of the exquisite double dynamic covalent structure, the material exhibits high self-healing efficiency. Moreover, by virtue of the cyclic carbonate structure of the CNR, the natural rubber was confirmed to be biodegradable according to the biodegradable measurement. To the best of our knowledge, natural rubber with biodegradable and self-healing characteristics was obtained for the first time.
Microgels have unique and versatile properties allowing their use in forward osmosis areas as a draw agent. In this contribution, poly(4-vinylpyridine) (P4VP) was synthesized via RAFT polymerization ...and then grafted to a poly(
-Isopropylacrylamide) (PNIPAAm) crosslinking network by reverse suspension polymerization. P4VP was successfully obtained by the quasiliving polymerization with the result of nuclear magnetic resonance and gel permeation chromatography characterization. The particle size and particle size distribution of the PNIPAAm-
P4VP microgels containing 0, 5, 10, 15 and 20 wt% P4VP were measured by means of a laser particle size analyzer. It was found that all the microgels were of micrometer scale and the particle size was increased with the P4VP load. Inter/intra-molecular-specific interactions, i.e., hydrogen bond interactions were then investigated by Fourier infrared spectroscopy. In addition, the water flux measurements showed that all the PNIPAAm-
-P4VP microgels can draw water more effectively than a blank PNIPAAm microgel. For the copolymer microgel incorporating 20 wt% P4VP, the water flux was measured to be 7.48 L∙m
∙h
.
Stretchable conductive composites play a pivotal role in the development of personalized electronic devices, electronic skins, and artificial implant devices. This article explores the fabrication ...and characterization of stretchable composites based on natural rubber (NR) filled with molybdenum disilicide (MoSi2) nanoparticles and multi-walled carbon nanotubes (MWCNTs). Experimental characterization and molecular dynamics (MD) simulations are employed to investigate the static and dynamic properties of the composites, including morphology, glass transition temperature (Tg), electrical conductivity, and mechanical behavior. Results show that the addition of MoSi2 nanoparticles enhances the dispersion of MWCNTs within the NR matrix, optimizing the formation of a conductive network. Dynamic mechanical analysis (DMA) confirms the Tg reduction with the addition of MWCNTs and the influence of MoSi2 content on Tg. Mechanical testing reveals that the tensile strength increases with MoSi2 content, with an optimal ratio of 4:1 MoSi2:MWCNTs. Electrical conductivity measurements demonstrate that the MoSi2/MWCNTs/NR composites exhibit enhanced conductivity, reaching optimal values at specific filler ratios. MD simulations further support experimental findings, highlighting the role of MoSi2 in improving dispersion and mechanical properties. Overall, the study elucidates the synergistic effects of nanoparticles and nanotubes in enhancing the properties of stretchable conductive composites.
The need to reach carbon neutrality as soon as possible has made the use of recycled materials widespread. However, the treatment of artificial marble waste powder (AMWP) containing unsaturated ...polyester is a very challenging task. This task can be accomplished by converting AMWP into new plastic composites. Such conversion is a cost-effective and eco-friendly way to recycle industrial waste. However, the lack of mechanical strength in composites and the low filling content of AMWP have been major obstacles to its practical application in structural and technical buildings. In this study, a composite of AMWP/linear low-density polyethylene (LLDPE) filled with a 70 wt% AMWP content was fabricated using maleic anhydride-grafted polyethylene as a compatibilizer (MAPE). The mechanical strength of the prepared composites is excellent (tensile strength ~18.45 MPa, impact strength ~51.6 kJ/m
), making them appropriate as useful building materials. Additionally, laser particle size analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and thermogravimetric analysis were used to examine the effects of maleic anhydride-grafted polyethylene on the mechanical properties of AMWP/LLDPE composites and its mechanism of action. Overall, this study offers a practical method for the low-cost recycling of industrial waste into high-performance composites.
Natural rubber (NR) exhibits good elasticity, flexural resistance, wear resistance, and excellent mechanical properties, and it has been widely used in aerospace, transportation, medical, and health ...fields. For NR, however, the resistance to thermal-oxidation and ozone aging is fairly poor. Although aging properties of NR can be significantly improved with the incorporation of chloroprene rubber (CR) according to some references, the miscibility between NR and CR, the morphologies of the binary blends, and so on are revealed ambiguously. In this work, molecular dynamics simulation (MD) and dissipative particle dynamics (DPD) simulation were carried out to predict the compatibility between natural rubber and chloroprene rubber in view of Flory-Huggins parameters. The morphologies of the blends were obtained with the use of the DPD method. The simulation results were furtherly examined by means of Fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical analysis (DMA). It was found that the miscibility between NR and CR is poor. Nevertheless, the miscibility could be improved when the content of CR is 50% or 90%. In addition, spinodal decomposition with a critical temperature of 390 K would take place according to the phase diagram. Microphase structure such as spherical, lamellar, and bicontinuous phases can be found with different contents of CR in the blends with the results of morphologies analysis.
In this work, the synthesis of 3‐methacryloxypropylheptaphenyl POSS, a new POSS macromer (denoted MA‐POSS) is reported. The POSS macromer is used to synthesize PEO‐b‐P(MA‐POSS)‐b‐PNIPAAm triblock ...copolymers via sequential atom transfer radical polymerization (ATRP). The organic‐inorganic, amphiphilic and thermoresponsive ABC triblock copolymers are characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) and atomic force microscopy (AFM) show that the hybrid ABC triblock copolymers are microphase‐separated in bulk. Cloud point measurements show that the effect of the hydrophiphilic block (i.e. PEO) on the LCSTs is more pronounced than the hydrophobic block (i.e. P(MA‐POSS)). Both transmission electron microscopy (TEM) and dynamic light scattering (DLS) show that all the triblock copolymers can be self‐organized into micellar aggregates in aqueous solutions. The sizes of the micellar aggregates can be modulated by changing the temperature. The temperature‐tunable self‐assembly behavior is interpreted using a combination of the highly hydrophobicity of P(MA‐POSS), the water‐solubility of PEO and the thermoresponsive property of PNIPAAm in the triblock copolymers.
A series of organic‐inorganic triblock copolymers composed of poly(ethylene oxide) (PEO) and poly(N ‐isopropylacrylamide) (PNIPAAm) endblocks and a poly(MA POSS) midblock are synthesized via a sequential atom transfer radical polymerization (ATRP) approach. The PEO‐b‐P(MA POSS)‐b‐PNIPAAm ABC triblock copolymers possess microphase‐separated morphologies. It is found that, in aqueous solutions, the ABC triblock copolymers can display a temperature‐tunable self‐assembly behavior.
The interface plays a decisive role on the performance of nano dielectric composite films, and researchers have made tremendous efforts to confirm the existence of the interface in nano dielectric ...composite films. However, establishing quantitative determining interface information of nano composites is very difficult. In this paper, a typical nano dielectric, PI/SiO2 composite film with content of 10% SiO2 was prepared by an in-situ method and the microstructures of PI/SiO2 and pure PI were obtained by the small-angle X-ray scattering (SAXS), which is a non-destructive testing method. The TEM results show that the average grain diameter of SiO2 particles and the thicknesses of the interfaces are about 7.5 nm and 2.2 nm, respectively. The SAXS results are confirmed by direct TEM imaging method, in which SiO2 particles adsorb the surrounding PI molecular chains, and form the interfaces. The average grain diameters of SiO2 (not including the absorbed PI) particles and the thicknesses of interfaces are about 6.8 nm and 2.6 nm respectively. From this paper, we have proved that SAXS is a new effective means for the quantitative determining of interface information of nano composites.
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Constructing hierarchical structures is indispensable to tuning the electromagnetic properties of carbon-based materials. Here, carbon microtubes with nanometer wall thickness and micrometer diameter ...were fabricated by a feasible approach with economical and sustainable kapok fiber. The carbonized kapok fiber (CKF) exhibits microscale pores from the inherent porous templates as well as pyrolysis-induced nanopores inside the wall, affording the hierarchical carbon microtube with excellent microwave absorbing performance over broad frequency. Particularly, CKF-650 exhibits an optimized reflection loss (RL) of −62.46 dB (10.32 GHz, 2.2 mm), while CKF-600 demonstrates an effective absorption bandwidth (RL < −10 dB) of 6.80 GHz (11.20−18.00 GHz, 2.8 mm). Moreover, more than 90% of the incident electromagnetic wave ranging from 2.88 GHz to 18.00 GHz can be dissipated by simply controlling the carbonization temperature of KF and/or the thickness of the carbon-microtube-based absorber. These encouraging findings provide a facile alternative route to fabricate microwave absorbers with broadband attenuation capacity by utilizing sustainable biomass.
