查看更多>>摘要：Owing to the significant increase in air pollutants and the spread of infectious diseases,it seems that the use of face masks will be-come an essential item in human societies.Therefore,there is a need to conduct more research to develop novel types of respirators utilizing up-to-date science such as nanotechnology.In this study,we fabricated a nanocomposite fibrous filter containing modified graphene oxide(GO)and zinc oxide(ZnO)nanoparticles.This layer was used as an active filter for absorbing and removing air pollutants,such as suspended sub-micron particles(below 2.5 microns)and CO2,NO2,and SO2 gases.The synthesized nanostructures and fibrous filters were characterized by differ-ent analysis(FTIR,XRD,TGA,and FESEM),and the performance of the filters was surveyed by tests such as pressure drop,CO2,NO2,SO2 gas rejec-tion,and particulate removal.The results showed that the stabilization of the modified GO and ZnO nanostructures on the fibrous filter improved the effectiveness of this filter as a mask for removing toxic particles and gases,and the filter containing nanoparticles had the best performance.
查看更多>>摘要：As a type of bi-functional device,electrochromic supercapacitors(EC-SCs)have attracted extensive attention in diverse applications such as flexible electronics.However,despite recent encouraging progress,rational design and development of high-performance EC-SC materi-als with desirable stability remain challenging for practical applications.Here,we propose a fluorination strategy to develop high-performance EC-SC materials with tough hydrogen bonding cross-linked intermolecular polymer network by one-step electrosynthesis of 3-fluorothiophene.The electrosynthesized free-standing poly(3-fluorothiophene)(PFT)films simultaneously achieve high electrochromic performance(optical con-trast 42％at 560 nm with reversible color changes between purple and blue),and good capacitance property(290 F·g-1,1 A·g-1),as well as out-standing cyclic stability(＜2％reduction after 20000 cycles).We further demonstrate the fabrication of PFT-based flexible electrochromic superca-pacitor devices(FESDs),and the resultant devices can be used to visually monitor the energy storage state in real-time and maintain outstanding stability under mechanical distortion like bending.Such a tough fluorination hydrogen bonding cross-linking strategy may provide a new design concept for high-performance EC-SC materials and reliable FESDs toward practical applications.
查看更多>>摘要：To realize single-stimulus-induced simultaneous multi-behaviors in hydrogels is still quite challenging nowadays.Herein,an intelli-gent pH-responsive hydrogel(BP4VA/PAS)with rapid and high contrast changes in color,fluorescence,and shape simultaneously is reported.The BP4VA/PAS hydrogel is fabricated by incorporating styryl anthracene derivative(BP4VA)into copolymer networks(PAS)of acrylamide and sodium 4-styrene sulfonate.Under acid conditions,the protonation of BP4VA generates a rapid change with high color contrast from yellow to red and a fluorescence switch between bright green and weak red emission.At the same time,the electrostatic interactions between 2H-BP4VA2+and sulfonate anions suspended on PAS trigger BP4VA/PAS hydrogels to shrink.Upon alkaline treatment,the 2H-BP4VA2+/PAS hydrogel deproto-nates and recovers to its original color,fluorescence,and shape.Furthermore,utilizing rapid and remarkable pH-responsive properties of BP4VA/PAS hydrogels,we successfully demonstrated its applications in biomimicry,camouflage,and multistage information encryption.Collec-tively,this work provided an elegant strategy to develop intelligent hydrogels in applications of biomimetic smart materials and information en-cryption.
查看更多>>摘要：Electrospun nanofibrous separators,despite lacking superior mechanical strength,have gained widespread attention with high poros-ity and facile processing.Herein,utilizing the fact that thermal imidization temperature of poly(amic acid)(PAA)into polyimide(PI)coincides with the pre-oxidation temperature of polyacrylonitrile(PAN)into carbon fiber,we proposed a new cross-electrospinning strategy to obtain a com-posite nanofibrous separator(PI/oPAN)randomly interwoven by PI and pre-oxidized PAN(oPAN)nanofibers,via synchronously electrospinning the PAA and PAN onto the same collector and then heat-treating for 2 h at 300 ℃.The resultant PI/oPAN separator was able to preserve high porosity(71.7％),electrolyte wettability and thermal stability of PI nanofibrous membrane,and surprisingly exhibited high mechanical strength,being 3 times of PI,which mainly because of the numerous adhesion points generated by the melting of PAN in the pre-oxidation process.Mean-while,the polar groups of oPAN and 3D fibrous network enhanced the PI/oPAN separator's ionic conductivity and Li+transference number,ren-dering the corresponding cell with more stable cycling performance than cells assembled with pure PI,PAN or commercial PP separator.There-fore,this work might provide a new avenue for the ongoing design and further development of LIB separators capable of high safety and high performance.
查看更多>>摘要：The crystallization behavior of silica-filled polydimethylsiloxane(PDMS)was investigated in detail by 1H solid-state nuclear magnetic resonance(1 H SS-NMR)in combination with synchrotron radiation wide-angle X-ray scattering(WAXS),and temperature-modulated differential scanning calorimetry(TMDSC)techniques.For neat PDMS,no apparent difference is observed for the crystallinity characterized by 1H SS-NMR and WAXS at low-temperature regions.However,upon filler addition,a 15％-35％lower difference in crystallinity is observed measured by1H SS-NMR compared to WAXS.The origin of such mismatch was explored through multi-component structural,dynamics,and chain-order analysis of PDMS samples with different filler fractions.The 1D integrated WAXS results of PDMS with different filler fractions at different temperatures show that the packing structure as well as crystal size basically remain unchanged,but as the filler fraction increases from 0 phr to 60 phr,the rigid com-ponent's dynamics order parameter Sr obtained by 1H SS-NMR decreases from 0.70 to 0.55.The filler fraction-dependent crystallinity calculated based on Sr was compared with experimental values,revealing a behavior of decreasing order in the crystalline region.Combining with the re-sults of accelerated chain dynamics in crystalline region as reflected by T2 values,the molecular origin is attributed to the formation of CONDIS crystals,whose conformational order is lost but the position and orientation orders are kept.Such hypothesis is further supported by the TMDSC results,where,as the filler fraction increases from 0 phr to 60 phr,the melting range widens from 8.77 K to 14.56 K,representing a growth of 166％.In addition to previous reports related to the condition for forming CONDIS mesophase,i.e.,temperature,pressure,and stretching,the nano-sized filler could also introduce the local conformational disorder for chain packing.
查看更多>>摘要：Nowadays organosilicon luminescent materials are of increasing interest due to the variety of their synthetic or modification tech-niques and application fields.Ladder polyphenylsilsesquioxanes(L-PPSQ)are a unique class of organosilicon polymers,which can be ideal matri-ces for the luminescent composites due to their high thermal stability,optical transparency and mechanical strength.In this work,new mechani-cally strong,heat-resistant,transparent and sensitive to ammonia vapor luminescent composite films based on L-PPSQ have been obtained.As the source of Europium ions oligophenyleuropiumsiloxane was used,demonstrating perfect compatibility to the matrix due to the similar nature.To improve luminescent properties of the films,new organosilicon ligands were introduced into the composites and their influence on the prop-erties of the materials was studied.Valuable properties of described composites may allow their further application as multifunctional coatings.
查看更多>>摘要：The effect of temperature on the electrical conductivity(a)and Seebeck coefficient(S)of n-type vapor grown carbon nanofibers(CNFs)and poly(vinylidene fluoride)(PVDF)melt-mixed with 15 wt％of those CNFs is analyzed.At 40 ℃,the CNFs show stable n-type character(S=-4.8μV·K-1)with an σof ca.165 S·m-1,while the PVDF/CNF composite film shows an σ of ca·9 S·m-1 and near-zero S(S=-0.5 μV·K-1).This experimental reduction in S is studied by the density functional tight binding(DFTB)method revealing a contact electron transfer from the CNFs to the PVDF in the interface.Moreover,in the temperature range from 40 ℃ to 100 ℃,the σ(T)of the CNFs and PVDF/CNF film,successfully described by the 3D variable range hopping(VRH)model,is explained as consequence of a thermally activated backscattering mechanism.On the contrary,the S(T)from 40 ℃ to 100 ℃ of the PVDF/CNF film,which satisfactorily matches the model proposed for some multi-walled carbon nanotube(MWCNT)doped mats;however,it does not follow the increase in S(T)found for CNFs.All these findings are presented with the aim of discerning the role of these n-type vapor grown carbon nanofibers on the σ and S of their melt-mixed polymer composites.
查看更多>>摘要：This study utilizes molecular dynamics simulation to investigate the complex dynamics of entangled semi-flexible polymer melts.The investigation reveals a significant stress overshoot phenomenon in the systems,demonstrating the intricate interplay between shear rates,chain orientation,and chain stretching dynamics.Additionally,the identification of metastable states,characterized by a dual-plateau phenomenon in the shear stress-strain curve at specific Rouse-Weissenberg number WiR,showcases the system's responsiveness to external perturbations and its transition to stable shear banding states.Moreover,the analysis of flow field deviations uncovers a progression of shear bands with increasing WiR,displaying distinct behaviors in the system's dynamics under different shear rates and chain lengths.These findings challenge established theoretical frameworks and advocate for refined modelling approaches in polymer rheology research.
查看更多>>摘要：Polyimide(PI)is widely used in high-frequency communication technology due to its exceptional comprehensive properties.Howev-er,traditional PI has a relatively elevated dielectric constant and dielectric loss.Herein,the different cross-linked structures were introduced in PI matrix and conducted a detailed discussion on the influence of cross-linking agent content and cross-linking structure type on the overall perfor-mance of PI films.In comparison to the dielectric constant of 2.9 of neat PI,PI with an interchain cross-linking structure containing 2 wt％1,3,5-tris(4-aminophenyl)benzene(TAPB)(interchain-PI-2)exhibited the reduced dielectric constant of 2.55 at 1 MHz.The PI films with intrachain cross-linking structure containing 2 wt％TAPB(intrachain-PI-2)exhibited the lowest dielectric constant of 2.35 and the minimum dielectric loss of 0.0075 at 1 MHz.It was due to the more entanglement junctions of intrachain-PI resulting in decreased carrier transport.The thermal expansion coefficients of both interchain-PI and intrachain-PI films were effectively reduced.Moreover,in contrast to interchain-PI films,the intrachain-PI films maintained colorlessness and transparency as the cross-linking agent content increased.This work compared the effects of two different cross-linked structures on the performance of PI films and provided a feasible way to obtain low-k PI films with excellent comprehensive perfor-mance for 5G applications.
查看更多>>摘要：Crosslinking natural rubber(NR)and styrene butadiene rubber(SBR)composites with carbon black(CB)have been utilized in the tire tread industry.A sulfur-based lightly crosslinker can potentially enhance the self-healing capabilities of rubber.Moreover,the rubber composites were studied for non-covalent interactions between the benzene rings of SBR and CB.In this research,rubber samples were prepared,and their structure was investigated using Fourier transform infrared(FTIR),and Raman spectroscopy.The red shift in Raman spectroscopy confirmed non-covalent interaction or hydrophobic interaction between SBR and CB in NR/SBR composites exposed to CB due to environmental change.The dif-ferential scanning calorimetry(DSC)thermograms showed that NR and SBR were incompatible.Additionally,the mechanical properties of these rubber blends were enhanced as the proportion of NR increased.The maximum self-healing performance reached 40％for the formulation con-taining 25 phr NR and 75 phr SBR,which also saved energy with low chain end movements.Therefore,these composites could be utilized as a se-mi-empirical model for studying crosslinked rubber blends,specifically in the rubber tire industry.
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