查看更多>>摘要：In this work,poly(3-hexylthiophene)(P3HT)ultrathin films(P3HT-T)were prepared by spin-coating a dilute P3HT solution(in a toluene:o-dichlorobenzene(Tol:ODCB)blend with a volume ratio of 80∶20)with ultrasonication and the addition of the nucleating agent bicycle[2.2.1]heptane-2,3-dicarboxylic acid disodium salt(HPN-68L)on glass,Si wafers and indium tin oxide(ITO)substrates.The electrical and mechanical properties of the P3HT-T ultrathin films were investigated,and it was found that the conductivity and crack onset strain(COS)were simultaneous-ly improved in comparison with those of the corresponding pristine P3HT film(P3HT-0,without ultrasonication and nucleating agent)on the same substrate,regardless of what substrate was used.Moreover,the conductivity of P3HT-T ultrathin films on different substrates was similar(varying from 3.7 S.cm-1 to 4.4 S·cm-1),yet the COS increased from 97％to 138％by varying the substrate from a Si wafer to ITO.Combining graz-ing-incidence wide-angle X-ray diffraction(GIXRD),UV-visible(UV-Vis)spectroscopy and atomic force microscopy(AFM),we found that the solid order and crystallinity of the P3HT-T ultrathin film on the Si wafer are highest,followed by those on glass,and much lower on ITO.Finally,the sur-face energy and roughness of three substrates were investigated,and it was found that the polar component of the surface energy γP plays a criti-cal role in determining the crystalline microstructures of P3HT ultrathin films on different substrates.Our work indicates that the P3HT ultrathin film can obviously improve the stretchability and simultaneously retain similar electrical performance when a suitable substrate is chosen.These findings offer a new direction for research on stretchable CP ultrathin films to facilitate future practical applications.
查看更多>>摘要：Rubbers or elastomers play an important role in hi-tech technology and civilian daily life because of their unique and strategical prop-erties.Generally,the rubber additives are essential components for rubbers'practical application.Nowadays,developing novel multifunctional additives has attracted increasing research attention.In this work,low-cost crude carbon dots(CCDs)were used as multifunctional additives for natural rubber/silica system(without any additional modification)through industrial compatible melt-mixing method.The results revealed that the CCDs could disperse well in the NR/silica system,and they could not only endow the rubber compound with excellent anti-aging capability due to CCDs'radical scavenging activity because of their plenty of nitrogen-containing species,but also improve the curing rate and mechanical performance of the rubber composite.Also,the CCDs could reduce the rolling resistance of the rubber composites(tano value at 7％strain of the rubber composite could be decreased by 34％),which is promising for the application of energy-saving tire industry.Lastly,the addition of CCDs could effectively reduce the ZnO dosage by at least 40％in the rubber composite without deteriorating its performance.Overall,this work pro-vides valuable guidance to develop novel cheap yet effective additives for the elastomer.
查看更多>>摘要：Non-aromatic fluorescent and multi-responsive materials,exhibiting inherent fluorescence emission and controlled phase change,have garnered significant attention in recent years.However,the underlying interaction between their fluorescent properties and phase transi-tion remains unclear.In this study,we synthesized a series of catalyst-free aza-Michael addition-based polyethyleneimine(RFPEI)materials by re-acting polyethyleneimine(PEI)with N-isopropyl acrylamide(NIPAM).The resulting RFPEI was comprehensively characterized,and demonstrated dual-phase transition behavior(LCST and UCST)in water,which could be finely tuned by adjusting its composition or external factors such as pH.Notably,upon UV irradiation(365 nm),RFPEI exhibited strong fluorescence emission.We further investigated the effects of NIPAM grafting per-centage to PEI,polymer concentration,and pH on the LCST/UCST and fluorescent properties of RFPEI aqueous solutions.Moreover,we show-cased the great potential of RFPEI as a versatile tool for physiological cell imaging,trace detection,and controlled release of doxorubicin.Our study presents a novel class of stimuli-responsive fluorescent materials with promising applications in the field of biomedicine.
查看更多>>摘要：In order to achieve efficient and durable oil-water emulsion separation,the membranes possessing high separation efficiency and me-chanical strength attract extensive attention and are in great demand.In present study,a kind of polytetrafluoroethylene(PTFE)-based bilayer membrane was fabricated by electrospinning fibrous PTFE(fPTFE)on an expanded PTFE(ePTFE)substrate.The morphological observation re-vealed that the fibrous structure of the fPTFE layer could be tailored by controlling the formulation of spinning solution.The addition of appropri-ate polyoxyethylene(PEO)would make the fibers in the fPTFE layer finer and more uniform.As a result,the compounded membrane exhibited a small pore size of approximately 1.25 μm and a substantial porosity nearing 80％.This led to super-hydrophobicity,characterized by a high water contact angle(WCA)of 149.8°,and facilitated rapid oil permeation.The water-in-oil emulsion separation experiment further confirmed that the compounded membrane not only had a high separation efficiency closing 100％,but such an outstanding separation capacity could be largely retained,either through multiple cycles of use or through strong acid(pH=1),strong alkali(pH=12),or high-temperature(100 ℃)treatment.Ad-ditionally,the mechanical behavior of the bilayer membrane was basically contributed by that of each layer in terms of their volume ratio.More significantly,the poor creep resistance of fPTFE layer was suppressed by compounding with ePTFE substrate.Hence,this study has laid the groundwork for a novel approach to create PTFE-based compounded membranes with exceptional overall characteristics,showing promise for applications in the realm of emulsion separation.
查看更多>>摘要：To enhance the mechanical properties of polypropylene random copolymer(PPR),polystyrene(PS)with four different contents were added to the PPR matrix through melt blending.Subsequently,using the Multi-Flow Vibration Injection Molding(MFVIM)technology,PPR/PS in situ microfiber composites(MFC)with different blending ratios were prepared.The results indicated that blending ratio had a great impact on the phase morphology and crystal structure of MFVIM samples,which was different from those of conventional injection molding(CIM)samples.PS ultrafine fibers could be formed under the shear field and could absorb the PPR molecular chains to form hybrid shish-kebab structures.Mean-while,the PPR matrix could also form shish-kebab structures under the effect of strong shear.When the PS content reached 20％,under the com-bined action of PS in situ microfibers and highly oriented crystal structure,the tensile strength and Young's modulus of the sample were obvious-ly improved and the impact strength remained at a relatively high level.So a strong and tough balanced PPR based material was obtained.These results provide valuable insights for expanding the industrial and daily-life applications of PPR and show promising development prospects.
查看更多>>摘要：In this study,flexible and highly conductive composite rubber at low filler content was successfully prepared through polydopamine-assisted electroless silver plating plus mechanical mixing.Firstly,carbon fibers(CF)were activated by polydopamine(PDA)to improve the sur-face activity by self-polymerization reaction.Next,because of the metal chelating ability of PDA,silver layer was firmly deposited on the surface of CF through a facile electroless silver plating method.Finally,flexible silver-plated carbon fibers(Ag/pCF)silicone rubber composites prepared by mechanical mixing.By using X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD),the chemical composition and crystal structure of Ag/pCF were examined,and scanning electron microscopy(SEM)was used to assess the surface morphology of the Ag/pCF.The results showed that a uniform and dense silver layer was formed on the surface of the CF,and the conductivity of the Ag/pCF could reach 7885 S/cm.It was noteworthy that the composite rubber filled with only 45 phr Ag/pCF had a high electromagnetic interference shielding effectiveness(100 dB)due to the low density and high aspect ratio of Ag/pCF.The composite rubber has excellent potential for application in the field of electro-magnetic interference shielding.
查看更多>>摘要：The mechanical behavior of polymer networks is intrinsically correlated with the local chain topology and chain connectivity.In this study,we delve into this relationship through the lens of coarse-grained molecular dynamics(CG-MD)simulations.Our aim is to illuminate the in-tricate interplay between local topology and stress distribution within polymer monomers,cross-linkers,and various components with distinct cross-link connections,thereby elucidating their collective impact on the mechanical properties of polymer networks.We mainly focus on how specific local structures contribute to the overall mechanical response of the network.In particular,we employ local stress analysis to unravel the mechanics of these structures.Our findings reveal the diverse responses of individual components,such as junctions,strands,cross-linkers be-tween junctions,and dangling chain ends,when subjected to stretching.Notably,we observe that these components exhibit varying degrees of deformation tolerance,underscoring the significance of their roles in determining the mechanical characteristics of the network.Our investiga-tions highlight junctions as primary contributors to stress accumulation,and particles with higher local stress showing a stronger correlation be-tween stress and Voronoi volume.Moreover,our results indicate that both strands and cross-linkers between junctions exhibit heightened stress levels as strand lengths decrease.This study enhances our understanding of the multifaceted factors governing the mechanical attributes of cross-linked polymer systems at the microstructural level.
查看更多>>摘要：The injection of a polymer chain into a small circular cavity under tangential self-propelled force is studied by using Langevin dynam-ics simulation.Results indicate that the injection dynamics of the active polymer shows strong correlation with the polymer conformation inside the cavity depending on the polymer rigidity(kb).The injection time τ varies nonmonotonously with increasingkb,and reaches its minimum at kb.When kb is small(kb＜＜kb"),the polymer is nearly random coil in the cavity,and spends a long time at the final stage of the injection process due to the large repulsion between monomers inside the cavity.When kb is moderate(kb～kb*),the part of polymer inside the cavity forms spiral configuration under the tangential active force,and the whole polymer moves synchronously with a constant velocity during the injection pro-cess,leading to a small injection time.When kb is large(kb＞＞kb*),the polymer is nearly straight at the initial stage of the injection process,and takes a long time to bend itself,leading to a large injection time.
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