Natural rubber nanocomposites filled with hybrid fillers of multi-walled carbon nanotubes(CNTs) and carbon black(CB) were prepared. CNTs were ultrasonically modified in mixture of hydrogen peroxide(H2O2) and distilled...Natural rubber nanocomposites filled with hybrid fillers of multi-walled carbon nanotubes(CNTs) and carbon black(CB) were prepared. CNTs were ultrasonically modified in mixture of hydrogen peroxide(H2O2) and distilled water(H2O). The functional groups on the surface of CNTs, changes in nanotube structure and morphology were characterized by Fourier transform infrared spectroscopy(FT-IR), Raman Spectroscopy, and transmission electron microscopy(TEM). It shows that hydroxyl(OH·) is successfully introduced. The surface defects of modified CNTs were obviously higher than those of original CNTs, and the degree of agglomeration was greatly reduced. Thermal conductivity of the composites was tested by protection heat flow meter method. Compared with unmodified CNTs/CB filling system, the thermal conductivity of hybrid composites is improved by an average of 5.8% with 1.5 phr(phr is parts per hundred rubber) of hydroxyl CNTs and 40 phr of CB filled. A three-dimensional heat conduction network composed of hydroxyl CNTs and CB, as observed by TEM, contributes to the good properties. Thermal conductivity of the hybrid composites increases as temperature rises. The mechanical properties of hybrid composites are also good with hydroxyl CNTs filled nanocomposites;the tensile strength, 100% and 300% tensile stress are improved by 10.1%, 22.4% and 26.2% respectively.展开更多
Non-noble-metal-based electrocatalysts with superior oxygen reduction reaction(ORR)activity to platinum(Pt)are highly desirable but their fabrications are challenging and thus impeding their applications in metal-air ...Non-noble-metal-based electrocatalysts with superior oxygen reduction reaction(ORR)activity to platinum(Pt)are highly desirable but their fabrications are challenging and thus impeding their applications in metal-air batteries and fuel cells.Here,we report a facile molten salt assisted two-step pyrolysis strategy to construct carbon nanosheets matrix with uniformly dispersed Fe_(3) N/Fe nanoparticles and abundant nitrogen-coordinated Fe single atom moieties(Fe@Fe_(SA)-N-C).Thermal exfoliation and etching effect of molten salt contribute to the formation of carbon nanosheets with high porosity,large surface area and abundant uniformly immobilized active sites.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)image,X-ray absorption fine spectroscopy,and X-ray photoelectron spectroscopy indicate the generation of Fe(mainly Fe_(3) N/Fe)and Fe_(SA)-N-C moieties,which account for the catalytic activity for ORR.Further study on modulating the crystal structure and composition of Fe_(3) N/Fe nanoparticles reveals that proper chemical environment of Fe in Fe_(3) N/Fe notably optimizes the ORR activity.Consequently,the presence of abundant Fe_(SA)-N-C moieties,and potential synergies of Fe_(3) N/Fe nanoparticles and carbon shells,markedly promote the reaction kinetics.The as-developed Fe@Fe_(SA)-N-C-900 electrocatalyst displays superior ORR performance with a half-wave potential(E_(1/2))of 0.83 V versus reversible hydrogen electrode(RHE)and a diffusion limited current density of 5.6 mA cm^(-2).In addition,a rechargeable Zn-air battery device assembled by the Fe@Fe_(SA)-N-C-900 possesses remarkably stable performance with a small voltage gap without obvious voltage loss after500 h of operation.The facile synthesis strategy for the high-performance composites represents another viable avenue to stable and low-cost electrocatalysts for ORR catalysis.展开更多
Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication ...Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.展开更多
It has increasingly become a research focus to build higher structure composed of C60. However, there has been very few reports on the influence of polymer addition on the self-assembling behavior of fullerene in orga...It has increasingly become a research focus to build higher structure composed of C60. However, there has been very few reports on the influence of polymer addition on the self-assembling behavior of fullerene in organic solvents. In this research, big needle-like C60 assemblings have been obtained in the form of PLLA/C60 composites. The largest C60 needles can be observed by naked eyes. The amount of C60 in the composite influences the length of C60 needles to some extent. DSC results indicate C60 accelerates the crystallization and lift the relative crystallinity of PLLA matrix. the results also imply the addition of semicrystalline PLLA influence the assembling behavior of C60. i.e., the crystallization of PLLA accelerated by C60 also act a driving force for the enriching and the linear assembling of C60 in PLLA matrix via Van der Waals force.展开更多
In this study,a novel cost-effective methodology was developed to enhance the gas barrier properties and permselectivity of unfilled natural rubber(NR)/polybutadiene rubber(BR)composites through the construction of a ...In this study,a novel cost-effective methodology was developed to enhance the gas barrier properties and permselectivity of unfilled natural rubber(NR)/polybutadiene rubber(BR)composites through the construction of a heterogeneous structure using pre-vulcanized powder rubber to replace traditional fillers.The matrix material is composed of a blend of NR and BR,which is widely used in tire manufacturing.By incorporating pre-vulcanized trans-1,4-poly(isoprene-co-butadiene)(TBIR)rubber powder(pVTPR)with different cross-linking densities and contents,significant improvements in the gas barrier properties and CO_(2)permselectivity of the NR/BR/pVTPR composites were observed.The results indicated that compared to NR/BR/TBIR composites prepared through direct blending of NR,BR,and TBIR,the NR/BR/pVTPR composites exhibited markedly superior gas barrier properties.Increasing the cross-linking density of pVTPR resulted in progressive enhancement of the gas barrier properties of the NR/BR/pVTPR composite.For example,the addition of 20 phr pVTPR with a cross-linking density of 346 mol/m^(3)resulted in a 79%improvement in the oxygen barrier property of NR/BR/pVTPR compared to NR/BR,achieving a value of 5.47×10^(-14)cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1).Similarly,the nitrogen barrier property improved by 76%compared to NR/BR,reaching 2.4×10^(-14)cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1),which is 28%higher than the conventional inner liner material brominated butyl rubber(BIIR,PN2=3.32×10^(-14)cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1)).Owing to its low cost,exceptional gas barrier properties,superior adhesion to various tire components,and co-vulcanization capabilities,the NR/BR/pVTPR composite has emerged as a promising alternative to butyl rubber in the inner liner of tires.Furthermore,by fine-tuning the cross-linking density of pVTPR,the high-gas-barrier NR/BR/pVTPR composites also demonstrated remarkable CO_(2)permselectivity,with a CO_(2)/N2 selectivity of 61.4 and a CO_(2)/O_(2)selectivity of 26.12.This innovation provides a novel strategy for CO_(2)capture and separation,with potential applications in future environmental and industrial processes.The multifunctional NR/BR/pVTPR composite,with its superior gas barrier properties and CO_(2)permselectivity,is expected to contribute to the development of safer,greener,and more cost-effective transportation solutions.展开更多
Poly(lactic acid)(PLA) as a bio-based polymer with biodegradability and biocompatibility has attracted much attention. To manipulate its properties for different applications, regulation of crystal structure and cryst...Poly(lactic acid)(PLA) as a bio-based polymer with biodegradability and biocompatibility has attracted much attention. To manipulate its properties for different applications, regulation of crystal structure and crystalline morphology becomes an attractive research topic. In this work, the structure evolution of layered samples containing an amorphous poly(D-lactide)(PDLA) layer and a crystalline poly(L-lactide)(PLLA)layer with highly oriented edge-on α lamellar crystals after annealing at 150 ℃ or/and after melt-recrystallization has been studied by AFM, FTIR,and TEM combined with electron diffraction. The results demonstrate that melt recrystallization of the as-prepared sample leads to the formation of abundant randomly oriented PLA stereo-complex(PLA SC) crystals. Annealing at 150 ℃ results in the formation of a small amount of oriented PLA SC crystals at the interface. These PLA SC crystals show great impact on the recrystallization behavior of sample after melting at 190 ℃ and then crystallizing at 90 ℃. First, they impede the mutual diffusion of the overlying PDLA and underlying PLLA, and thus reduce their stereocomplexation ability as manifested by the decreased amount of PLA SC crystals. Second, they act as substrate to initiate the epitaxial crystallization of the overlying PDLA and underlying PLLA, which ensures the production of a highly oriented structure of PDLA and PLLA after melt recrystallization again.展开更多
Realizing simultaneous adjustment of energy levels and work functions in two-dimensional/three-dimensional(2D/3D)perovskite solar cells(PSCs)is a challenge.Here,a pseudohalide 3,5-bis(trifluoromethyl)benzylammonium te...Realizing simultaneous adjustment of energy levels and work functions in two-dimensional/three-dimensional(2D/3D)perovskite solar cells(PSCs)is a challenge.Here,a pseudohalide 3,5-bis(trifluoromethyl)benzylammonium tetrafluoroborate(TFPMABF_(4))was used to react with unreacted Pb I2on the surface of 3D bulky perovskite to form a mixed halide of 2D perovskite denoted(TF-PMA)_(2)FA_(2)Pb_(3)I_(8)(BF_(4))_(2).This novel 2D/3D perovskite enables the simultaneous adjustment of energy levels and work functions on the surface of active layers.Due to the significantly enhanced quality of 2D/3D perovskite film,decreased surface defects and increased charge carrier lifetime,the 2D/3D PSCs exhibit an outstanding power conversion efficiency(PCE)of 25.15%and a high V_(OC)of 1.194 V.Importantly,2D/3D PSCs exhibit remarkable enhancements in environmental stability,unencapsulated devices retaining more than 90%of their initial PCE at 50%humidity for 2,280 h.展开更多
High-efficiency electroluminescent devices featuring simplified architecture have received considerable attention due to significant advantages in construction procedures and commercialized applications.However,there ...High-efficiency electroluminescent devices featuring simplified architecture have received considerable attention due to significant advantages in construction procedures and commercialized applications.However,there still remains a critical challenge with regard to the lack of organic semiconductors that simultaneously possess high luminescent efficiency and balanced carrier-transporting abilities.Herein,we design a thermally activated delayed fluorescence(TADF)emitter 4-(9,9-dimethyl-9,10-dihydroacridine)-4′-triphenylphosphineoxide-benzophenone(DMAC-BPTPO)by incorporating triphenylphosphine oxide into the donor–acceptor skeleton.The accessional electrontransporting moiety,rod-like dimer,and horizontally packing model synergistically enable DMAC-BP-TPO which possesses an excellent photoluminescence quantum yield of nearly 90%with a reverse intersystem crossing rate constant of 2.0×106 s−1,horizontal dipole ratio of 89%,and a balanced electron and hole mobilities with a small constrast ratio of 1.08.Eventually,simplified electroluminescent devices including organic lightemitting diodes(OLEDs)and organic light-emitting transistors(OLETs)incorporating DMAC-BP-TPO-based nondoped film are demonstrated due to their superior integrated optoelectronic properties along with preferable horizontal dipole orientation.A record-high external quantum efficiency value of 21.7%and 4.4%are finally achieved in the simplified nondoped OLED and OLET devices,which are among the highest values in the related research fields.This work provides a new avenue to develop a high-efficiency bipolar TADF emitter to advance the simplified electroluminescent devices.展开更多
Abstract Two series of trans-1,4-poly（butadiene-co-isoprene） copolymers （TBIR） were prepared using the catalyst system TiCl4/MgCl2-Al（i-Bu）3 at different reaction temperatures. All dyad and triads sequence distr...Abstract Two series of trans-1,4-poly（butadiene-co-isoprene） copolymers （TBIR） were prepared using the catalyst system TiCl4/MgCl2-Al（i-Bu）3 at different reaction temperatures. All dyad and triads sequence distributions, the number-average sequence length and the sequence concentration of the copolymers were calculated according to 13C-NMR spectra. The influences of temperature and initial molar ratio of butadiene to isoprene （Bd to Ip） on the distribution of the chain segments in the TBIR copolymers were discussed. The correlation of copolymer compositions and thermal properties were also evaluated, which facilitated the understanding of controlling the degree of crystallinity and the transition tempera^re by changing Bd content and temperature.展开更多
Polypropylene （PP）/polybutene-1 （PB） alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were ca...Polypropylene （PP）/polybutene-1 （PB） alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene （iPP） particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the iPP particles. Finally, iPP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly（butene- co-propylene） random copolymers and poly（butene-block-propylene） block copolymers. SEM measurements verified that the PB phases with size in the range of 300-400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.展开更多
To meet the increasing demand for safe, environmentally friendly and high-performance smart materials, self-healing rubbers are highly desired. Here, the self-healing performance of ethylene propylene diene monomer ru...To meet the increasing demand for safe, environmentally friendly and high-performance smart materials, self-healing rubbers are highly desired. Here, the self-healing performance of ethylene propylene diene monomer rubber (EPDM) is reported, which was designed by graft-polymerization of zinc dimethacrylate (ZDMA) onto rubber chains to form a reversible ionic cross-linked network. Single ionic cross-linked network and dual network, combining covalent and ionic cross-links, could be tuned by controlling vulcanization process to achieve tailorable mechanical and self-healing properties. It was found that ionic cross-linked EPDM showed a recovery of more than 95% of the original mechanical strength through a healing process of 1 h at 100 °C. The covalent cross-links could improve mechanical properties but block self-healing. Adding 50 wt% liquid rubber to “dry” EPDM could effectively enhance self-healing capability of the dual cross-linked network and the healed tensile strength could reach 0.9 MPa. A compromise between mechanical performance and healing capability could be potentially tailored by controlling vulcanization process and liquid rubber content.展开更多
A series of trans-1,4-butadiene/isoprene copolymers were prepared using the catalyst system TiCl4/MgCl2-Al（i- Bu）3 with bulk precipitation technology at different temperatures. Monomers reactivity ratios were calcul...A series of trans-1,4-butadiene/isoprene copolymers were prepared using the catalyst system TiCl4/MgCl2-Al（i- Bu）3 with bulk precipitation technology at different temperatures. Monomers reactivity ratios were calculated based on the Kelen-Tiid6s （K-T） method and the Mao-Huglin （M-H） method. The influence of temperature on copolymer composition and polymerization rate was discussed in detail. The increase of reaction temperature brought the decrease of butadiene reactivity ratio rBd and supplied an effective adjustment on copolymers＇ composition distribution.展开更多
The structural transformation of mesophase to crystalline phase of strain-induced poly(L-lactic acid) has been investigated by differential scanning calorimetry(DSC) and in situ temperature dependent polarized Fourier...The structural transformation of mesophase to crystalline phase of strain-induced poly(L-lactic acid) has been investigated by differential scanning calorimetry(DSC) and in situ temperature dependent polarized Fourier transform infrared(FTIR) spectroscopy. It is found that, as the drawing temperature increases, melting of strain-induced mesophase in the heating process can remarkably interfere the crystallization behavior subsequently. Coupling with in situ polarized FTIR, from 60 °C to 76 °C, the mesophase melts partially rather than completely melting, and changes immediately to three-dimensional ordered structure. Of particular note, through monitoring the subtle spectral change in the critical phase transformation temperature from 60 °C to 64 °C, it is clearly demonstrated that relaxation of oriented amorphous chains initially takes place prior to the melting of mesophase.展开更多
A sample containing different regions with poly(ε-caprolactone)(PCL), oriented polyethylene (PE), and oriented isotactic polypropylene (iPP) films in contact with glass slide has been prepared to be observed in the s...A sample containing different regions with poly(ε-caprolactone)(PCL), oriented polyethylene (PE), and oriented isotactic polypropylene (iPP) films in contact with glass slide has been prepared to be observed in the same view field in an optical microscope and the crystallization of PCL in different regions during cooling from 80 °C down to room temperature at a rate of 1 °C·min^-1 was studied. The results showed that the crystallization of PCL started first at the PE surface and then at the iPP surface, while its bulk crystallization occured much later. This indicates that though both PE and iPP are active in nucleating PCL, the nucleation ability of PE is stronger than that of iPP. This was due to a better lattice matching between PCL and PE than that between PCL and iPP. Moreover, since lattice matching existed between every (hk0) lattice planes of both PCL and PE but only between the (100)PCL and (010)iPP lattice planes, the uniaxial orientation feature of the used PE and iPP films resulted in the existence of much more active nucleation sites of PCL on PE than on iPP. This led to the fact that the nucleation density of PCL at PE surface was so high that the crystallization of PCL at PE surface took place in a way like the film developing process with PCL microcrystallites happened everywhere with crystallization proceeding simultaneously. On the other hand, even though iPP also enhanced the nucleation density of PCL evidently, the crystallization of PCL at iPP surface included still a nucleation and crystal growth processes similar to that of its bulk crystallization.展开更多
Since polymer-based light-emitting diodes(PLEDs)arewellsuited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high dem...Since polymer-based light-emitting diodes(PLEDs)arewellsuited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high demand.To respond to this demand,light-emitting TADF units have initially been modified with electron-transporting units to balance the carrier transport of regiorandom TADF polymers,and simultaneously,an intramolecular sensitizing strategy has also been employed by covalently incorporating TADF sensitizers with light-emitting TADF units and hosts in conjugated polymers to accelerate the spin-flip of triplet excitons.Superior photophysical properties have been achieved by a rational regulation of the proportions of each component,achieving a photoluminescence quantumyield of 90%,an extremely high rate of reverse intersystem crossing of 3×106 s−1,and a relatively low nonradiative decay rate of around 105 s−1.As a result,the solutionprocessed PLEDs can attain an external quantum efficiency(EQE)value of 25.4%with emission peaks of around 550 nm,representing record-high performance for PLEDs.The efficiency roll-off can also be significantly suppressed,maintaining an EQE value of 24.2%at 1000 cd/m2 with ideal efficiency roll-off of lower than 5%.Encouragingly,this work provides a valid strategy to tackle the imperative need for PLEDs with high EQE and low efficiency roll-off.展开更多
Isotactic poly（butene-1） （iPB） with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process ma...Isotactic poly（butene-1） （iPB） with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.展开更多
Diphenyl （4-hydroxyphenyl） hexadecyl phosphonium bromide （POH） -modified montmorillonite （POHMMT） was used to prepare a novel TiC14/MgC12/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were pr...Diphenyl （4-hydroxyphenyl） hexadecyl phosphonium bromide （POH） -modified montmorillonite （POHMMT） was used to prepare a novel TiC14/MgC12/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiC14/MgC12/POHMMT compound catalyst. The POH surfactants don＇t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na＋MMT nanocomposites were produced with the TiC14/MgC12/Na＋MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites.展开更多
A family of highly bulky bis(salicylaldiminate)Co(Ⅱ)complexes bearing cavity-like conformations are disclosed herein.Due to their unique bulky nature around the cobalt atoms that are reflected from space-filling mode...A family of highly bulky bis(salicylaldiminate)Co(Ⅱ)complexes bearing cavity-like conformations are disclosed herein.Due to their unique bulky nature around the cobalt atoms that are reflected from space-filling models and the buried volume percentages,obviously longer bond distances of Co―N and Co―O are revealed from those complexes.Moreover,because of these well-protected active species,the cobalt complexes are able to catalyze 1,3-butadiene polymerization in high yields at extreme low catalyst concentrations,revealing a ultra high catalytic efficiency.At a ratio of 50000,all the complexes can afford polybutadiene with yields higher than 90%.Furthermore,the highly steric bulkiness of the ligand can also significantly enhance the thermostability of the active species.At temperature of 80-120°C,the complexes are able to successfully maintain high activities,giving polymer yields up to 90%.展开更多
Macromolecule nanocrystal network and strong interfacial interaction are always beneficial to enhance the mechanical property of polymer-based nanocomposites.Poly(vinyl alcohol)(PVA),a typical biocompatible semicrysta...Macromolecule nanocrystal network and strong interfacial interaction are always beneficial to enhance the mechanical property of polymer-based nanocomposites.Poly(vinyl alcohol)(PVA),a typical biocompatible semicrystalline polymer,is an ideal candidate for preparing high performance polymer-based nanocomposites.However,the rich hydrogen bonds between PVA matrix and graphene oxide(GO)can disrupt the formation of PVA nanocrystal network.Thus,it remains a great challenge to achieve both strong and tough PVA-GO nanocomposites.Herein,by introducing a novel Janus-like amphiphilic graphene oxide(JGO),both hydrogen bonding and interfacial crystallization have been constructed between JGO sheets and PVA matrix.Benefiting from amphiphilic interfacial interaction and the enhanced crystal network,both PVA-JGO dried films and their swollen hydrogel films show superior mechanical properties than those of traditional PVA-GO nanocomposites.PVA-JGO dried films exhibit a 264%improvement of toughness at a JGO loading of 1 wt%.Meanwhile,the corresponding PVA-JGO swollen hydrogel films display simultaneous improvement of nearly 8 times increase of tensile strength and 20 times increase of toughness compared to traditional PVA-GO nanocomposite.This work indicates multiple interfacial interactions and macromolecule crystal networks can be concurrent in PVA nanocomposites by innovative modification of nanofillers,providing a new strategy to construct PVA nanocomposites with high strength and high toughness.The integration of outstanding mechanical and swelling resistance properties on PVA-JGO nanocomposite films render their promising applications,such as packaging and toughening hydrogel materials.展开更多
The effect of freezing layer on the crystallization kinetics of poly(ε-caprolactone)(PCL)thin and ultrathin films was investigated by monitor the growth process of it on oriented polyethylene(PE)and CaF_(2)with and w...The effect of freezing layer on the crystallization kinetics of poly(ε-caprolactone)(PCL)thin and ultrathin films was investigated by monitor the growth process of it on oriented polyethylene(PE)and CaF_(2)with and without freezing layer,respectively.It was found that the PCL films with similar thicknesses crystallize much faster on oriented PE than on CaF_(2)substrate.For example,the crystallization rate constant of a 102 nm thick PCL film decreases tremendously by 3 orders of magnitude from 1.1×10^(-1) on PE substrate at 50℃to 7×10^(-4)on CaF_(2)surface at 40℃.Moreover,the crystallization of PCL accelerates on CaF_(2)surface while slows down at PE surface with increasing film thickness.The ultrathin films of PCL with thickness less than 14 nm exhibits the fastest crystallization rate on oriented PE with a rate constant of about 3.5×10^(-1),which is 3 times higher than that of a ca.50 nm thick film.This illustrates the great influence of freezing layer on the crystallization process of PCL.The freezing layer thickness of PCL on PE is estimated to be in the range of 14-17 nm.Taking the radius of gyration(R_(g)~15.6 nm)of the used PCL material into account,the obtained results may imply the existence of a correlation between the R_(g)of PCL and its freezing layer thickness at PE substrate.展开更多
基金Supported by the National Natural Science Foundation of China(51606107,51576102)the Collaborative Innovation Project of Green Tire and Rubber(0200501436)
文摘Natural rubber nanocomposites filled with hybrid fillers of multi-walled carbon nanotubes(CNTs) and carbon black(CB) were prepared. CNTs were ultrasonically modified in mixture of hydrogen peroxide(H2O2) and distilled water(H2O). The functional groups on the surface of CNTs, changes in nanotube structure and morphology were characterized by Fourier transform infrared spectroscopy(FT-IR), Raman Spectroscopy, and transmission electron microscopy(TEM). It shows that hydroxyl(OH·) is successfully introduced. The surface defects of modified CNTs were obviously higher than those of original CNTs, and the degree of agglomeration was greatly reduced. Thermal conductivity of the composites was tested by protection heat flow meter method. Compared with unmodified CNTs/CB filling system, the thermal conductivity of hybrid composites is improved by an average of 5.8% with 1.5 phr(phr is parts per hundred rubber) of hydroxyl CNTs and 40 phr of CB filled. A three-dimensional heat conduction network composed of hydroxyl CNTs and CB, as observed by TEM, contributes to the good properties. Thermal conductivity of the hybrid composites increases as temperature rises. The mechanical properties of hybrid composites are also good with hydroxyl CNTs filled nanocomposites;the tensile strength, 100% and 300% tensile stress are improved by 10.1%, 22.4% and 26.2% respectively.
基金supported financially by the National Natural Science Foundation of China,China(Grant No.51702180,51772162)the Taishan Scholar Advantage and Characteristic Discipline Team of Eco Chemical Process and Technologythe Scientific and Technical Development Project of Qingdao,China(Grant No.18-2-2-52-jch)。
文摘Non-noble-metal-based electrocatalysts with superior oxygen reduction reaction(ORR)activity to platinum(Pt)are highly desirable but their fabrications are challenging and thus impeding their applications in metal-air batteries and fuel cells.Here,we report a facile molten salt assisted two-step pyrolysis strategy to construct carbon nanosheets matrix with uniformly dispersed Fe_(3) N/Fe nanoparticles and abundant nitrogen-coordinated Fe single atom moieties(Fe@Fe_(SA)-N-C).Thermal exfoliation and etching effect of molten salt contribute to the formation of carbon nanosheets with high porosity,large surface area and abundant uniformly immobilized active sites.Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)image,X-ray absorption fine spectroscopy,and X-ray photoelectron spectroscopy indicate the generation of Fe(mainly Fe_(3) N/Fe)and Fe_(SA)-N-C moieties,which account for the catalytic activity for ORR.Further study on modulating the crystal structure and composition of Fe_(3) N/Fe nanoparticles reveals that proper chemical environment of Fe in Fe_(3) N/Fe notably optimizes the ORR activity.Consequently,the presence of abundant Fe_(SA)-N-C moieties,and potential synergies of Fe_(3) N/Fe nanoparticles and carbon shells,markedly promote the reaction kinetics.The as-developed Fe@Fe_(SA)-N-C-900 electrocatalyst displays superior ORR performance with a half-wave potential(E_(1/2))of 0.83 V versus reversible hydrogen electrode(RHE)and a diffusion limited current density of 5.6 mA cm^(-2).In addition,a rechargeable Zn-air battery device assembled by the Fe@Fe_(SA)-N-C-900 possesses remarkably stable performance with a small voltage gap without obvious voltage loss after500 h of operation.The facile synthesis strategy for the high-performance composites represents another viable avenue to stable and low-cost electrocatalysts for ORR catalysis.
基金supported financially by the National Natural Science Foundation of China,China(Grant No.51702180,51572136,91963113,21703116,51372127,51873096)The Scientific and Technical Development Project of Qingdao,China(Grant No.18-2-2-52-jch)+1 种基金The Taishan Scholar Advantage and Characteristic Discipline Team of Eco Chemical Process and TechnologyThe Natural Science Foundation of Hebei Province(B2019204009)。
文摘Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.
文摘It has increasingly become a research focus to build higher structure composed of C60. However, there has been very few reports on the influence of polymer addition on the self-assembling behavior of fullerene in organic solvents. In this research, big needle-like C60 assemblings have been obtained in the form of PLLA/C60 composites. The largest C60 needles can be observed by naked eyes. The amount of C60 in the composite influences the length of C60 needles to some extent. DSC results indicate C60 accelerates the crystallization and lift the relative crystallinity of PLLA matrix. the results also imply the addition of semicrystalline PLLA influence the assembling behavior of C60. i.e., the crystallization of PLLA accelerated by C60 also act a driving force for the enriching and the linear assembling of C60 in PLLA matrix via Van der Waals force.
基金supported by the National Key Research and Development Program of China (No. 2022YFB3704700(2022YFB3704702))the National Natural Science Foundation of China (No. 52473096)+1 种基金Major Scientific and Technological Innovation Project of Shandong Province (No. 2021CXGC010901)Taishan Scholar Program
文摘In this study,a novel cost-effective methodology was developed to enhance the gas barrier properties and permselectivity of unfilled natural rubber(NR)/polybutadiene rubber(BR)composites through the construction of a heterogeneous structure using pre-vulcanized powder rubber to replace traditional fillers.The matrix material is composed of a blend of NR and BR,which is widely used in tire manufacturing.By incorporating pre-vulcanized trans-1,4-poly(isoprene-co-butadiene)(TBIR)rubber powder(pVTPR)with different cross-linking densities and contents,significant improvements in the gas barrier properties and CO_(2)permselectivity of the NR/BR/pVTPR composites were observed.The results indicated that compared to NR/BR/TBIR composites prepared through direct blending of NR,BR,and TBIR,the NR/BR/pVTPR composites exhibited markedly superior gas barrier properties.Increasing the cross-linking density of pVTPR resulted in progressive enhancement of the gas barrier properties of the NR/BR/pVTPR composite.For example,the addition of 20 phr pVTPR with a cross-linking density of 346 mol/m^(3)resulted in a 79%improvement in the oxygen barrier property of NR/BR/pVTPR compared to NR/BR,achieving a value of 5.47×10^(-14)cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1).Similarly,the nitrogen barrier property improved by 76%compared to NR/BR,reaching 2.4×10^(-14)cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1),which is 28%higher than the conventional inner liner material brominated butyl rubber(BIIR,PN2=3.32×10^(-14)cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1)).Owing to its low cost,exceptional gas barrier properties,superior adhesion to various tire components,and co-vulcanization capabilities,the NR/BR/pVTPR composite has emerged as a promising alternative to butyl rubber in the inner liner of tires.Furthermore,by fine-tuning the cross-linking density of pVTPR,the high-gas-barrier NR/BR/pVTPR composites also demonstrated remarkable CO_(2)permselectivity,with a CO_(2)/N2 selectivity of 61.4 and a CO_(2)/O_(2)selectivity of 26.12.This innovation provides a novel strategy for CO_(2)capture and separation,with potential applications in future environmental and industrial processes.The multifunctional NR/BR/pVTPR composite,with its superior gas barrier properties and CO_(2)permselectivity,is expected to contribute to the development of safer,greener,and more cost-effective transportation solutions.
基金financially supported by the National Natural Science Foundation of China (Nos. 52027804 and 22022501)Postgraduate Independent Innovation Project (No. B2022KY004,Qingdao University of Science and Technology)。
文摘Poly(lactic acid)(PLA) as a bio-based polymer with biodegradability and biocompatibility has attracted much attention. To manipulate its properties for different applications, regulation of crystal structure and crystalline morphology becomes an attractive research topic. In this work, the structure evolution of layered samples containing an amorphous poly(D-lactide)(PDLA) layer and a crystalline poly(L-lactide)(PLLA)layer with highly oriented edge-on α lamellar crystals after annealing at 150 ℃ or/and after melt-recrystallization has been studied by AFM, FTIR,and TEM combined with electron diffraction. The results demonstrate that melt recrystallization of the as-prepared sample leads to the formation of abundant randomly oriented PLA stereo-complex(PLA SC) crystals. Annealing at 150 ℃ results in the formation of a small amount of oriented PLA SC crystals at the interface. These PLA SC crystals show great impact on the recrystallization behavior of sample after melting at 190 ℃ and then crystallizing at 90 ℃. First, they impede the mutual diffusion of the overlying PDLA and underlying PLLA, and thus reduce their stereocomplexation ability as manifested by the decreased amount of PLA SC crystals. Second, they act as substrate to initiate the epitaxial crystallization of the overlying PDLA and underlying PLLA, which ensures the production of a highly oriented structure of PDLA and PLLA after melt recrystallization again.
基金supported by the National Natural Science Foundation of China(21875122)。
文摘Realizing simultaneous adjustment of energy levels and work functions in two-dimensional/three-dimensional(2D/3D)perovskite solar cells(PSCs)is a challenge.Here,a pseudohalide 3,5-bis(trifluoromethyl)benzylammonium tetrafluoroborate(TFPMABF_(4))was used to react with unreacted Pb I2on the surface of 3D bulky perovskite to form a mixed halide of 2D perovskite denoted(TF-PMA)_(2)FA_(2)Pb_(3)I_(8)(BF_(4))_(2).This novel 2D/3D perovskite enables the simultaneous adjustment of energy levels and work functions on the surface of active layers.Due to the significantly enhanced quality of 2D/3D perovskite film,decreased surface defects and increased charge carrier lifetime,the 2D/3D PSCs exhibit an outstanding power conversion efficiency(PCE)of 25.15%and a high V_(OC)of 1.194 V.Importantly,2D/3D PSCs exhibit remarkable enhancements in environmental stability,unencapsulated devices retaining more than 90%of their initial PCE at 50%humidity for 2,280 h.
基金financial support from the National Natural Science Foundation of China(grant nos.52103220,52273164,and 52233010)the Shandong Provincial Natural Science Foundation(grant nos.ZR2022ZD37 and ZR2023QE078)+4 种基金the Ministry of Science and Technology of China(grant nos.2022YFB3603800 and 2018YFA0703200)the Fundamental Research Funds for the Central Universities(grant no.QNTD20)the Beijing National Laboratory for Molecular Sciences(grant no.BNLMS-CXXM-202012)the Natural Science Foundation of Qingdao(grant no.23-2-1-75-zyyd-jch)the Shandong Provincial Regular Undergraduate University Teacher Visiting and Training Fund.
文摘High-efficiency electroluminescent devices featuring simplified architecture have received considerable attention due to significant advantages in construction procedures and commercialized applications.However,there still remains a critical challenge with regard to the lack of organic semiconductors that simultaneously possess high luminescent efficiency and balanced carrier-transporting abilities.Herein,we design a thermally activated delayed fluorescence(TADF)emitter 4-(9,9-dimethyl-9,10-dihydroacridine)-4′-triphenylphosphineoxide-benzophenone(DMAC-BPTPO)by incorporating triphenylphosphine oxide into the donor–acceptor skeleton.The accessional electrontransporting moiety,rod-like dimer,and horizontally packing model synergistically enable DMAC-BP-TPO which possesses an excellent photoluminescence quantum yield of nearly 90%with a reverse intersystem crossing rate constant of 2.0×106 s−1,horizontal dipole ratio of 89%,and a balanced electron and hole mobilities with a small constrast ratio of 1.08.Eventually,simplified electroluminescent devices including organic lightemitting diodes(OLEDs)and organic light-emitting transistors(OLETs)incorporating DMAC-BP-TPO-based nondoped film are demonstrated due to their superior integrated optoelectronic properties along with preferable horizontal dipole orientation.A record-high external quantum efficiency value of 21.7%and 4.4%are finally achieved in the simplified nondoped OLED and OLET devices,which are among the highest values in the related research fields.This work provides a new avenue to develop a high-efficiency bipolar TADF emitter to advance the simplified electroluminescent devices.
基金financially supported by the National Basic Research Program of China(No.2015CB654700(2015CB654706))Shandong Province Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the National Natural Science Foundation of China(No.51473083)
文摘Abstract Two series of trans-1,4-poly（butadiene-co-isoprene） copolymers （TBIR） were prepared using the catalyst system TiCl4/MgCl2-Al（i-Bu）3 at different reaction temperatures. All dyad and triads sequence distributions, the number-average sequence length and the sequence concentration of the copolymers were calculated according to 13C-NMR spectra. The influences of temperature and initial molar ratio of butadiene to isoprene （Bd to Ip） on the distribution of the chain segments in the TBIR copolymers were discussed. The correlation of copolymer compositions and thermal properties were also evaluated, which facilitated the understanding of controlling the degree of crystallinity and the transition tempera^re by changing Bd content and temperature.
基金financially supported by the National Natural Science Foundation of China(Nos.21174074,20774098)National Scientific Supporting Program from Ministry of Science and Technology of China(No.2011BAE26B05)
文摘Polypropylene （PP）/polybutene-1 （PB） alloys within reactor were prepared by MgCl2-supported Ziegler-Natta catalyst with sequential two-stage polymerization technology. First, propylene homo-polymerizations were carried out to form isotactic polypropylene （iPP） particles containing active catalyst. Then, butene-1 was subsequently polymerized to form polybutene-1 phase inside the iPP particles. Finally, iPP/PB alloys with spherical shape and adjustable PB content were synthesized. The catalytic activity and catalytic stereospecificity of the Z-N catalyst in the two-stage polymerization process are discussed. The composition and physical properties of the PP alloys were characterized by FT-IR, 13C-NMR, SEM, DSC and XRD. It was found that the in-reactor PP alloys are mainly composed of PP and PB with a little amount of poly（butene- co-propylene） random copolymers and poly（butene-block-propylene） block copolymers. SEM measurements verified that the PB phases with size in the range of 300-400 nm dispersed in the PP matrix uniformly. The incorporation of PB upon the PP matrix affects the properties of final products greatly.
基金financially supported by the National Basic Research Program of China (Nos. 2015CB654700 and 2015CB654706)the National Natural Science Foundation of China (No. 51403115)the Key Laboratory of Rubber-Plastics, Ministry of Education/ Shandong Provincial Key Laboratory of Rubber-plastics of Qingdao University of Science & Technology (KF2017008)
文摘To meet the increasing demand for safe, environmentally friendly and high-performance smart materials, self-healing rubbers are highly desired. Here, the self-healing performance of ethylene propylene diene monomer rubber (EPDM) is reported, which was designed by graft-polymerization of zinc dimethacrylate (ZDMA) onto rubber chains to form a reversible ionic cross-linked network. Single ionic cross-linked network and dual network, combining covalent and ionic cross-links, could be tuned by controlling vulcanization process to achieve tailorable mechanical and self-healing properties. It was found that ionic cross-linked EPDM showed a recovery of more than 95% of the original mechanical strength through a healing process of 1 h at 100 °C. The covalent cross-links could improve mechanical properties but block self-healing. Adding 50 wt% liquid rubber to “dry” EPDM could effectively enhance self-healing capability of the dual cross-linked network and the healed tensile strength could reach 0.9 MPa. A compromise between mechanical performance and healing capability could be potentially tailored by controlling vulcanization process and liquid rubber content.
基金financially supported by the National Key Technology R&D Program of China(No.2011BAE26B05)the Shandong Province Natural Science Fund for Distinguished Young Scholars(No.JQ201213)+2 种基金National Natural Science Foundation of China(No.21174074)Shandong Province Science and Technology Development Plan(No.2012GGA05042)the Major Projects of Independent Innovation Achievements Transformation in Shandong Province(No.2013ZHZX1A0207)
文摘A series of trans-1,4-butadiene/isoprene copolymers were prepared using the catalyst system TiCl4/MgCl2-Al（i- Bu）3 with bulk precipitation technology at different temperatures. Monomers reactivity ratios were calculated based on the Kelen-Tiid6s （K-T） method and the Mao-Huglin （M-H） method. The influence of temperature on copolymer composition and polymerization rate was discussed in detail. The increase of reaction temperature brought the decrease of butadiene reactivity ratio rBd and supplied an effective adjustment on copolymers＇ composition distribution.
基金financial supports from the National Natural Science Foundation of China(Nos.21774068 and 21704053)Natural Science Foundation of Shandong Province(No.ZR2017BB069)
文摘The structural transformation of mesophase to crystalline phase of strain-induced poly(L-lactic acid) has been investigated by differential scanning calorimetry(DSC) and in situ temperature dependent polarized Fourier transform infrared(FTIR) spectroscopy. It is found that, as the drawing temperature increases, melting of strain-induced mesophase in the heating process can remarkably interfere the crystallization behavior subsequently. Coupling with in situ polarized FTIR, from 60 °C to 76 °C, the mesophase melts partially rather than completely melting, and changes immediately to three-dimensional ordered structure. Of particular note, through monitoring the subtle spectral change in the critical phase transformation temperature from 60 °C to 64 °C, it is clearly demonstrated that relaxation of oriented amorphous chains initially takes place prior to the melting of mesophase.
文摘A sample containing different regions with poly(ε-caprolactone)(PCL), oriented polyethylene (PE), and oriented isotactic polypropylene (iPP) films in contact with glass slide has been prepared to be observed in the same view field in an optical microscope and the crystallization of PCL in different regions during cooling from 80 °C down to room temperature at a rate of 1 °C·min^-1 was studied. The results showed that the crystallization of PCL started first at the PE surface and then at the iPP surface, while its bulk crystallization occured much later. This indicates that though both PE and iPP are active in nucleating PCL, the nucleation ability of PE is stronger than that of iPP. This was due to a better lattice matching between PCL and PE than that between PCL and iPP. Moreover, since lattice matching existed between every (hk0) lattice planes of both PCL and PE but only between the (100)PCL and (010)iPP lattice planes, the uniaxial orientation feature of the used PE and iPP films resulted in the existence of much more active nucleation sites of PCL on PE than on iPP. This led to the fact that the nucleation density of PCL at PE surface was so high that the crystallization of PCL at PE surface took place in a way like the film developing process with PCL microcrystallites happened everywhere with crystallization proceeding simultaneously. On the other hand, even though iPP also enhanced the nucleation density of PCL evidently, the crystallization of PCL at iPP surface included still a nucleation and crystal growth processes similar to that of its bulk crystallization.
基金the National Natural Science Foundation of China(nos.51922021 and 52103220)the Shandong Provincial Natural Science Foundation(no.ZR2019ZD50).
文摘Since polymer-based light-emitting diodes(PLEDs)arewellsuited building blocks for large-area and low-cost flexible display equipment,state-of-the-art thermally activated delayed fluorescence(TADF)PLEDs are in high demand.To respond to this demand,light-emitting TADF units have initially been modified with electron-transporting units to balance the carrier transport of regiorandom TADF polymers,and simultaneously,an intramolecular sensitizing strategy has also been employed by covalently incorporating TADF sensitizers with light-emitting TADF units and hosts in conjugated polymers to accelerate the spin-flip of triplet excitons.Superior photophysical properties have been achieved by a rational regulation of the proportions of each component,achieving a photoluminescence quantumyield of 90%,an extremely high rate of reverse intersystem crossing of 3×106 s−1,and a relatively low nonradiative decay rate of around 105 s−1.As a result,the solutionprocessed PLEDs can attain an external quantum efficiency(EQE)value of 25.4%with emission peaks of around 550 nm,representing record-high performance for PLEDs.The efficiency roll-off can also be significantly suppressed,maintaining an EQE value of 24.2%at 1000 cd/m2 with ideal efficiency roll-off of lower than 5%.Encouragingly,this work provides a valid strategy to tackle the imperative need for PLEDs with high EQE and low efficiency roll-off.
基金financially supported by the National Key Technology R&D Program of China(No.2011BAE26B05)
文摘Isotactic poly（butene-1） （iPB） with spherical morphology was synthesized successfully with bulk precipitation polymerization without post-treatment of the products. The bulk precipitation polymerization process made it possible for iPB to be used as general plastic due to the acceptable decreased cost compared with the solution polymerization process. The influence of catalyst residues on the aging and thermal stability of iPB synthesized by bulk precipitation polymerization method was investigated by gel permeation chromatography, mechanical performance testing, thermogravimetric analysis and infrared spectroscopic analysis. Commercial iPB and the lab-made iPB with varied catalyst residue contents were studied. The results demonstrated that the catalyst residues played an important role in the aging process of the iPB. A possible mechanism of aging promotion by catalyst residues was proposed.
基金financially supported by the National Natural Science Foundation of China(Nos.20774098,21174074 and 51003050)the National Key Technology R&D Program of China(No.2011BAE26B05)Shandong Province Natural Science Fund for Distinguished Young Scholars(No.JQ201213)
文摘Diphenyl （4-hydroxyphenyl） hexadecyl phosphonium bromide （POH） -modified montmorillonite （POHMMT） was used to prepare a novel TiC14/MgC12/POHMMT compound catalyst and exfoliated iPP/POHMMT nanocomposites were prepared by the in situ intercalative polymerization of propylene with the TiC14/MgC12/POHMMT compound catalyst. The POH surfactants don＇t change the catalytic characteristic of the Z-N catalyst and the obtained PP presents high isotacticity, normal molecular weight and molecular weight distribution. The WAXD, SAXS and TEM results demonstrate the highly exfoliated iPP/POHMMT nanocomposites were produced by the in situ polymerization with this novel catalyst, while the intercalated iPP/Na＋MMT nanocomposites were produced with the TiC14/MgC12/Na＋MMT compound catalyst. Through this approach, in situ propylene polymerization can actually take place between the silicate layers and lead not only to PP with high isotacticity and molecular weight, but also to highly exfoliated PP nanocomposites.
基金financially supported by the National Natural Science Foundation of China(Nos.U1862206 and 21801236)。
文摘A family of highly bulky bis(salicylaldiminate)Co(Ⅱ)complexes bearing cavity-like conformations are disclosed herein.Due to their unique bulky nature around the cobalt atoms that are reflected from space-filling models and the buried volume percentages,obviously longer bond distances of Co―N and Co―O are revealed from those complexes.Moreover,because of these well-protected active species,the cobalt complexes are able to catalyze 1,3-butadiene polymerization in high yields at extreme low catalyst concentrations,revealing a ultra high catalytic efficiency.At a ratio of 50000,all the complexes can afford polybutadiene with yields higher than 90%.Furthermore,the highly steric bulkiness of the ligand can also significantly enhance the thermostability of the active species.At temperature of 80-120°C,the complexes are able to successfully maintain high activities,giving polymer yields up to 90%.
基金the National Natural Science Foundation of China(Nos.51773103 and 51603112)Taishan Mountain Scholar Foundation(Nos.TS20081120 and tshw20110510)State Key Laboratory of Bio-Fibers and EcoTextiles(Qingdao University)(No.K2019-09).
文摘Macromolecule nanocrystal network and strong interfacial interaction are always beneficial to enhance the mechanical property of polymer-based nanocomposites.Poly(vinyl alcohol)(PVA),a typical biocompatible semicrystalline polymer,is an ideal candidate for preparing high performance polymer-based nanocomposites.However,the rich hydrogen bonds between PVA matrix and graphene oxide(GO)can disrupt the formation of PVA nanocrystal network.Thus,it remains a great challenge to achieve both strong and tough PVA-GO nanocomposites.Herein,by introducing a novel Janus-like amphiphilic graphene oxide(JGO),both hydrogen bonding and interfacial crystallization have been constructed between JGO sheets and PVA matrix.Benefiting from amphiphilic interfacial interaction and the enhanced crystal network,both PVA-JGO dried films and their swollen hydrogel films show superior mechanical properties than those of traditional PVA-GO nanocomposites.PVA-JGO dried films exhibit a 264%improvement of toughness at a JGO loading of 1 wt%.Meanwhile,the corresponding PVA-JGO swollen hydrogel films display simultaneous improvement of nearly 8 times increase of tensile strength and 20 times increase of toughness compared to traditional PVA-GO nanocomposite.This work indicates multiple interfacial interactions and macromolecule crystal networks can be concurrent in PVA nanocomposites by innovative modification of nanofillers,providing a new strategy to construct PVA nanocomposites with high strength and high toughness.The integration of outstanding mechanical and swelling resistance properties on PVA-JGO nanocomposite films render their promising applications,such as packaging and toughening hydrogel materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52103017 and 52027804)。
文摘The effect of freezing layer on the crystallization kinetics of poly(ε-caprolactone)(PCL)thin and ultrathin films was investigated by monitor the growth process of it on oriented polyethylene(PE)and CaF_(2)with and without freezing layer,respectively.It was found that the PCL films with similar thicknesses crystallize much faster on oriented PE than on CaF_(2)substrate.For example,the crystallization rate constant of a 102 nm thick PCL film decreases tremendously by 3 orders of magnitude from 1.1×10^(-1) on PE substrate at 50℃to 7×10^(-4)on CaF_(2)surface at 40℃.Moreover,the crystallization of PCL accelerates on CaF_(2)surface while slows down at PE surface with increasing film thickness.The ultrathin films of PCL with thickness less than 14 nm exhibits the fastest crystallization rate on oriented PE with a rate constant of about 3.5×10^(-1),which is 3 times higher than that of a ca.50 nm thick film.This illustrates the great influence of freezing layer on the crystallization process of PCL.The freezing layer thickness of PCL on PE is estimated to be in the range of 14-17 nm.Taking the radius of gyration(R_(g)~15.6 nm)of the used PCL material into account,the obtained results may imply the existence of a correlation between the R_(g)of PCL and its freezing layer thickness at PE substrate.
