Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions,but the low selectivity of styrene is difficult to be improved with by-products of ...Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions,but the low selectivity of styrene is difficult to be improved with by-products of ethylbenzene and xylene.In this study,a new way is introduced to improve the catalytic performance by means of assisting basic compounds as co-catalysts during the toluene side-chain alkylation with methanol to styrene.As a result,high activity of side-chain alkylation appears over the basic Cs-modified zeolite catalysts prepared by ion exchange and impregnation methods.This high performance should be mainly attributed to two co-catalysis actions:(1)the promotion of basic compounds for methanol dehydrogenation to formaldehyde as the intermediate for side-chain alkylation;(2)the suppression of the styrene transfer hydrogenation on basic Cs-modified zeolites to avoid the formation of ethylbenzene.Especially for Cs_(2)O/CsX-ex catalyst,the addition of 2%mol/mol 2-picoline in reaction mixture could achieve both 12.3%toluene conversion and 84.1%styrene selectivity.Whereas the higher concentration of 2-picoline(>6%mol/mol)caused an inhibition to the catalytic activity because the excessive basic compound poisoned the combined acid-base pathway required for the side-chain alkylation process.In addition,two possible side-chain alkylation reaction routes on Cs-modified zeolite under the different 2-picoline absorption were described.展开更多
A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily 'tunab1e' by simple mechanical perturbation. Thepolymerization...A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily 'tunab1e' by simple mechanical perturbation. Thepolymerization of 10- [ 4 - (4' -methoxyphenoxycarbonyl )phenoxycarbonyl] - 1 -decyne (4 ) in itiated by theWCl_6-Ph_4Sn/dioxane complex yields polymer 5 with a M_w of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.展开更多
Side-chain modification is a proven effective approach for morphology manipulation in organic solar cells(OSCs).However,in-depth analysis and investigation involving side-chain modification towards morphology improvem...Side-chain modification is a proven effective approach for morphology manipulation in organic solar cells(OSCs).However,in-depth analysis and investigation involving side-chain modification towards morphology improvement,including molecular microstructure,orientating packing and aggregation are urgent for all-small-molecule(ASM)systems.Herein,employing a fluorine-modified two-dimension benzodithiophene(BDT)as central unit,we contrastively synthesized two small-molecule donors,namely BDT-F-SR and BDT-F-R,each welding alkylthio side-chains on thienyl of central BDT unit and the other grafted non-sulfuric alkyl side-chains.As predicted,the synergetic side-chain modification of fluorination and alkyl changeover triggers diverse molecular dipole moments and orientations,resulting in different molecular energy levels,thermal stabilities,molecular planarity and order.Eventually,together with the preeminent small-molecule acceptor Y6,BDT-F-R-based ASM OSCs obtain enhanced power conversion efficiency(PCE)of 13.88%compared to BDT-F-SR-based devices(PCE of 12.75%)with more suitable phase-separation and balanced carrier mobilities.The contrast results reveal that alkyl sidechains seem to be a more satisfactory partner for fluorine-modified 2D BDT-based small-molecule donors compared to alkylthio pendants,and highlight the significance of subtle side-chain modification for molecular structural order fun-tuning and morphology control,laying the foundation for efficient ASM OSCs.展开更多
The morphological changes of a side-chain liquid-crystalline polymethacrylate during isotropization and liquid-crystallization transitions were studied by means of polarizing microscopy. These transitions were found t...The morphological changes of a side-chain liquid-crystalline polymethacrylate during isotropization and liquid-crystallization transitions were studied by means of polarizing microscopy. These transitions were found to be composed of the initiation of a new phase at local places of the old phase matrix and the growth of the new phase: domains. The kinetics of the liquid-crystallization of the polymer from an isotropic melt to a smectic mesophase was also investigated. The isothermal process of the transition can be described by the Avrami equation. The values of the Avrami exponent were found to be around 2.6. which is lower than the value usually obtained for crystallization transition of polymers, but larger than that reported for liquid-crystallization transition of main-chain polymers. These results may indicate the difference in growth geometry of new phase during transition between crystallization and liquid-crystallization in general and between liquid-crystallization of main-chain and side-chain polymers. It was found that the liquid-crystallization of the used side-chain polymethacrylate may occur at small undercoolings with high transformation rate similar to that of main-chain polymers and small-molecule liquid crystals, while the crystallization of polymers can only proceed at large undercoolings. These phenomena can be explained by the idea that the surface free energy of nucleus during liquid-crystallization transition is less than that for crystallization, and evidence was obtained from analysis of the temperature dependence of the transformation rate.展开更多
Photoluminescence properties and exciton decay dynamics in a porphyrin side-chain polymer, poly[porphyrin acrylate- acrylonitrile (abbreviated p[(por)A-AN]), have been investigated by femtosecond time-resolved pho...Photoluminescence properties and exciton decay dynamics in a porphyrin side-chain polymer, poly[porphyrin acrylate- acrylonitrile (abbreviated p[(por)A-AN]), have been investigated by femtosecond time-resolved photoluminescence spectroscopy. All the luminescences of p[(por)A-AN] films are due to the emissive decay of the photoexcited singlet excitons in the porphyrins. The luminescence efficiencies and lifetimes are increased for samples from pure films to dilute blend films. However, they are increased as the intrachain concentration of the porphyrin sidechain groups is decreased. The intrachain rotation motions of porphyrin sidechain groups result in the initial ultrafast luminescence decays, which are much faster than those due to the interchain interactions. All the samples show no significant red-shift and broadening of the transient luminescence spectra. The interchain and intrachain nonradiative exciton relaxation processes may play an important role in the luminescence dynamics in the p[(por)A-AN] films. The possible origin of different intrachain and interchain dynamic behaviours in p[(por)A-AN] films is discussed.展开更多
The morphological features of a side-chain liquid crystalline polymer during the mesophase transitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogens of three benzene rin...The morphological features of a side-chain liquid crystalline polymer during the mesophase transitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogens of three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture was observed in the transition temperature range. Similar to main-chain liquid crystalline polymers the transition process of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local places of the old phase matrix and a growth process of the new phase domains.展开更多
This is a part of our systematic research work on polyimides with mesogenic unit side chain. In this study, a new 4'-phenylpbenyl 4-(3",5"-diaminobenzoyloxy)benzoate and polyimide were synthesized, and characteri...This is a part of our systematic research work on polyimides with mesogenic unit side chain. In this study, a new 4'-phenylpbenyl 4-(3",5"-diaminobenzoyloxy)benzoate and polyimide were synthesized, and characterized by FTIR, ^1H-NMR, inherent viscosity, mechanical properties, and solubility measurements. The diamine composed with mesogenic unit aryl ester groups and bipbenyl group with longer L/D ratio, was synthesized by two key steps. Firstly, the hydroxy group of 4-hydroxybenzoic acid was protected by acetoxy group for avoiding self- polymerization of 4-hydroxybenzoic acid, and then selectively hydrolyzed after esterification of carboxyl. Secondly, a selective catalysis hydrogenation was adopted to prevent the aryl ester from deoxidation. Based on this diamine, a novel polyimide was prepared by polycondensation of 4'-phenylphenyl 4-(3", 5"-diaminobenzoyloxy)benzoate and 4-aminophenyl ether(ODA) with 4, 4'-oxydiphthalic anhydride(ODPA) in N-methyl-2-pyrrolidone (NMP). The resulting polyimide with longer side chain showed better solubility and more regular structure. Its inherent viscosity is lower than that without side chains, but its modulus and strength not only maintained, even improved.展开更多
Polymer solar cells(PSCs)with high power conversion efficiency(PCE)and environment-friendly fabrication are the main requirements enabling their production in industrial scale.While the use of non-halogenated solvent ...Polymer solar cells(PSCs)with high power conversion efficiency(PCE)and environment-friendly fabrication are the main requirements enabling their production in industrial scale.While the use of non-halogenated solvent processing is inevitable for the PSC fabrication,it significantly reduces the processability of polymer donors(PDS)and small-molecule acceptors(SMAs).This often results in unoptimized blend morphology and limits the device performance.To address this issue,hydrophilic oligoethylene glycol(OEG)side-chains are introduced into a PD(2EG)to enhance the molecular compatibility between the PD and L8-BO SMA.The 2EG PD induces higher crystallinity and alleviates phase separation with the SMA compared to the reference PD(PM7)with hydrocarbon side-chains.Consequently,the 2EG-based PSCs exhibit a higher PCE(15.8%)than the PM7-based PSCs(PCE=14.4%)in the ortho-xylene based processing.Importantly,benefitted from the reduced phase separation and increased crystallinity of 2EG PDS,the 2EG-based PSCs show enhanced thermal stability(84%of initial PCE after 120 h heating)compared to that of the PM7-based PSCs(60%of initial PCE after 120 h heating).This study demonstrates the potential of OEG side-chain-incorporated materials in developing efficient,stable,and eco-friendly PSCs.展开更多
The synthesis and upconverted fluorescent properties of a series of organic compounds with the structure: donor/bridge/acceptor, and different side-chains are reported. The results show that the compounds with differe...The synthesis and upconverted fluorescent properties of a series of organic compounds with the structure: donor/bridge/acceptor, and different side-chains are reported. The results show that the compounds with different side-chains exhibit different two-photon induced fluorescent properties, although they have the same main donor/bridge/acceptor structure.展开更多
Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place ov...Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of themagnetic field.展开更多
Semiconducting two-dimensional conjugated polymers(2DCPs)with strong fluorescence emission have great potential for various optoelectronic applications.However,it is enormously challenging to achieve this goal due to ...Semiconducting two-dimensional conjugated polymers(2DCPs)with strong fluorescence emission have great potential for various optoelectronic applications.However,it is enormously challenging to achieve this goal due to the significant compact interlayerπ-πstacking-induced quenching effect in these systems.In this work,we found that highly fluorescent semiconducting 2DCPs can be prepared through an effective side-chain engineering approach in which interlayer spacers are introduced to reduce the fluorescence quenching effect.The obtained two truxene-based 2DCP films that,along with-C6H13 and-C_(12)H_(25)alkyl side chains as interlayer spacers both demonstrate superior fluorescence properties with a high photoluminescence quantum yield of 5.6%and 14.6%,respectively.These are among the highest values currently reported for 2DCP films.Moreover,an ultralong isotropic quasi-twodimensional exciton diffusion length constrained in the plane with its highest value approaching 110 nm was revealed by the transient photoluminescence microscopy technique,suggesting that theπ-conjugated structure in these truxene-based 2DCP films has effectively been extended.This work can enable a broad exploration of highly fluorescent semiconducting 2DCP films for more deeply fundamental properties and optoelectronic device applications.展开更多
The development of polymer solar cells(PSCs)for the donor materials based on benzo[1,2-b:4,5-b′]dithiophene(BDT)has significantly boosted the power conversion efficiency(PCE).However,the PCE of polymer donor material...The development of polymer solar cells(PSCs)for the donor materials based on benzo[1,2-b:4,5-b′]dithiophene(BDT)has significantly boosted the power conversion efficiency(PCE).However,the PCE of polymer donor materials for benzo[1,2-b:4,5-b′]difuran(BDF)-based lags far behind that of their BDT analogs.To further explore efficient copolymers based on BDF units,a two-dimensional(2D)side-chain strategy was proposed to investigate the atom-changing effects on the copolymer donors for the properties of electron and optical.In this study,we designed and synthesized three new BDF-based copolymer donor materials,named PBDF-C,PBDF-O,and PBDF-S.Owing to the balanced charge transport and favorable phase separation of PBDF-S:Y6,a high PCE of 13.4%,a short-circuit current(J sc)of 25.48 mA cm−2,an open-circuit voltage(V oc)of 0.721 V,and a fill factor(FF)of 72.6%was obtained.This research demonstrates that the BDF building block has great potential for constructing conjugated copolymer donors for high-performance PSCs and that 2D side-chain modification is a facile approach for designing high-performance BDF-based copolymer materials.展开更多
Controlling the aggregation of small-molecule acceptors(SMAs)is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells(PSCs).However,reducing intermolecular aggreg...Controlling the aggregation of small-molecule acceptors(SMAs)is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells(PSCs).However,reducing intermolecular aggregation of SMAs is usually accompanied by the disruption of compact molecular packing thereby leading to their decreased electron mobilities.Here,two novel M-series SMAs(MD1T and MD2T)based on ladder-type heterononacenes with neighboring side-chains separated by one or two thiophene rings are designed and synthesized.It is found that shortening the spacing of the neighboring side-chains of the SMAs can greatly alleviate the intermolecular aggregation and alter the molecular orientation from bimodal edge-on/face-on to predominant face-on while maintaining the compact molecular packing.As a result,a more favorable morphology with smaller domain sizes is formed for the MD1T-based blend films,which greatly improves the charge generation and charge transport for the corresponding PSCs.The best-performing MD1T-based device affords an efficiency of 12.43%,over seven times higher than that of the MD2T-based device.This work reveals the importance of the spacing between the neighboring side-chains in modulating the molecular aggregation and active layer morphology,and the obtained structure-performance relationships shall provide important guidance for designing highly efficient SMAs.展开更多
Chemical synthesis of peptides and proteins has evolved into an indispensable tool for chemical biology. Peptide ligation is a straightforward technique for joining two short peptide fragments together via a native pe...Chemical synthesis of peptides and proteins has evolved into an indispensable tool for chemical biology. Peptide ligation is a straightforward technique for joining two short peptide fragments together via a native peptide bond to afford a larger natural peptide or protein. However, the junction sites are limited to several specific amino acids because most peptide ligations involve participation of the side-chain functional groups of the junction-site amino acids. To overcome such intrinsic limitations, "general"peptide ligations which do not rely on the side-chain functional group have been developed. This review summarized the recent developments in peptide ligations that are independent of side-chain functional group of ligation-junction-site amino acid.展开更多
A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3'-di(3",5"-dimethylphenyl)-4,4'-difluorodiphenyl su...A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3'-di(3",5"-dimethylphenyl)-4,4'-difluorodiphenyl sulfone and other commercial monomers via polycondensation reaction, and subsequent bromination, quaternization and alkalization. The chemical structures of the ionomers were confirmed by 1H- and 13C-NMR spectroscopy. Water uptake, swelling ratio, hydroxide conductivity, the number of bonded water per ammonium group (A), volumetric ion exchange capacity (IECvwet), mechanical and thermal properties, and chemical stability were systematically evaluated for the series of QTBMs membranes. QTBMs showed IECs ranging from 1.02 meq·g-1 to 2.11 meq·g-1; in particular, QTBM-60 membrane with the highest IEC (2.11 meq·g-1) had very high hydroxide ion conductivity of 131.9 mS·cm-1 at 80 ℃, which was attributed to the well assembled nano-channels with distinct phase separation evidenced by small-angle X-ray scattering (SAXS). It was found that the hydrated QTBMs membranes were mechanically stable with moderate water uptakes and swelling ratios, high chemical stability under the harsh alkaline conditions. This work provides a facile way to prepare anion exchange membranes (AEMs) with high performances for the application in alkaline fuel cells.展开更多
In this work, four fused ring electron acceptors(FREAs), 2F-C5, 2F-C6, 2F-C8 and 2F-C10, are developed to investigate the effect of side-chain size on the molecular properties and photovoltaic performance of FREA syst...In this work, four fused ring electron acceptors(FREAs), 2F-C5, 2F-C6, 2F-C8 and 2F-C10, are developed to investigate the effect of side-chain size on the molecular properties and photovoltaic performance of FREA systematically. The elongation of side-chains in the FREAs not only improves their solubility in the processing solvent, but also enhances their miscibility with the donor PBDB-T. It helps the FREA diffuse into the donor PBDB-T during film-formation, thus leading to the decrease in domain size and domain purity from PBDB-T:2F-C5 to PBDB-T:2F-C10 blend films in sequence. The smaller domain size affords more D/A interfaces to benefit exciton dissociation and inhibit monomolecular recombination. However, severe bimolecular recombination occurs when the domain purity decreases to a critical point. Due to the dual function of the increment of side-chain length, both short-circuit current density(J_(SC)) and fill factor(FF) of devices exhibit an evolution of first increasing then decreasing from 2F-C5, 2F-C6, 2F-C8 to 2F-C10 based OSCs. The PBDB-T:2F-C8 based OSCs get a fine balance in morphology with moderate domain size as well as high domain purity simultaneously for the least charge carrier recombination, thus achieving the highest power conversion efficiency of 12.28% with the best J_(SC)(21.27 mA cm^(-2)) and FF(71.96%).展开更多
Long-alkyl tail triphenylene (TP) side-chain liquid crystalline polymers (SCLCPs) with different spacer length (P-m-TP, m = 2, 3, 4, 6, 8, which is the number of carbon atom in the flexible alkyl spacers) have b...Long-alkyl tail triphenylene (TP) side-chain liquid crystalline polymers (SCLCPs) with different spacer length (P-m-TP, m = 2, 3, 4, 6, 8, which is the number of carbon atom in the flexible alkyl spacers) have been successfully synthesized via free radical polymerization. The differential scanning calorimetry (DSC), polarized light microscopy (POM), ultraviolet-visible spectroscopy (UV- Vis), wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements were performed to investigate the influence of multiple effects on the self-organization behaviors of P-m-TP, including steric effect, decoupling effect and π-π stacking effect. The experimental results revealed that P-m-TP (m = 2, 3, 4) formed the columnar phase which was developed by the TP moieties and the main chain as a whole, suggesting that the side-chains had strong steric effect even though the number of spacer length (m) exceeded 4. In addition, the clearing points (Tis) of the polymers were above 300 ℃. When m = 6 and 8, the polymers displayed hexagonal columnar phase and exhibited the low Tis (91 and 80 ℃ respectively), originating from the self-assembly of triphenylene due to the decoupling effect and π-π stacking effect. This work offers a viable and inspiring pathway to control the phase transition temperature and phase structure ofTP SCLCPs via simply tailoring the spacer length and increasing the alkyl tail length of TP.展开更多
基金Supported by the National Natural Science Foundation of China(#91534115).
文摘Side-chain alkylation of toluene with methanol is a green pathway to realize the one-step production of styrene under mild conditions,but the low selectivity of styrene is difficult to be improved with by-products of ethylbenzene and xylene.In this study,a new way is introduced to improve the catalytic performance by means of assisting basic compounds as co-catalysts during the toluene side-chain alkylation with methanol to styrene.As a result,high activity of side-chain alkylation appears over the basic Cs-modified zeolite catalysts prepared by ion exchange and impregnation methods.This high performance should be mainly attributed to two co-catalysis actions:(1)the promotion of basic compounds for methanol dehydrogenation to formaldehyde as the intermediate for side-chain alkylation;(2)the suppression of the styrene transfer hydrogenation on basic Cs-modified zeolites to avoid the formation of ethylbenzene.Especially for Cs_(2)O/CsX-ex catalyst,the addition of 2%mol/mol 2-picoline in reaction mixture could achieve both 12.3%toluene conversion and 84.1%styrene selectivity.Whereas the higher concentration of 2-picoline(>6%mol/mol)caused an inhibition to the catalytic activity because the excessive basic compound poisoned the combined acid-base pathway required for the side-chain alkylation process.In addition,two possible side-chain alkylation reaction routes on Cs-modified zeolite under the different 2-picoline absorption were described.
基金This project was in part supported by the Hong Kong Research Grants Council(HKUST597/95P&6149/97P)
文摘A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized,whose mesomorphic properties are found to be easily 'tunab1e' by simple mechanical perturbation. Thepolymerization of 10- [ 4 - (4' -methoxyphenoxycarbonyl )phenoxycarbonyl] - 1 -decyne (4 ) in itiated by theWCl_6-Ph_4Sn/dioxane complex yields polymer 5 with a M_w of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.
基金the Natural Science Foundation of Chongqing(cstc2019jcyj-msxmX0400)Youth Innovation Promotion Association Chinese Academy of Sciences(2020379)+2 种基金Chongqing Funds for Distinguished Young Scientists(cstc2020jcyj-jqX0018)General Program of National Natural Science Foundation of China(62074149)National Natural Science Foundation of China(51961165102).
文摘Side-chain modification is a proven effective approach for morphology manipulation in organic solar cells(OSCs).However,in-depth analysis and investigation involving side-chain modification towards morphology improvement,including molecular microstructure,orientating packing and aggregation are urgent for all-small-molecule(ASM)systems.Herein,employing a fluorine-modified two-dimension benzodithiophene(BDT)as central unit,we contrastively synthesized two small-molecule donors,namely BDT-F-SR and BDT-F-R,each welding alkylthio side-chains on thienyl of central BDT unit and the other grafted non-sulfuric alkyl side-chains.As predicted,the synergetic side-chain modification of fluorination and alkyl changeover triggers diverse molecular dipole moments and orientations,resulting in different molecular energy levels,thermal stabilities,molecular planarity and order.Eventually,together with the preeminent small-molecule acceptor Y6,BDT-F-R-based ASM OSCs obtain enhanced power conversion efficiency(PCE)of 13.88%compared to BDT-F-SR-based devices(PCE of 12.75%)with more suitable phase-separation and balanced carrier mobilities.The contrast results reveal that alkyl sidechains seem to be a more satisfactory partner for fluorine-modified 2D BDT-based small-molecule donors compared to alkylthio pendants,and highlight the significance of subtle side-chain modification for molecular structural order fun-tuning and morphology control,laying the foundation for efficient ASM OSCs.
文摘The morphological changes of a side-chain liquid-crystalline polymethacrylate during isotropization and liquid-crystallization transitions were studied by means of polarizing microscopy. These transitions were found to be composed of the initiation of a new phase at local places of the old phase matrix and the growth of the new phase: domains. The kinetics of the liquid-crystallization of the polymer from an isotropic melt to a smectic mesophase was also investigated. The isothermal process of the transition can be described by the Avrami equation. The values of the Avrami exponent were found to be around 2.6. which is lower than the value usually obtained for crystallization transition of polymers, but larger than that reported for liquid-crystallization transition of main-chain polymers. These results may indicate the difference in growth geometry of new phase during transition between crystallization and liquid-crystallization in general and between liquid-crystallization of main-chain and side-chain polymers. It was found that the liquid-crystallization of the used side-chain polymethacrylate may occur at small undercoolings with high transformation rate similar to that of main-chain polymers and small-molecule liquid crystals, while the crystallization of polymers can only proceed at large undercoolings. These phenomena can be explained by the idea that the surface free energy of nucleus during liquid-crystallization transition is less than that for crystallization, and evidence was obtained from analysis of the temperature dependence of the transformation rate.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60478013, 20571089 and 10274107), the Natural Science Foundation of Guangdong Province, China (Grant No 05101819), and the Doctoral Program Foundation of Institute of Higher Education of China(Grant No 20040558031).
文摘Photoluminescence properties and exciton decay dynamics in a porphyrin side-chain polymer, poly[porphyrin acrylate- acrylonitrile (abbreviated p[(por)A-AN]), have been investigated by femtosecond time-resolved photoluminescence spectroscopy. All the luminescences of p[(por)A-AN] films are due to the emissive decay of the photoexcited singlet excitons in the porphyrins. The luminescence efficiencies and lifetimes are increased for samples from pure films to dilute blend films. However, they are increased as the intrachain concentration of the porphyrin sidechain groups is decreased. The intrachain rotation motions of porphyrin sidechain groups result in the initial ultrafast luminescence decays, which are much faster than those due to the interchain interactions. All the samples show no significant red-shift and broadening of the transient luminescence spectra. The interchain and intrachain nonradiative exciton relaxation processes may play an important role in the luminescence dynamics in the p[(por)A-AN] films. The possible origin of different intrachain and interchain dynamic behaviours in p[(por)A-AN] films is discussed.
基金The authors are grateful to the Director Foundation of Institute of Chemistry,Chinese Academy of Sciences and Science Foundation of Polymer Physics Laboratory,Chinese Academy of Sciences for supporting this work
文摘The morphological features of a side-chain liquid crystalline polymer during the mesophase transitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogens of three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture was observed in the transition temperature range. Similar to main-chain liquid crystalline polymers the transition process of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local places of the old phase matrix and a growth process of the new phase domains.
基金We are grateful to the National Natural Science Foundation of China for financial support(project No.20274026)
文摘This is a part of our systematic research work on polyimides with mesogenic unit side chain. In this study, a new 4'-phenylpbenyl 4-(3",5"-diaminobenzoyloxy)benzoate and polyimide were synthesized, and characterized by FTIR, ^1H-NMR, inherent viscosity, mechanical properties, and solubility measurements. The diamine composed with mesogenic unit aryl ester groups and bipbenyl group with longer L/D ratio, was synthesized by two key steps. Firstly, the hydroxy group of 4-hydroxybenzoic acid was protected by acetoxy group for avoiding self- polymerization of 4-hydroxybenzoic acid, and then selectively hydrolyzed after esterification of carboxyl. Secondly, a selective catalysis hydrogenation was adopted to prevent the aryl ester from deoxidation. Based on this diamine, a novel polyimide was prepared by polycondensation of 4'-phenylphenyl 4-(3", 5"-diaminobenzoyloxy)benzoate and 4-aminophenyl ether(ODA) with 4, 4'-oxydiphthalic anhydride(ODPA) in N-methyl-2-pyrrolidone (NMP). The resulting polyimide with longer side chain showed better solubility and more regular structure. Its inherent viscosity is lower than that without side chains, but its modulus and strength not only maintained, even improved.
基金Korea Institute of Energy Technology Evaluation and Planning(KETEP)grant(20214000000650)National Research Foundation(NRF)grant(2022R1A2B5B03001761)funded by the Korea government.
文摘Polymer solar cells(PSCs)with high power conversion efficiency(PCE)and environment-friendly fabrication are the main requirements enabling their production in industrial scale.While the use of non-halogenated solvent processing is inevitable for the PSC fabrication,it significantly reduces the processability of polymer donors(PDS)and small-molecule acceptors(SMAs).This often results in unoptimized blend morphology and limits the device performance.To address this issue,hydrophilic oligoethylene glycol(OEG)side-chains are introduced into a PD(2EG)to enhance the molecular compatibility between the PD and L8-BO SMA.The 2EG PD induces higher crystallinity and alleviates phase separation with the SMA compared to the reference PD(PM7)with hydrocarbon side-chains.Consequently,the 2EG-based PSCs exhibit a higher PCE(15.8%)than the PM7-based PSCs(PCE=14.4%)in the ortho-xylene based processing.Importantly,benefitted from the reduced phase separation and increased crystallinity of 2EG PDS,the 2EG-based PSCs show enhanced thermal stability(84%of initial PCE after 120 h heating)compared to that of the PM7-based PSCs(60%of initial PCE after 120 h heating).This study demonstrates the potential of OEG side-chain-incorporated materials in developing efficient,stable,and eco-friendly PSCs.
基金This work was supported by thc grant for State Key Program of Chinaby the National Natural Science Foundation of China.
文摘The synthesis and upconverted fluorescent properties of a series of organic compounds with the structure: donor/bridge/acceptor, and different side-chains are reported. The results show that the compounds with different side-chains exhibit different two-photon induced fluorescent properties, although they have the same main donor/bridge/acceptor structure.
文摘Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate(P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown thatthe magnetic alignment takes place over the entire temperature range between its meltingpoint and clearing point and the orientation level is strongly temperature-dependent, thedevelopment with time of the magnetic orieatation follows an exponeotial-type relation,and the smectic phase state influences the thermal relaxation process in the absence of themagnetic field.
基金supported by the Ministry of Science and Technology of China(grant nos.2018YFA0703200 and 2022YFB3603800)the Natural Science Foundation of China(grant nos.21875259,52233010,51725304,61890943,and 22021002)+3 种基金the CAS Project for Young Scientists in Basic Research(grant no.YSBR-053)the Youth Innovation Promotion Association of the Chinese Academy of Sciences,the National Program for Support of Top-notch Young Professionals,the Beijing National Laboratory for Molecular Sciences(grant no.BNLMS-CXXM-202012)the Key Research Program of the Chinese Academy of Sciences(grant no.XDPB13)K.C.Wong Education Foundation(grant no.GJTD-2020-02).
文摘Semiconducting two-dimensional conjugated polymers(2DCPs)with strong fluorescence emission have great potential for various optoelectronic applications.However,it is enormously challenging to achieve this goal due to the significant compact interlayerπ-πstacking-induced quenching effect in these systems.In this work,we found that highly fluorescent semiconducting 2DCPs can be prepared through an effective side-chain engineering approach in which interlayer spacers are introduced to reduce the fluorescence quenching effect.The obtained two truxene-based 2DCP films that,along with-C6H13 and-C_(12)H_(25)alkyl side chains as interlayer spacers both demonstrate superior fluorescence properties with a high photoluminescence quantum yield of 5.6%and 14.6%,respectively.These are among the highest values currently reported for 2DCP films.Moreover,an ultralong isotropic quasi-twodimensional exciton diffusion length constrained in the plane with its highest value approaching 110 nm was revealed by the transient photoluminescence microscopy technique,suggesting that theπ-conjugated structure in these truxene-based 2DCP films has effectively been extended.This work can enable a broad exploration of highly fluorescent semiconducting 2DCP films for more deeply fundamental properties and optoelectronic device applications.
基金supported by the National Natural Sci-ence Foundation of China(Grant Nos.51825301 and 52022099)China Postdoctoral Science Foundation(BX20190023)H.Y.W acknowl-edges the financial support of the National Research Foundation of Ko-rea(2019R1A6A1A11044070).
文摘The development of polymer solar cells(PSCs)for the donor materials based on benzo[1,2-b:4,5-b′]dithiophene(BDT)has significantly boosted the power conversion efficiency(PCE).However,the PCE of polymer donor materials for benzo[1,2-b:4,5-b′]difuran(BDF)-based lags far behind that of their BDT analogs.To further explore efficient copolymers based on BDF units,a two-dimensional(2D)side-chain strategy was proposed to investigate the atom-changing effects on the copolymer donors for the properties of electron and optical.In this study,we designed and synthesized three new BDF-based copolymer donor materials,named PBDF-C,PBDF-O,and PBDF-S.Owing to the balanced charge transport and favorable phase separation of PBDF-S:Y6,a high PCE of 13.4%,a short-circuit current(J sc)of 25.48 mA cm−2,an open-circuit voltage(V oc)of 0.721 V,and a fill factor(FF)of 72.6%was obtained.This research demonstrates that the BDF building block has great potential for constructing conjugated copolymer donors for high-performance PSCs and that 2D side-chain modification is a facile approach for designing high-performance BDF-based copolymer materials.
基金National Natural Science Foundation of China,Grant/Award Numbers:52130306,22075287,22101285Program of Youth Innovation Promotion Association CAS,Grant/Award Number:2021299。
文摘Controlling the aggregation of small-molecule acceptors(SMAs)is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells(PSCs).However,reducing intermolecular aggregation of SMAs is usually accompanied by the disruption of compact molecular packing thereby leading to their decreased electron mobilities.Here,two novel M-series SMAs(MD1T and MD2T)based on ladder-type heterononacenes with neighboring side-chains separated by one or two thiophene rings are designed and synthesized.It is found that shortening the spacing of the neighboring side-chains of the SMAs can greatly alleviate the intermolecular aggregation and alter the molecular orientation from bimodal edge-on/face-on to predominant face-on while maintaining the compact molecular packing.As a result,a more favorable morphology with smaller domain sizes is formed for the MD1T-based blend films,which greatly improves the charge generation and charge transport for the corresponding PSCs.The best-performing MD1T-based device affords an efficiency of 12.43%,over seven times higher than that of the MD2T-based device.This work reveals the importance of the spacing between the neighboring side-chains in modulating the molecular aggregation and active layer morphology,and the obtained structure-performance relationships shall provide important guidance for designing highly efficient SMAs.
基金supported by the National Natural Science Foundation of China (21462023), and the Natural Science Foundation of Jiangxi Province (20143ACB20007, 20153BCB23018)
文摘Chemical synthesis of peptides and proteins has evolved into an indispensable tool for chemical biology. Peptide ligation is a straightforward technique for joining two short peptide fragments together via a native peptide bond to afford a larger natural peptide or protein. However, the junction sites are limited to several specific amino acids because most peptide ligations involve participation of the side-chain functional groups of the junction-site amino acids. To overcome such intrinsic limitations, "general"peptide ligations which do not rely on the side-chain functional group have been developed. This review summarized the recent developments in peptide ligations that are independent of side-chain functional group of ligation-junction-site amino acid.
基金supported by the National Natural Science Foundation of China(No.51173045)Student Research Program(SRP) Funds of South China University of Technology(Nos.105612015S165 and 105612016S198)
文摘A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3'-di(3",5"-dimethylphenyl)-4,4'-difluorodiphenyl sulfone and other commercial monomers via polycondensation reaction, and subsequent bromination, quaternization and alkalization. The chemical structures of the ionomers were confirmed by 1H- and 13C-NMR spectroscopy. Water uptake, swelling ratio, hydroxide conductivity, the number of bonded water per ammonium group (A), volumetric ion exchange capacity (IECvwet), mechanical and thermal properties, and chemical stability were systematically evaluated for the series of QTBMs membranes. QTBMs showed IECs ranging from 1.02 meq·g-1 to 2.11 meq·g-1; in particular, QTBM-60 membrane with the highest IEC (2.11 meq·g-1) had very high hydroxide ion conductivity of 131.9 mS·cm-1 at 80 ℃, which was attributed to the well assembled nano-channels with distinct phase separation evidenced by small-angle X-ray scattering (SAXS). It was found that the hydrated QTBMs membranes were mechanically stable with moderate water uptakes and swelling ratios, high chemical stability under the harsh alkaline conditions. This work provides a facile way to prepare anion exchange membranes (AEMs) with high performances for the application in alkaline fuel cells.
基金supported by the National Postdoctoral Program for Innovative Talents (BX201700253)the China Postdoctoral Science Foundation (2017M620068, 2018M630208)+1 种基金the National Natural Science Foundation of China (21673257, 21805288)the Ministry of Science and Technology (2016YFA0200700)
文摘In this work, four fused ring electron acceptors(FREAs), 2F-C5, 2F-C6, 2F-C8 and 2F-C10, are developed to investigate the effect of side-chain size on the molecular properties and photovoltaic performance of FREA systematically. The elongation of side-chains in the FREAs not only improves their solubility in the processing solvent, but also enhances their miscibility with the donor PBDB-T. It helps the FREA diffuse into the donor PBDB-T during film-formation, thus leading to the decrease in domain size and domain purity from PBDB-T:2F-C5 to PBDB-T:2F-C10 blend films in sequence. The smaller domain size affords more D/A interfaces to benefit exciton dissociation and inhibit monomolecular recombination. However, severe bimolecular recombination occurs when the domain purity decreases to a critical point. Due to the dual function of the increment of side-chain length, both short-circuit current density(J_(SC)) and fill factor(FF) of devices exhibit an evolution of first increasing then decreasing from 2F-C5, 2F-C6, 2F-C8 to 2F-C10 based OSCs. The PBDB-T:2F-C8 based OSCs get a fine balance in morphology with moderate domain size as well as high domain purity simultaneously for the least charge carrier recombination, thus achieving the highest power conversion efficiency of 12.28% with the best J_(SC)(21.27 mA cm^(-2)) and FF(71.96%).
基金financially supported by the National Natural Science Foundation of China (No.21504075)Natural Science Foundation of Hunan Province (No.2017JJ3294)
文摘Long-alkyl tail triphenylene (TP) side-chain liquid crystalline polymers (SCLCPs) with different spacer length (P-m-TP, m = 2, 3, 4, 6, 8, which is the number of carbon atom in the flexible alkyl spacers) have been successfully synthesized via free radical polymerization. The differential scanning calorimetry (DSC), polarized light microscopy (POM), ultraviolet-visible spectroscopy (UV- Vis), wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements were performed to investigate the influence of multiple effects on the self-organization behaviors of P-m-TP, including steric effect, decoupling effect and π-π stacking effect. The experimental results revealed that P-m-TP (m = 2, 3, 4) formed the columnar phase which was developed by the TP moieties and the main chain as a whole, suggesting that the side-chains had strong steric effect even though the number of spacer length (m) exceeded 4. In addition, the clearing points (Tis) of the polymers were above 300 ℃. When m = 6 and 8, the polymers displayed hexagonal columnar phase and exhibited the low Tis (91 and 80 ℃ respectively), originating from the self-assembly of triphenylene due to the decoupling effect and π-π stacking effect. This work offers a viable and inspiring pathway to control the phase transition temperature and phase structure ofTP SCLCPs via simply tailoring the spacer length and increasing the alkyl tail length of TP.