查看更多>>摘要：Copper(0)-mediated reversible-deactivation radical polymerization(Cu(0)-mediated RDRP)of the water-soluble monomer N-isopropylacrylamide(NIPAM)has been challenging with the problems of high dispersity,poor control over the molecular weights(MWs)or complex or multi reaction steps,etc.In this work,we report the well-controlled polymerization of NIPAM in water via a facile one-pot and one-step Cu(0)-mediated RDRP.The results of this approach show that the key for kicking off the Cu(0)-mediated NIPAM RDRPs is to ensure sufficient CuⅠ at the very beginning,and the key to achieve a well-controlled chain growth is to provide adequate deactivation strength during the polymerization process.For NIPAM,which has a high propagation rate constant,the deactivation control can be effectively enhanced by extra adding deactivator(i.e.,CuⅡ)to the system.Moreover,a low reaction temperature(4 ℃)is necessary in the controlled synthesis of higher MW poly(N-isopropylacrylamide)(PNIPAM)to avoid the compromise in control caused by the phase transition from its lower critical solution temperature(LCST).Through this new kinetically controlled strategy,PNIPAMs with well-defined structure,narrow molecular weight distributions(MWDs)and varied MWs were successfully achieved.
查看更多>>摘要：This work reported an AIE fluorescent probe for tumor imaging based on the pH induced self-assembly strategy.The fluorescent probe was composed of an acid-responsive soluble copolymer PEG-b-PAMA-DMMA with a maleic acid amide group and an anionic soluble aggregation-induced emission fluorogen(AIEgen)TPE-2SO3-.The polymer could be transformed into a protonated amine-containing polymer after the hydrolysis of maleic acid amide in acidic tumor microenvironment,which would be further self-assembled with TPE-2SO3-to form aggregated nanoparticles.The transition of TPE-2SO3-from dispersed state to aggregated state led to an obvious increase in fluorescence intensity due to its AIE characteristics.
查看更多>>摘要：Regioregular poly(3-hexylthio)thiopene(P3HTT)has emerged tremendous potential in organic electronic applications due to the strong noncovalent interactions from the sulfur atom linked to thiophene.However,P3HTT generally exhibits low charge mobility mostly due to poor solution processability attributed to dense arrangement of hexylthio side chain in polymer,which led to strong noncovalent interactions among sulfur atoms.To balance the nonvalent interaction and aggregation for P3HTT,herein,we systematically study the effect of hexylthio side chain content in polymer backbone on the structure and properties.A series of regioregular P3HTT-based homopolymers(P3HTT,P3HTT-50,P3HTT-33 and P3HTT-25)were prepared via Kumada catalyst transfer polycondensation method from a set of mono-,bi-,ter-and quarter-thiophenes containing different contents of hexylthio side chain.The DFT calculation shows the planarity of polymers backbone could be improved through reducing the density of hexylthio side chain in polymer mainchain.And significant changes in their crystallinity,aggregation and optical properties were observed with the content of hexylthio side chain reducing.The P3HTT-33 displayed the highest field-effect transistor hole mobility of 2.83×10-2 cm2.V-1.s-1 resulting from a balance between the crystallinity and planarity.This study demonstrates modulating the content of hexylthio side chain in P3HTT is an effective strategy to optimize the opto-electronic properties of polymer obtaining excellent semiconductor device performance.
查看更多>>摘要：Developing new polymeric semiconductors with excellent device performance is essential for organic electronics.Herein,we synthesized two new thiazoloisoindigo(Tzll)-based polymers,namely,P(Tzll-dTh-dTh)and P(Tzll-dTh-dTz),by copolymerizing thiophene-flanked Tzll with bithiophene and bithiazole,respectively.Owing to the more electron-deficient nature of bithiazole than bithiophene,P(Tzll-dTh-dTz)possesses deeper LUMO/HOMO levels of-3.45/-5.47 eV than P(Tzll-dTh-dTh)(-3.34/-5.32 eV).The organic field-effect transistor(OFET)devices based on P(Tzll-dTh-dTh)exhibited p-type behaviors with an average hole mobility value as high as 1.43 cm2·V-1·s-1,while P(Tzll-dTh-dTz)showed typical ambipolar characteristics with average hole and electron mobilities of 0.38 and 0.56 cm2.V-1·s-1.In addition,we compared the performances of both polymers with other Tzll-based polymers reported in our previous work,and showed that the charge carrier polarity can be manipulated by adjusting the number of the thiophene units between the acceptor unit.As the increase of the number of thiophene rings,charge carrier polarity shifts from electron-dominated ambipolar transport to hole-dominated ambipolar transport and then to unipolar hole transport in OFETs,which provides an effective molecular design strategy for further optimization of polymer OFET performance.
查看更多>>摘要：The highly efficient method has been developed for the synthesis of NHC·VOCl3 containing symmetrical or unsymmetrical N-heterocyclic carbene(NHC)ligands by the transmetallation reaction of NHC·AgCl with VOCl3.The total isolated yield of VOCl3[1,3-(2,4,6-Me3C6H2)2(NCH=)2C:](V4')reached 86％by transmetallation reaction,which is much higher than that(48％)by direct coordination method.This methodology has also been used to synthesize the novel vanadium complexes containing unsymmetrical NHC ligands of VOCl3[PhCH2NCH=CHNR)C:](V5',R=2,4,6-Me3C6H2;V6',R=2,4-Me2-6-Ph-C6H2;V7',R=2,6-iPr2-C6H3)with high yield,which could not be obtained by direct coordination method.The catalytic activity and copolymerization ability would be improved by introducing unsymmetrical NHC ligands due to their less steric bulky effect.The vanadium complex V5'containing unsymmetrical NHC ligand exhibits higher catalytic activity(3.7×105 gcopolymer·mol-1 of V·h-1)than that of V4'containing symmetrical NHC ligand.Moreover,the higher propylene incorporation ratio(45.6 mol％)in the copolymers of ethylene with propylene could be obtained by using V5'than that(39.9％)by using V4'.The results would provide a highly efficient strategy for the synthesis of early transition metal complexes containing versitile NHC ligands,affording the catalyst with both high catalytic activity and copolymerization ability for the synthesis of high performance polyolefin elastomers.
查看更多>>摘要：A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl)metallocene complexes(Zr:1-5;Hf:6)have been synthesized,characterized and investigated as catalyst precursors for the high temperature ethylene polymerization.Using methylaluminoxane(MAO)as the cocatalyst,zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×107 gPE·molZr-1·h-1 toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49x105-6.31x105 g/mol),meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h.By adopting low Al/Zr ratios,such as 125,polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained.It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities,which increased rapidly with the increase of polymerization temperature,thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures.In contrast to zirconocene complexes 1-5,hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5.Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures,but only afforded waxes with low molecular weights.
查看更多>>摘要：A series of Ti(Ⅳ)dichloride and dialkoxide complexes with phenoxyimine ligands containing fluorinated and nonfluorinated aliphatic imine fragments have been synthesized.The molecular structures of complexes 1 and 4 were established by single-crystal X-ray diffraction studies.The complexes adopt a distorted octahedral coordination structure around the titanium atom and two oxygen atoms are situated in trans position while two nitrogen atoms and two outgoing ligands(Cl or iPrO)are situated in cis position.Effect of activators(MMAO-12 and combinations EtnAlCl3-n+Bu2Mg)and outgoing ligand(Cl or iPrO)nature on the catalytic activity and properties of the resulting polymers was studied.The Ti complexes,despite the nature of the outgoing ligands(Cl or iPrO)in the presence of Al/Mg activators,was found to display a high ethylene polymerization activity in the range 1600-3830 kgpolymer·molTi-1·h-1·atm-1 with a viscosity average molecular weight(Mv)value in the range 1.1x106-7.1x106 Dalton(Da).The resulting UHMWPE can be processed by a solventless method into high-strength and high-modulus oriented films.The rheological characteristics of a polymer melt have been studied.The absence of a cross-over point did not allow to compare the values of the molecular weight distribution of polymers obtained on fluorinated and non-fluorinated pre-catalysts,however,the estimation of the entanglement density is in good agreement with the mechanical characteristics of oriented films.Upon activation with methylalumoxane,the activity of the complexes decreased very significantly;however,a polymer with a molecular weight of about 12 million Da was obtained.In the process of ethylene/octene-1 copolymerization,fluorine-containing precatalysts showed a clear advantage over non-fluorinated analogues both in activity and in comonomer content.
查看更多>>摘要：It is of great significance to design epoxy coatings with superior antibacterial properties and high adhesive properties,as well as excellent processing,superior durability,and high transparency.However,it is still a challenge because of the common complex design and synthesis.Herein,the bio-based monomer protocatechuic acid(PCA)was used as raw material,the catechol structure with high bonding and antibacterial properties was introduced into the flexible alkane segment of ethylene glycol diglycidyl ether(EGDE)through an efficient,and green method,and it was cured with isophorone diamine(IPDA)to prepare corresponding thermosets.The cured resins exhibited excellent all-around qualities,particularly in bonding and antibacterial.When 30％PCA was added to pure epoxy resin,the adhesion between substrate and coating increased from 4.40 MPa to 13.60 MPa and the antibacterial rate of coating against E.coli and S.aureus could approach 100％.All of this is due to the fact that the catechol structure present in PCA has the ability to interact with various substrates and alter the permeability of bacterial cell membranes.The architecture of this method offers a fresh approach to dealing with the issues of challenging raw material selection and complex synthesis techniques.
查看更多>>摘要：The emerging biomass-based epoxy vitrimers hold great potential to fulfill the requirements for sustainable development of society.Since the existence of dynamic chemical bonds in vitrimers often reduces both the thermal and mechanical properties of epoxy resins,it is challenging to produce recyclable epoxy vitrimers with both excellent mechanical properties and good thermal stability.Herein,a monomer 4-(((5-(hydroxymethyl)furan-2-yl)methylene)amino)phenol(FCN)containing furan ring with potential to form high density of hydrogen bonding among repeating units is designed and copolymerized with glycerol triglycidyl ether to yield epoxy resin(FCN-GTE),which intrinsically has dual hydrogen bond networks,dynamic imine structure and resultant high performance.Importantly,as compared to the BPA-GTE,the FCN-GTE exhibits significantly improved mechanical properties owing to the increased density of hydrogen bond network and physical crosslinking interaction.Furthermore,density functional theory(DFT)calculation and in situ FTIR analysis is conducted to decipher the formation mechanism of hydrogen bond network.In addition,the FCN-GTE possesses superior UV shielding,chemical degradation,and recyclability because of the existence of abundant imine bonds.Notably,the FCN-GTE-based carbon fiber composites could be completely recycled in an amine solution.This study provides a facile strategy for synthesizing recyclable biomass-based high-performance epoxy vitrimers and carbon fiber composites.
查看更多>>摘要：Thermoplastic polycarbonate polyurethanes(PCUs)are multiblock copolymers that have been applied for medical devices for long time.Aliphatic diols are common chain extenders(CE)involved in the composition of the hard segments of PCU.However,limited knowledge was discovered about how the chemical structure of CE affects the hydrogen bonding organization within PCUs and their mechanical properties.To investigate this problem,a group of PCUs were synthesized respectively by extending the polymer chain with 1,4-butanediol(BDO),aminoethanol(MEA),ethanediol(EO)as three kinds of chain extenders.Tiny differences in the CE chemical structure results in remarkable variations in phase separation,condensed morphologies,thermal and mechanical properties,which are characterized by Fourier transform infrared spectrometer,atomic force microscopy,small-angle X-ray scattering,differential scanning calorimetry,and tensile tests.The microstructural evolution during unilateral deformation and the different mechanism induced by the different CEs was probed and unveil by in situ wide-and small-angle X-ray diffraction.Symmetry of CE can improve the organization of the hydrogen bonding.The coherence strength of the urethane/urea group also plays a key role by comparing the two PCUs with ethanediol and aminoethanol.
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