The n-channel behavior has been occasionally reported in the organic field-effect transistors （OFETs） that usually exhibit p-channel transport only. Reconfirmation and further examination of these unusual device per...The n-channel behavior has been occasionally reported in the organic field-effect transistors （OFETs） that usually exhibit p-channel transport only. Reconfirmation and further examination of these unusual device performances should deepen the understanding on the electron transport in organic semiconductors. 6,13-bis（triisopropyl-silylethynyl） pentacene （TIPS-pentacene）, a widely examined p-channel material as Au is used for source-drain electrodes, has recently been reported to exhibit electron transport when grown from non-polar solvent on divinyltetramethyldisiloxanebis （benzocy- clobutene） （BCB） dielectric, spurring the study on this unusual electron transport. This paper describes FET characteristics of solution-grown TlPS-pentacene single crystals on five polymer gate dielectrics including polystyrene （PS）, poly（methyl methacrylate） （PMMA）, poly（4-vinyl phenol） （PVP）, poly（vinyl alcohol） （PVA） and poly（vinylidene fluoride-trifluoroethylene-chlorofluoroethylene） （P（VDF-TrFE-CFE））. In addition to the p-channel behavior, electron transport occurs in the crystals on PMMA, PS, thick PVA （40 nm） and a bilayer dielectric of PMMA on P（VDF-TrFE-CFE）, while does not on PVP and thin PVA （2 nm）. The two distinct FET characteristics are consistent with the previous reported trap effect of hydroxyl groups （in PVP and PVA） and reduced injection barrier by Na~ ions （as impurity in PVA）. The highest electron mobility of 0.48 cm2 V-1 s-1 has been achieved in the crystals on PMMA. Furthermore, the electron transport is greatly attenuated after the crystals are exposed to the vapor of a variety of polar solvents and the attenuated electron transport partially recovers if the crystals are heated, indicating the adverse effect of polar impurities on electron transport. By reconfirming the n-channel behavior in the OFETs based on TIPS-pentacene, this work has implications for the design of n-channel and ambipolar OFETs.展开更多
An novel compounding process using nano-CaCO_(3) aqueous suspension for preparing polymer/nano-CaCO_(3) composites with nanoparticles dispersed at the nanoscale is reported.The process is called the mild mixing method...An novel compounding process using nano-CaCO_(3) aqueous suspension for preparing polymer/nano-CaCO_(3) composites with nanoparticles dispersed at the nanoscale is reported.The process is called the mild mixing method.In this method,the pre-dispersed nano-particle suspensions are blended with melting polymers in a weak shearing field using an extruder,followed by removing the water from the vent.The four typical poly-meric nanocomposites were prepared by mild mixing method.The dispersion of nano-CaCO_(3) in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy(SEM).The molecular weights of polycarbonate(PC)and its nanocomposite showed that the degradation had not occurred during the mild mixing processing.The mechanical properties of the composite with 1.5 wt-% nano-CaCO_(3) improve slightly.It proved that this approach is suitable for the preparation of nano-composites based on both polar and non-polar polymers.展开更多
A new technique was proposed to enhance the adhesive strength of ultrahigh molecular weight polyethylene （UHMWPE） fibers. Polar polymer was implanted into UHMWE gel fibers during extracting process and can then be t...A new technique was proposed to enhance the adhesive strength of ultrahigh molecular weight polyethylene （UHMWPE） fibers. Polar polymer was implanted into UHMWE gel fibers during extracting process and can then be trapped on the surface of the fibers after subsequent ultra-drawing. The physical and chemical changes in the fiber structure were examined with scanning electron microscopy （SEM） and Fourier transform infrared （FTIR） spectroscopy. The mechanical and interfacial adhesion properties of UHMWPE fibers were investigated with tensile testing. The results showed that there were polar groups on the smface of pretreated UHMWPE fiber. The interracial shear strength of UHMWPE fibers with epoxy resin was greatly improved without sacrificing the excellent mechanical p^perties of fibers. After pretreated with ethylene/vinyl acetate copolymer （EVA）, the shear strength of the interface between fiber and epoxy resin increased from 1.06 to 2.49 MPa, while the integrated mechanical properties d the pretreated UHMWPE fibers were still optimal.展开更多
The globally increasing demands for polymer materials stimulate the significantly intense attention focused on the Lewis pair polymerization(LPP) of various polar vinyl monomers catalyzed by Lewis pairs(LPs) composed ...The globally increasing demands for polymer materials stimulate the significantly intense attention focused on the Lewis pair polymerization(LPP) of various polar vinyl monomers catalyzed by Lewis pairs(LPs) composed of Lewis acid(LA) and Lewis base(LB). According to the degree of interaction between LA and LB, LPs could be divided into classical Lewis adduct(CLA), interacting Lewis pair(ILP) and frustrated Lewis pair(FLP). Regulation of the Lewis basicity, Lewis acidity, and steric effects of these LPs has a significant impact on the polymer chain initiation, propagation and termination as well as chain transfer reaction during polymerization. Compared with other polymerization strategies, LPP has shown several unique advantages towards the polymerization of polar vinyl monomers such as high activity, control or livingness, mild conditions, and complete chemo-or regioselectivity. We will comprehensively review the recent advances achieved in the LPP of polar vinyl monomers according to the classification of the employed LPs based on different LAs, by highlighting the key polymerization results, polymerization mechanisms as well as the currently unmet challenges and the future research directions of LPP chemistry.展开更多
基金supported by the 973 Program (No.2014CB643503)National Natural Science Foundation of China (Nos.51373150,51461165301)Zhejiang Province Natural Science Foundation (No.LZ13E030002)
文摘The n-channel behavior has been occasionally reported in the organic field-effect transistors （OFETs） that usually exhibit p-channel transport only. Reconfirmation and further examination of these unusual device performances should deepen the understanding on the electron transport in organic semiconductors. 6,13-bis（triisopropyl-silylethynyl） pentacene （TIPS-pentacene）, a widely examined p-channel material as Au is used for source-drain electrodes, has recently been reported to exhibit electron transport when grown from non-polar solvent on divinyltetramethyldisiloxanebis （benzocy- clobutene） （BCB） dielectric, spurring the study on this unusual electron transport. This paper describes FET characteristics of solution-grown TlPS-pentacene single crystals on five polymer gate dielectrics including polystyrene （PS）, poly（methyl methacrylate） （PMMA）, poly（4-vinyl phenol） （PVP）, poly（vinyl alcohol） （PVA） and poly（vinylidene fluoride-trifluoroethylene-chlorofluoroethylene） （P（VDF-TrFE-CFE））. In addition to the p-channel behavior, electron transport occurs in the crystals on PMMA, PS, thick PVA （40 nm） and a bilayer dielectric of PMMA on P（VDF-TrFE-CFE）, while does not on PVP and thin PVA （2 nm）. The two distinct FET characteristics are consistent with the previous reported trap effect of hydroxyl groups （in PVP and PVA） and reduced injection barrier by Na~ ions （as impurity in PVA）. The highest electron mobility of 0.48 cm2 V-1 s-1 has been achieved in the crystals on PMMA. Furthermore, the electron transport is greatly attenuated after the crystals are exposed to the vapor of a variety of polar solvents and the attenuated electron transport partially recovers if the crystals are heated, indicating the adverse effect of polar impurities on electron transport. By reconfirming the n-channel behavior in the OFETs based on TIPS-pentacene, this work has implications for the design of n-channel and ambipolar OFETs.
基金The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China(Grant No.10590351)Sichuan University Youth Science Foundation(Grant No.06007).
文摘An novel compounding process using nano-CaCO_(3) aqueous suspension for preparing polymer/nano-CaCO_(3) composites with nanoparticles dispersed at the nanoscale is reported.The process is called the mild mixing method.In this method,the pre-dispersed nano-particle suspensions are blended with melting polymers in a weak shearing field using an extruder,followed by removing the water from the vent.The four typical poly-meric nanocomposites were prepared by mild mixing method.The dispersion of nano-CaCO_(3) in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy(SEM).The molecular weights of polycarbonate(PC)and its nanocomposite showed that the degradation had not occurred during the mild mixing processing.The mechanical properties of the composite with 1.5 wt-% nano-CaCO_(3) improve slightly.It proved that this approach is suitable for the preparation of nano-composites based on both polar and non-polar polymers.
文摘A new technique was proposed to enhance the adhesive strength of ultrahigh molecular weight polyethylene （UHMWPE） fibers. Polar polymer was implanted into UHMWE gel fibers during extracting process and can then be trapped on the surface of the fibers after subsequent ultra-drawing. The physical and chemical changes in the fiber structure were examined with scanning electron microscopy （SEM） and Fourier transform infrared （FTIR） spectroscopy. The mechanical and interfacial adhesion properties of UHMWPE fibers were investigated with tensile testing. The results showed that there were polar groups on the smface of pretreated UHMWPE fiber. The interracial shear strength of UHMWPE fibers with epoxy resin was greatly improved without sacrificing the excellent mechanical p^perties of fibers. After pretreated with ethylene/vinyl acetate copolymer （EVA）, the shear strength of the interface between fiber and epoxy resin increased from 1.06 to 2.49 MPa, while the integrated mechanical properties d the pretreated UHMWPE fibers were still optimal.
基金supported by the National Natural Science Foundation of China (21774042,21871107,and 21422401)
文摘The globally increasing demands for polymer materials stimulate the significantly intense attention focused on the Lewis pair polymerization(LPP) of various polar vinyl monomers catalyzed by Lewis pairs(LPs) composed of Lewis acid(LA) and Lewis base(LB). According to the degree of interaction between LA and LB, LPs could be divided into classical Lewis adduct(CLA), interacting Lewis pair(ILP) and frustrated Lewis pair(FLP). Regulation of the Lewis basicity, Lewis acidity, and steric effects of these LPs has a significant impact on the polymer chain initiation, propagation and termination as well as chain transfer reaction during polymerization. Compared with other polymerization strategies, LPP has shown several unique advantages towards the polymerization of polar vinyl monomers such as high activity, control or livingness, mild conditions, and complete chemo-or regioselectivity. We will comprehensively review the recent advances achieved in the LPP of polar vinyl monomers according to the classification of the employed LPs based on different LAs, by highlighting the key polymerization results, polymerization mechanisms as well as the currently unmet challenges and the future research directions of LPP chemistry.
