Synthesis of terpolymers consisting of two electron-donating monomers, viz. styrene and vinyl acetate with one electron-accepting monomer, i.e. acrylonitrile, initiated by p-nitrobenzyl triphenyl phosphonim ylide in d...Synthesis of terpolymers consisting of two electron-donating monomers, viz. styrene and vinyl acetate with one electron-accepting monomer, i.e. acrylonitrile, initiated by p-nitrobenzyl triphenyl phosphonim ylide in dioxane as diluent at 65°C for 150 min has been studied. The kinetic expression is Rpα[I]0.8[Sty] 1.2[VA] 1.4 [AN]1.2. The terpolymer composition was determined by the Kelen-Tüdos method. The values of reactivity ratios using r1 (Sty + VA) = 0.1 and r2 (AN) = 0.005. The overall activation energy is 46 kJ●mol●L–1. The formation of terpolymer is confirmed by the FTIR spectra showing bands at 3030 cm–1, 1598 cm–1, and 2362 cm–1, confirming the presence of phenyl, acetoxy and nitrile group respectively. The terpolymer has been characterized by 1H-Nuclear Magnetic Resonance, 13C-Nuclear Magnetic Resonance. The Differential Scanning Calorimetric curve shows the Tg of the polymer as 149.5°C. A scanning electron microscope confirms the polymer to be phosphorus free. Electron.Spin.Resonance spectra confirms phenyl radical responsible for initiation.展开更多
Through the modulation of the dipolar entropy under an applied electric field(E),a reversible temperature change(ΔT)could be achieved in a dielectric material,which is known as the electrocaloric(EC)effect.Among all ...Through the modulation of the dipolar entropy under an applied electric field(E),a reversible temperature change(ΔT)could be achieved in a dielectric material,which is known as the electrocaloric(EC)effect.Among all EC materials,ferroelectric terpolymer P(VDF-TrFE-CFE)has been regarded as one of the most promising EC materials owing to its large EC effect and superior thermal stability.Yet,the low EC strength limits the application of terpolymers in realistic cooling devices.In this work,using the thermal treatment of quenching and low-temperature annealing,the terpolymers with significantly decreased crystalline size are prepared with their EC performances investigated.Compared to the normal ones,the terpolymers with smaller crystalline size exhibit substantially enhanced EC strength.The better EC performance may be mainly attributed to the lower energy barriers for dipole orientation,which gives rise to higher polarization at low electric fields.This work emphasizes the critical role of crystalline size on the macroscopic properties of EC polymers.展开更多
Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)P(VDF-TrFE-CFE)is a relaxor ferroelectric polymer,which exhibits a temperature-independent electrocaloric effect at room temperature.In this work,the ele...Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)P(VDF-TrFE-CFE)is a relaxor ferroelectric polymer,which exhibits a temperature-independent electrocaloric effect at room temperature.In this work,the electrocaloric effect in P(VDF-TrFE-CFE)film was directly analysed using infrared imaging.P(VDF-TrFE-CFE)64.8%/27.4%/7.8%(in mole)film of(15±1)mm thickness was deposited on polyethylene naphthalate substrate.Direct ECE of P(VDF-TrFE-CFE)film was measured from 15 to 35C at different electric fields.A maximum adiabatic temperature change(DTad)of 3.58 K was measured during the cooling cycle at a field of 100 V/mm at 30C.Finite element analysis of temperature dissipation through the sample estimated that the actual temperature change within P(VDF-TrFE-CFE)film was 4.3 K.Despite the thermal mass of the substrate,a substantial ECE was observed in P(VDF-TrFE-CFE)films.This electrocaloric terpolymer composition could be of interest for electrocaloric cooling applications.展开更多
文摘Synthesis of terpolymers consisting of two electron-donating monomers, viz. styrene and vinyl acetate with one electron-accepting monomer, i.e. acrylonitrile, initiated by p-nitrobenzyl triphenyl phosphonim ylide in dioxane as diluent at 65°C for 150 min has been studied. The kinetic expression is Rpα[I]0.8[Sty] 1.2[VA] 1.4 [AN]1.2. The terpolymer composition was determined by the Kelen-Tüdos method. The values of reactivity ratios using r1 (Sty + VA) = 0.1 and r2 (AN) = 0.005. The overall activation energy is 46 kJ●mol●L–1. The formation of terpolymer is confirmed by the FTIR spectra showing bands at 3030 cm–1, 1598 cm–1, and 2362 cm–1, confirming the presence of phenyl, acetoxy and nitrile group respectively. The terpolymer has been characterized by 1H-Nuclear Magnetic Resonance, 13C-Nuclear Magnetic Resonance. The Differential Scanning Calorimetric curve shows the Tg of the polymer as 149.5°C. A scanning electron microscope confirms the polymer to be phosphorus free. Electron.Spin.Resonance spectra confirms phenyl radical responsible for initiation.
基金supported by Basic Science Centre Program of NSFC(Grant No.51788104)the NSF of China(Grant No.51625202,and 51572141)+1 种基金the National Key Research and Development Program(Grant No.2017YFB0701603)the National Basic Research Program of China(Grant No.2015CB654603).
文摘Through the modulation of the dipolar entropy under an applied electric field(E),a reversible temperature change(ΔT)could be achieved in a dielectric material,which is known as the electrocaloric(EC)effect.Among all EC materials,ferroelectric terpolymer P(VDF-TrFE-CFE)has been regarded as one of the most promising EC materials owing to its large EC effect and superior thermal stability.Yet,the low EC strength limits the application of terpolymers in realistic cooling devices.In this work,using the thermal treatment of quenching and low-temperature annealing,the terpolymers with significantly decreased crystalline size are prepared with their EC performances investigated.Compared to the normal ones,the terpolymers with smaller crystalline size exhibit substantially enhanced EC strength.The better EC performance may be mainly attributed to the lower energy barriers for dipole orientation,which gives rise to higher polarization at low electric fields.This work emphasizes the critical role of crystalline size on the macroscopic properties of EC polymers.
基金Fonds National de la Recherche(FNR)of Luxembourg under the grant THERMODIMAT/C20/MS/14718071//Defay,CAMELHEAT/C17/MS/11703691/Defay,MASSENA PRIDE/MASSENA/15/10935404/Defay Siebentritt and CALPOL BRIDGES 2O2O/MS/15410586/Defay.
文摘Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)P(VDF-TrFE-CFE)is a relaxor ferroelectric polymer,which exhibits a temperature-independent electrocaloric effect at room temperature.In this work,the electrocaloric effect in P(VDF-TrFE-CFE)film was directly analysed using infrared imaging.P(VDF-TrFE-CFE)64.8%/27.4%/7.8%(in mole)film of(15±1)mm thickness was deposited on polyethylene naphthalate substrate.Direct ECE of P(VDF-TrFE-CFE)film was measured from 15 to 35C at different electric fields.A maximum adiabatic temperature change(DTad)of 3.58 K was measured during the cooling cycle at a field of 100 V/mm at 30C.Finite element analysis of temperature dissipation through the sample estimated that the actual temperature change within P(VDF-TrFE-CFE)film was 4.3 K.Despite the thermal mass of the substrate,a substantial ECE was observed in P(VDF-TrFE-CFE)films.This electrocaloric terpolymer composition could be of interest for electrocaloric cooling applications.
