Synthesis And Properties Of Branched Interrupted Conjugation Polymers By Friedel-Crafts Polymerization

Developing simple,efficient,convenient and atom-economical methods to synthesize optoelectronic functional polymer semiconductors with novel structures and desired performances is of great important for the development of theoretical research and industrial in the field of organic electronics.At the beginning of our studies,we proposed the design and synthesis of polymer semiconductors through Friedel-Crafts polymerization of fluorenyl tertiary alcohols.Kinds of branched interrupted conjugation polymers(BICPs)were prepared.Then,combine with the p-n energy band theory and Friedel-Crafts polymerization,p-n type BICPs were prepared.Through the Friedel-Crafts postfunctional polymerization,the end groups of BICPs were hindered functional with other groups.Tunable energy gaps of BICPs with stable spectral and electrochemical were obtained.At last,the optoelectronic properties of these polymers were systemically studied.These charge storage properties were studied by using these polymers in transistor memories as the polymer electret layers.On the other hand,graphene were growth on copper-nickel alloy nanofibers by chemical vapor deposition(CVD)and patterned reduced graphene oxide(rGO)conductive films were prepared through high temperature reduction method,respectively.After that,all-solution processable organic memory device was prepared by using patterned rGO as the top and bottom electrodes,hindered functionalized polymer as the active layers.The details of the dissertation are as follows: 1.The design and synthesis of polymer semiconductors were introduced briefly,especially the synthesis of organic semiconductor materials by the Friedel-Crafts reaction of fluorenyl tertiary alcohols and the three-dimensional branched conjugated polymers and their application in optoelectronic devices.Then,an overview of the research progress of polymer electrets in the organic field effect transistor memories and flexible organic memory devices were presented.Finally,the design ideas and main studies of this dissertation were put forward.2.Based on the research foundation of our group in the synthesis of organic semiconductor materials through BF3·Et2O catalyzed Friedel-Crafts reaction of fluorenyl tertiary alcohols,we proposed the Friedel-Crafts polymerization of ABx(x ? 2)tertiary alcohols for the synthesis of BICPs.The new polymerization method exhibits the characterization of simple,efficient,atom-economical,and non-metal catalyst.After careful study the polymerization conditions,it is found that the polymerization process was finished in a very short time(< 5 min).Polymers with molecular weight(Mn)of 22700 g/mol and narrow polydispersity index(PDI = 1.52)were obtained through slow monomer addition polymerization.After that,a novel series of fluorene and cyclopentadithiophene based BICPs were prepared and these optoelectronic properties were studied.The cyclopentadithiophene based BICPs exhibit near infrared absorption spectra.3.p-n type fluorenyl tertiary alcohols containing electron donating group,i.e.,carbazole or thiophene(p-type group)and electron-withdrawing group,i.e.,cyano(n-type group)were designed and synthesized according to the p-n energy band theory.p-n type BICPs were prepared through Friedel-Crafts polymerization.Spectral characterization revealed that the absorption and emission peaks exhibit red-shift in comparison with the BICPs which do not contain cyano groups.The emission peaks in thin film state indicated that the introduction of cyano groups not only suppress the green emission peaks but also reduces the bandgaps of these polymers,which is good for the carrier injection.4.The HICP,i.e.,PCz PF,with carbazole as the end functional groups was hindered functional with 9-phenyl-9H-fluorene(PF)or 9,9,9'',9''-tetraoctyl-9'-phenyl-9H,9'H,9''H-2,2':7',2''-terfluorene(TF)through BF3·Et2O catalyzed Friedel-Crafts postfunctional polymerization.We found that the introduction of functional groups improve the spectral and electrochemical stability.Impressively,postfunctional with PF groups increased the HOMO energy level and decreased the LUMO energy level,which regulate the energy gaps of the polymer effectively.5.In order to study the relationship between the functional groups and the charge storage properties of CIHPs.CIHPs,including PCzPPF,PCzPF,PCNCzPF and PCPDT8,were used as the polymer electret layers in transistor memories.The programming progress was conducted by applied a negative pulse on these transistor memories.Erasing process was realized by light irradiation these devices.Interestingly,all of these transistor memories exhibit stepwise negative shifts of transfer curves with the increase of the negative gate bias.In this case,PCPDT8 containing high electron density cyclopentadithiophene group and p-n type PCNCzPF based transistor memories,exhibited larger memory windows than others,which are 34.2 and 45.0 V,respectively.The positive shift of the transfer curve was occurred when a positive gate voltage was applied and combined with light irradiation,indicating the injection of electron into the electret.After applying a negative pulse,the transfer curves return to the initial state.In this case,PCzPPF and PCzPF based transistor memories exhibited large memory windows of 42.7 and 40.5 V,separately,which are higher than PCNCzPF and PCPDT8 based devices.Since these devices could be injected hole into the electret layer by applying negative pulse and electron by applying positive gate voltage combined with light irradiation,respectively,these devices exhibit ambipolar memory properties.In this case,the memory windows of these transistor memories are the accumulation of the memory windows from both the hole-trapping mode and the electron-trapping mode.As a result,the memory windows of these devices by using PCzPPF,PCzPF,PCNCzPF and PCPDT8 as the electret layer are 73.3,69.6,63.6 and 69.3 V,respectively.6.In order to prepare all-solution processable,flexible organic electronic devices by using these BICPs,we tried to prepare the flexible graphene electrodes.We first prepare the polymer nanofibers containing metal salt(copper or nickel acetate),following calcination and thermal reduction process to prepare metal nanofibers.By using these obtained metal nanofibers as the templates and polystyrene as the solid carbon source,graphene was grown on these nanofibers at low temperature through CVD method,the growth temperature is 450 oC.The graphene coated Cu–Ni NFs exhibited excellent anti-oxidation and anti-corrosion properties.After that,the flexible,green light emissive ACEL device has been demonstrated by using graphene coated Cu–Ni NF thin films as the electrode.On the other hand,patterned rGO conductive films were prepared through high temperature reduction method and were used as the top and bottom electrodes for all-solution processable organic memory device which with hindered functionalized polymer as the active layers.The device exhibited flash memory effect with ON/OFF ratio up to 3.0×103?The current in both of the ON and OFF states under the bending condition remained stable without any substantial current fluctuation,indicating good mechanical endurance of the organic memory device.It was believed that the idea of all-solution processable flexible organic memory device can also be used for the preparation of other organic devices.