Application Of Fluorene-based Conjugated Polymers Containing Nitrogen And Sulfur Heteroatomic For The Separation And Functionalization Of Semiconducting Carbon Nanotubes

In recent years,single-walled carbon nanotubes(SWCNTs)have attracted close attention due to their unique structure and electronic properties.However,SWCNTs obtained using conventional growth methods contain an amorphous a mixture of metals(m-)and semiconductors(sc-)as well as carbon and a small amount of catalyst.A large number of studies have shown that semiconducting carbon nanotubes(sc-SWCNTs)may be expected to become a substitute for the next generation of traditional semiconductors of silicon.Therefore,the effective separation of semiconductor-based SWCNTs greatly affects its application potential in the electronic field.Conjugated polymer(CPs)coating method separates semiconducting single-walled carbon nanotubes(sc-SWCNTs)has become a potential method for separating sc-SWCNTs due to its high separation yield,low cost and simple operation.At present,the separation of sc-SWCNTs by CPs coating method is mostly carried out in non-polar organic solvents such as toluene(TL)or tetrahydrofuran(THF),which are more harmful to human skin and respiratory tract.Some studies have shown that introducing functionalized characteristic groups into the side chains of conjugated polymers can functionalize the sorted polymer@carbon nanotube composite(CPs@SWCNTs)and dissolve it in environmentally friendly heavy water(D₂O).However,this method uses functionalized azide polymer,which has the risk of explosion and is not conducive to wide-scale promotion.In addition,most of the conjugated polymers that can sort sc-SWCNTs tend to inhibit the performance of sc-SWCNTs in field effect transistors(FETs)due to the schottky barrier at the electrode interface and poor conductivity.Although some studies have used trifluoroacetic acid(TFA)to remove the polymer coated on the wall of sc-SWCNTs,the"naked"sc-SWCNTs are released.However,this method is time-consuming and laborious,and a large amount of carbon nanotubes will be lost during multiple washing processes.To solve the above problems,this paper adopts the suzuki coupling reaction to synthesize a series of fluorene-based conjugated polymers that can select sc-SWCNTs.The CPs@SWCNTs complex soluble in methanol is successfully prepared with the functionalization of the copolymer side chain.And based on the excellent chemical properties and good coplanarity of thiophene,a stable high-carrier mobility field-effect transistor device is prepared.The specific research content are as follows:(1)A series of fluorene 9,9-bis[3-(N,N-dimethylamino)propylfluorene-co-2-methylpyrimidine polymer(FOA-Py)are synthesized.2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene(FO)as the first copolymerization unit,2,7-dibromo-9,9-bis[3-(N,N-dimethylamino)propyl]fluorene(FOA)as the second copolymerization unit and 2-methyl-4,6-dichloropyrimidine(Py)as the third copolymerization unit.¹H NMR and FT-IR are used to characterize the polymers.It is concluded that when the second copolymerization unit and the third copolymerization unit in the copolymer are both 50%(FOA-Py50),sc-SWCNTs with a purity greater than 95%can be sorted.With the aid of the side chain of the second copolymer unit 9,9-bis[3-(N,N-dimethylamino)propyl]can be quaternized,the FOA-Py50@SWCNTs dispersed in toluene is functionalized into FOA-Py50-Br@SWCNTs complex dissolved in methanol.This greatly reduces the harm caused by the toluene solvent.And study the theory that electron-rich polymer structure are more conducive to the selection of sc-SWCNTs by DFT calculation.(2)2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-9,9-dioctylfluorene as the first copolymerization unit,2,5-dibromo-3-methine(4-butoxyaniline)thiophene(BT)as the second copolymerization unit and 4,6-dibromopyrimidine(Py)as the third copolymerization unit to synthesize a series of fluorene-based donator-acceptor(D-A)with electron polymer of 3-methine(4-butoxyaniline)thiophene-co-pyrimidine.The polymers are characterized using¹H NMR,¹³C NMR,FT-IR,TG and GPC.When the second copolymerization unit and the third copolymerization unit of the copolymer are both 50%(FOBT-Py50),sc-SWCNTs with a purity greater than 95%can be selected.A field effect transistor with a carrier mobility of 1.06±0.86 cm²V^-1s^-1is fabricated using FOBT-Py50@SWCNTs.Based on the feature that the side chain-CH=N-of the second copolymerization unit can be cleavable and the pyrimidine ring of the third copolymerization unit can be protonated,the sc-SWCNTs in the FOBT-Py50@SWCNTs composite are completely released to obtain a field effect transistor with a carrier mobility of 0.83±0.44 cm²V^-1s^-1.(3)2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-9,9-dioctylfluorene as the first copolymerization unit,respectively use N,N'-bis-(5-bromo-thiophen-2-ylmethylene)-benzene-1,4-diamine and(4-iodo-phenyl)-[4-[2-(4-iodine-phenyl)-vinyl]-benzylidene]-diamine is used as the second type of copolymerization unit to synthesize fluorene containing bisthiophene(FO-N-TA)and biphenyl ring(FO-N-PA)schiff-based copolymer.The polymers are characterized using¹H NMR,¹³C NMR,FT-IR,TG and GPC.Both of these polymers can select sc-SWCNTs with a purity greater than 99%.The FO-N-TA@SWCNTs complex containing bisthiophene is applied to the channel material for transistors,and the stable field-effect transistor with carrier mobility of 16.48±7.41 cm²V^-1s^-1,on/off ratio of 1.05×10²is prepared.The carrier mobility of the device obtained with FO-N-TA@SWCNTs complex is 0.12±0.06 cm²V^-1s^-1,and the on/off ratio is 4.5×10¹The released SWCNTs are used to fabricate transistors(?=0.3±0.14 cm²V^-1s^-1),which were compared with the transistors fabricated by the FO-N-TA@SWCNTs complex.This further leads to the conclusion that the FO-N-TA polymer containing bisthiophene can improve the performance of semiconductor devices.