Synthesis And Properties Of N-type Copolymers Based On Benzopyrrolidone

For n-type conjugated polymers,both low-lying the highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)energy levels(~ 4.0 eV)are necessary.The low-lying HOMO energy level could build larger barrier to block hole injection.Meanwhile,the low-lying LUMO energy level would facilitate electron injection and transport.Owing to the excellent conjugated degree,high coplanarity and strong electron-withdrawing ability,benzodipyrrolidone unit can effectively reduce the energy level of the polymers,and obtain high-performance n-type polymers.In this dissertation,a series of conjugated polymers were prepared by copolymerizing different benzopyrrolidinone derivative monomers with thiazole and nitrile-substitutedthiophene monomers through Stille coupling reaction.Their photophysical properties,electrochemical properties and thermal stability are characterized and discussed detailedly.1.The copolymerization of benzene substituted benzodipyrrolidone derivative and different thiazole derivatives.Two different thiazole derivatives(M and N)were Stille copolymerized with benzodipyrrolidone derivative to obtain copolymers PBDPP-M and PBDPP-N.The molecular weight,photophysics properties,electrochemical properties and thermal stability were discussed.In film state,the absorption range of the polymers PBDPP-M and PBDPP-N covers the visible light region and extends to the ultraviolet and infrared regions,the absorption peaks in longer wave band are 594 nm and 564 nm,respectively.The enhanced electron-withdrawing ability of the reaction unit results in the blue-shift of polymers.To a certain degree,the stronger electron-withdrawing ability,the eaier to obtain low HOMO / LUMO energy level.The HOMO energy levels of the polymers PBDPP-Mand PBDPP-N are-5.03 eV and-5.10 eV,and the LUMO energy levels are-3.63 eV and-3.75 eV,respectively.Both polymers have a low molecular frontier orbital energy level,conforming to the general energy level characteristics of n-type polymers.Both polymers have good thermal stability and the thermal decomposition temperature of polymers is 301 ℃ and 376 ℃,respectively.2.The random copolymerization of thiophene substituted benzodipyrrolidone derivative and different nitrile-substituted thiophene derivatives.By controlling the ratio of thiophene substituted benzodipyrrolidone(BDPT)monomer to nitrile-substituted thiophene monomer,two different nitrile-substituted thiophene(TCN and T2CN)were Stille copolymerized with benzodipyrrolidone derivative and thiophene to obtain PBDPT-TCN and PBDPT-T2 CN copolymers,respectively.In film state,with the same BDPT unit content,as the number of cyanogroup decreases,the TCN unit has a stronger electron-donating ability,which contributes to intramolecular charge transfer.Compared with PBDPT-T2 CN polymers,PBDPT-TCN polymers result in a red shift.The absorption peaks in longer wave band of PBDPT-TCN20,PBDPT-TCN10 and PBDPT-TCN5,which are synthesized by controlling the TCN content,are 827 nm,794 nm,and 756 nm,respectively.The absorption peaks in longer wave band of PBDPT-T2CN20,PBDPT-T2CN10 and PBDPT-T2CN5,which are synthesized by controlling the T2 CN content,are 798 nm,788 nm,and 783 nm,respectively.With the decrease of BDPT unit content,the polymers have little effect on the HOMO energy level,and the LUMO energy level gradually decreases.The HOMO energy level and LUMO energy level of the PBDPT-TCN polymers are-5.07 eV and-3.84 eV,respectively.And the PBDPT-T2 CN polymers are-5.10 eV and-3.86 eV,respectively,its molecular orbital energy level is in the typical energy level range of n-type polymers.All of polymers have good thermal stability and the thermal decomposition temperature of polymers is 249℃,270℃,325℃ and 292℃,319℃,374℃,respectively.