摘要
聚二乙炔(polydiacetylenes)具有平面的全共轭主链,并可被制备成宏观大小的单晶,因而是研究聚合物物理、化学性质的理想模型.它的物理、化学性质,特别是作为导电材料的导电机理与其价带及导带的结构密切相关.通过改变聚二乙炔的侧基可以对其主链几何结构及电子能带结构产生影响,进而改变其物理化学性质.
The influences of the side phenyls (PHs) on the electronic energy band-struc- ture of polydiaeetylenes have been studied by quantum-chemical EHCO-ASED method.When the backbone are changed from polybutatriene(PBT)to polydiacetylene(PDA),the band widths △E_(HO) and △E_(LU) decrease montonically from those of PBT to PDA,but the energy gap decreases from Eg(PBT)=0.43 eV to the minimum Eg(MIN)=0.11 eV firstly,and then increases to Eg(PDA)=1.43 eV(Table 2).Correspondingto the minimum,there is a symmetry inversion for HOCO and LUCO(Table 3).When PHs are coplanar with the backbone(PBT-PH1 and PDA-PH1),they willtake part in the conjugation of the system to a certain extent(Table 5),and cause:(Ⅰ)energy gaps Eg(PBT-PH1)and Eg(PDA-PH1)to change to 56% of Eg(PBT)and 76% of Eg(PDA)respectively(Table 4);(Ⅱ)the band widths,both △E_(HO)and △E_(LU) for PBT-PH1 and PDA-PH1,to decrease to 40—50% of those of PBTand PDA respectively(Table 4).When PHs are perpendicular to the plane of thebackbone(PBT-PH2 and PDA-PH2),the influences of PHs on the band structureare limitted(Table 4).According to the results and the discussions in this paper,it is shown that the intrinsic semiconductor characteristic of polydiacetylenes is hardto be improved obviously by the side group.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
1993年第2期256-262,共7页
Acta Physico-Chimica Sinica
基金
国家自然科学基金
关键词
聚二乙炔
电子能带结构
Polydiacetylenes
Structure of electronic energy bands
Organic semiconductor
EHCO-ASED
