受体强度及D/A比对D-A型共轭聚合物几何结构和电子性质的影响研究  

The Effects of Acceptor Moiety and Donor-to-Acceptor Ratio on the Geometries and Electronic Properties of Thieno [3,2-b]thiophene-based Donor-Acceptor Alternating Copolymers

作　　者：陈明君[1] 傅杨武[1] 祁俊生[1] 

机构地区：[1]重庆三峡学院环境与化学工程学院,重庆404100

出　　处：《高分子学报》2016年第1期31-39,共9页Acta Polymerica Sinica

基　　金：重庆市教委科学技术研究项目(项目号KJ131102);国家自然科学基金(基金号21073144)资助

摘　　要：以Thieno[3,2-b]thiophene(TT)为电子供体(D),Benzo[c][1,2,5]thiadiazole(BT)、[1,2,5]thiadiazolo[3,4-g]quinoxaline(Td Q)、和Benzobis[1,2,5]thiadiazole(BBT)为电子受体(A),设计了供体-受体摩尔比(D/A比)分别为1∶1和2∶1的6种供体-受体交替排列的D-A型共轭聚合物.采用杂化的密度泛函方法(B3LYP),在6-31G(d)理论水平下研究了其几何结构和电子性质.研究发现,电子受体接受电子的能力和D/A比对基于TT的D-A型共轭聚合物的几何结构和电子性质有重要影响.对于D/A比相同的聚合物,电子受体接受电子的能力增强,聚合链上桥键的键长缩短,供体环上的碳碳双键的平均键长(L_(AD))增大而碳碳单键平均键长(L_(AS))减小.对由相同电子供体和受体构成的聚合物,D/A比增加,桥键变长.电子受体对D/A比为2∶1的聚合物的性质影响有显明的规律.当电子受体接受电子的能力增强,聚合物的能隙(Eg)变窄、价带(W_(VB))和导带(W_(CB))变宽、载流子有效质量(m_H和m_L)减小.研究发现,p-TdQ-TT和p-BBT-DTT能隙窄,能带相对较宽、载流子有效质量小,可能是的潜在的本征导电聚合物材料.Six types of donor-acceptor conjugated polymers were designed by choosing thieno [3,2-b]thiophene（ TT） as the electron donor and Benzo[c][1,2,5]thiadiazole（ BT）,[1,2,5]thiadiazolo[3,4-g]quinoxaline（ Td Q） or benzobis[1,2,5]thiadiazole（ BBT） as the electron acceptor unit. B3 LYP method is employed to investigate the electronic structure and properties of the designed TT-based donor-acceptor alternating copolymers. It is found that the electron-withdrawing ability of the acceptor and the ratio of donor to acceptor units（ D / A ratio） play a very important role in the geometries and electronic properties for the donoracceptor alternating copolymers. The bridge bond length and the average bond length of carbon-carbon single bond（ L_（AS）） in the donor unit decreases with an increase in the electron-withdrawing ability of the acceptor moiety. However,the average bond length of carbon-carbon double bond（ L_（AD）） in the donor unit shows a same trend as that of the acceptor strength. In addition,the bridge bond length increases with an increase in the D / A ratio for the copolymers. It is of interest to note that the electronic properties of the TT-based copolymers,especially for the copolymers with the D / A ratio of 2 ∶ 1,also exhibit a systematic trend with the acceptor strength. The band gap（ Eg） and effective mass of carriers（ both hole and electron,mHand mL） decrease,the bandwidth（ both valence and conduction band,WVB and WCB） increases systematically with an increase in the electron-withdrawing ability of the acceptor moiety. The theoretical results also suggest that p-Td Q-TT and pBBT-DT could have potential applications as an electrically conductive material due to their narrow band gap（ 0. 5 e V）,large bandwidth and small effective mass of holes and electrons.

关 键 词：噻吩并[3 2-b]噻吩 接受电子能力 D/A比 电子性质 

分 类 号：O631.11[理学—高分子化学]