由芴炔撑和苯并噻二唑组成的新型共轭聚合物的合成与光学性能

采用Pd(PPh₃)₄和CuI作为催化剂,在三乙胺和甲苯溶液中,采用2,7-二乙炔基-9,9-二辛基芴(PFE)和4,7-二溴-2,1,3-苯并噻二唑(BT),以不同配料比合成了一系列新型的聚芳炔聚合物。所有这些聚合物的数均分子质量M_n约为4000~12000,并在三氯甲烷和甲苯中都有很好的溶解性。研究了其紫外-可见吸收光谱、光致发光性能。随着共聚物中BT的增加,共聚物的光致发光的发射波长有少量红移,证明了由宽能带的2,7-二乙炔基-9,9-二辛基芴(PFE)和窄能带的4,7-二溴-2,1,3-苯并噻二唑(BT)组成的共聚物,由于激子在窄能带单元中的限制使得在宽能带单元和窄能带单元之间发生了有效的分子内的能量转移。因此在聚芴炔链中引入不同含量的窄带隙杂环单元可实现对聚芴发光颜色的调节。

Synthesis and Optical Properties of Novel Conjugated Copolymers Derived from Fluoreneethynylene and Benzothiadiazole

Poly(aryleneethynylene)s(PAEs) can be used in polymer light-emitting devices (PLED) and photovoltaic cells due to their relatively high efficient energy transfer and luminescence. The emission color of PAEs can be turned by incorporating narrow band-gap comonomers into the PAEs' backbone. A new class of poly(aryleneethynylene)s containing an aryl heterocyclic structure was prepared by Pd-catalyzed cross couplings between 4,7-dibromo-2,1,3-benzothiadiazole(BT)and 2,7-diet-hynylene-9,9-dioctylfluorene(PFE)with different feed radio of PFE to BT, using Pd(PPh₃)₄ and CuI as catalysts in the presence of triethylamine and toluene. In the case of Pd-catalyzed cross couplings, each individual narrow-band-gap unit is separated from both sides by wide-band-gap segments when the narrow-band-gap component is under or equal to 50% in the copolymer. The narrow-band-gap units function as exciton traps allow efficient intramolecular energy transfer from wide-band-gap segments to narrow-band-gap unit. All these polymers had a number-average (molecular) mass, M_n, about 4 000¹2 000 and showed good solubility in chloroform and toluene. The actual molar ratios of PFE to BT in the copolymers were estimated by means of elemental analysis. The results indicate that the actual ratio of PEF to BT in the copolymer is very close to the feed ratio. The absorption and photoluminescent spectra of the copolymers were studied. The maximal emissions of PL and UV spectra slightly red-shifted with gradual increase of BT's content. The result indicates that when the polymer contains alternating narrow band-gap aromatic units BT and large band-gap units PFE the tendency is to form a π-stacked structure which will be enhanced due to intermolecular charge transfer (CT) between polymer molecules. So that we could tune the emission color of polymers through attaching different ratio of narrow band-gap comonomer.