侧链含氨基的聚(对亚苯基亚乙炔基-对亚苯基-咔唑)三元共聚物的合成及其聚集态下荧光特性

通过Sonogashira偶联反应制备了含有4-2-(对苯胺)乙烯基]苯(M1)、2,5-二戊烷氧基-1,4-二乙炔基苯(M2)和9-辛基咔唑(M3)3种结构单元的三元共轭聚合物PPEC,并通过核磁共振氢谱确定了3种结构单元的比例为0.54∶1.00∶0.46(M1∶M2∶M3).由于在PPEC的侧链中含有氨基基团,通过在PPEC的THF溶液中分别加入水、甲醇和正己烷,诱导其产生聚集,其聚集后的荧光性质表现出明显的不同,在THF与水的混合溶剂中,PPEC发光强度会随着水含量的增加先是急剧降低,而后在高水含量时发光强度又显著增强;在THF与甲醇的混合溶剂中,PPEC发光强度随着甲醇的加入只是逐渐降低;在THF与正己烷的混合溶剂中,PPEC的发光强度则会随着正己烷的增加而增强.该结果表明氨基通过与水,或者自身所形成氢键作用,改变了PPEC分子链之间的聚集态结构,降低了分子内旋转非辐射能量效率,从而有效改善共轭聚合物的主链发光性质,这为设计聚集态下(或固态下)高性能的荧光共轭聚合物提供了一种新思路.

SYNTHESIS AND LUMINESCENT PROPERTIES OF POLY(PHENYLENEETHYNYLENE-CARBAZOLE)S WITH ANILINE AS SIDE-GROUPS

The poly(phenylene-ethynylene-carbazole)(PPEC) with 4-vinylaniline pendant groups was synthesized through Pd-catalyzed Sonogashira coupling polymerization between 4-2-(2,5-dibromophenyl)vinyl] aniline(M1),1,4-di-2,5-bis(pentyloxy)(M2) and 3,6-dibromo-9-octylcarbazole(M3).The ratio of aniline unit to ethynyl-benzene unit to carbazole unit at 0.54∶1∶0.46 was determined by1H NMR spectrum.When PPEC is aggregated by adding nonsolvents such as water,methanol and hexane into its THF solution,the fluorescence intensity and the maximum emission peak of PPEC changed drastically.The fluorescence intensity gradually decreased upon addition of water into PPEC THF solution before the ratio of THF to water arrived at 50∶50.The fluorescent intensity of PPEC increased in turn after water fraction is beyond 60% in the mixture of THF and water.When methanol was added into its THF solution,however,PPEC showed an aggregation-caused quenching(ACQ) characteristic.The emission of PPEC is only enhanced by aggregation when adding n-hexane into its THF solutions,exhibiting an aggregation-induced emission enhancement(AIEE) effect.The result indicates that amino groups can strengthen the inter-chain and intra-chain interactions in PPEC and restrict the non-radiative energy transition.This strategy thus provides a new concept for designing highly emissive conjugated polymers by adjusting side-group interaction.