共轭高分子材料荧光颜色的调节机理及方法

Fluorescent Color Tuning of Conjugated Polymer Materials: Mechanisms and Methods

近年来,共轭高分子作为荧光材料的研究受到越来越多的关注。共轭高分子相对于小分子发光材料在材料加工和发光性能上均具有极大的优势,从而在生物成像、传感、编码和光电材料等方面均有良好的应用前景,而其发光颜色的调节在某些应用中是极为重要的。本文首先对共轭高分子荧光颜色调节的两大类机理进行了阐述:直接调节共轭聚合物发光体系的能隙以改变发光颜色,或者将具有不同荧光颜色的材料发出的光叠加获得新的表观颜色。我们还对具体的调节手段进行了初步分类,包括物理共混法、共聚法、改变聚合物主链或侧基结构,以及改变共轭高分子聚集态等方法;在列举具体调节手段同时还引入了共轭高分子体系的实例说明,并对其中调节荧光颜色的可能机理进行了探讨。

Conjugated polymers have received ever-increasing attention as fluorescent materials. They have many advantages compared w ith small-molecular fluorescent materials. As materials,conjugated polymers can be fabricated into different forms,such as thin films by spinning coating or drop casting,nano-/ micro- fibers by electrospinning,nano-/ micro- spheres,and micelle / vesicle / microtubule / nanoparticles by self-assembly. The great flexibility of conjugated polymers in processing makes it possible for them to meet the demands of different applications. With regard to the photophysics,the broader absorption allow s conjugated polymers to be excited by different light sources. In addition,the high resistance to the photobleaching,or photostability,guarantees a long lifetime when conjugated polymers in real applications. These advantages allow conjugated polymers to be used in different fields,ranging from fluorescent bioimaging and sensors,to optical encoding and photoelectric displays. Some applications,such as encoding and display,require that the fluorescent materials have various emission colors. Thus fluorescent color tuning is very important and also very challenging for realization of these applications. This article gives some detailed discussion about the main mechanisms for the color tuning,basedon the adjustment of the band gap of the single emission specie,or based on the chromaticity diagram advanced by International Commission on Illumination（ CIE） for blending different emission species. The different methods for the color tuning are also discussed, such as physical blending of several emission species,copolymerization of different monomers,varying the substituent or the backbone of conjugated polymers,and changing the state of aggregation. Detailed examples with different chemical structures of polymers are provided to make clear illustrations about these mechanisms / methods.