聚芴单链构象及凝聚态结构的液-固跨相传递过程研究

Polyfluorene is a kind of classical conjugated polymer with excellent blue light emitting property. At present, its application is generally in the form of photoelectric thin film devices, and the precursor solution needs to be processed by spin coating, spraying or inkjet printing. There is a close relationship between the chain stacking mode and the photoelectric performance of the device. The chain conformation and condensed structure in the precursor solution may affect the surface shape of the device even the internal structure after the film formation, thus affecting the performance of the device. However, due to the existence of factors such as solvent volatilization, the chain condensed structure tends to change due to self-assembly behaviors during the transfer process from solution to film, thus affecting the photoelectric properties of the film. Based on the common conditions such as temperature, concentration, molecular weight and shear force, we plan to study the transfer factors and the changing mechanism of the single-strand conformation and condensed structure of the representative polyfluorene PFO molecules from the liquid phase solution to the solid phase film. At the same time, In-depth study of the relationship between chain structure changes, external field stimulation conditions and film ordering would be carried to build relevant models, finally controlling the order degree of the aggregate structure in the precursor solution to introduce it into the film and improve the device photoelectric performance. This has important scientific significance for comprehensively understanding the dynamic evolution process of polymer chain condensed structure and further optimizing the performance of thin film devices.

聚芴是一类具有优良蓝光性能的共轭高分子，目前其应用一般是以光电薄膜器件的方式，需要将前体溶液以旋涂，喷涂或喷墨打印等方式进行处理。器件中链堆积方式与光电性能之间存在较为紧密的联系，前体溶液中的链构象及凝聚态结构会影响到成膜后器件的表面形状以乃至内部结构，从而影响到器件的性能。但由于溶剂挥发作用等因素的存在，链结构从溶液到薄膜的传递过程中往往会因自组装而发生变化，从而影响到薄膜的光电性能。本项目拟从温度、浓度、分子量和剪切力等常见条件出发，重点研究从液相溶液到固相薄膜这一跨相过程中，代表性聚芴PFO单链构象、凝聚态结构的传递影响因素及变化机理，深入探讨溶液中链结构变化、外场刺激条件与薄膜有序性之间的关系并建立相关模型，以期实现在前体溶液中调控聚集态结构的有序程度，将其完整引入薄膜，提高器件光电性能的目的。这对于全面理解高分子链凝聚态结构的动力学演变过程，进一步优化薄膜器件性能有重要意义。

聚芴是一类具有优良蓝光性能的共轭高分子，其前体溶液中的链构象及凝聚态结构会直接影响到成膜后器件的表面形状、内部结构甚至器件性能。本项目从温度、浓度、分子量、剪切力等常见条件出发，重点研究了从液相溶液到固相薄膜跨相过程中，聚芴单链构象、凝聚态有序性结构的传递影响因素及变化机理并建立了相关模型。. 在本项目支持下，发表SCI论文4篇，顺利达成了溶液-薄膜过程的相关研究目标，并为下一步深化研究奠定了基础。其中重要结果与关键数据如下：. （1）系统深入地研究了分子量和溶剂对代表性聚芴PFO前体溶液中有序β构象和链凝聚态结构的影响。发现在良/劣溶剂混合过程中，构象的形成与链长有直接关系；且溶剂混合的加入顺序也会对有序性构象含量和凝聚态结构造成巨大影响。该部分工作发表在杂志Polymer上。. （2）研究了滴膜条件下，分子量及溶剂对PFO溶液中链凝聚态结构、β构象从溶液到薄膜传递过程的影响并提出溶液-薄膜链结构传递的三阶段理论：链结构从溶液-薄膜传递过程中有分子链聚集、聚集沉积和分子链折叠自组装三个过程，其中薄膜中的β构象主要是第三过程形成的。低分子量时单链难以自我折叠，且刚性较强。随着分子量增加，单链柔性增强，自我折叠能力增强，在溶剂挥发过程中自我折叠形成较多β构象。但若分子量过高，柔性过强，链与链之间的缠绕交联则会阻碍了分子链的自我折叠以及β构象的形成。该部分工作发表在杂志Phys. Chem. Chem. Phys上。. （3）研究了一种与聚芴PFO结构极为相似，且同样能形成较高β构象含量的聚芴高分子P7DPF。结果发现：良溶剂中，P7DPF链聚集体可以溶解成单链（α构象）；但在劣溶剂中β构象能够稳定存在于尺寸约为100 nm聚集体中，即使在高温（343K）加热和强力超声振荡后也不溶解。在向劣溶剂中加入良溶剂过程中，β构象的含量逐渐降低，聚集体中链堆砌密度及有序性也随之下降。基于以上现象，我们提出了有序聚集的溶解分步机制：先是有序性构象的转变，然后才是聚集体中的单链分散。相关工作发表在杂志Macromolecules上。