针对发光共轭聚合物稀溶液在干燥形成固体时的荧光淬灭问题, 通过高分子聚乙烯醇(PVA)的氢键网络调控水溶性共轭聚噻吩在溶液中的聚集行为和构象, 并采用不同的干燥方式实现了调控其固体光学性质的目的. 紫外-可见光吸收、荧光发射光谱测试表明, 在水溶液中PVA可以分散共轭聚合物链, 并增强其共平面性; 高温干燥后, 聚噻吩薄膜与无PVA添加的聚噻吩溶液的荧光性质相似; 而采用冷冻干燥法, 薄膜则保留了添加PVA后混合溶液的发光特性. 该结果表明, PVA对聚噻吩在溶液状态下的聚集/分子构象的调控行为随干燥方式的不同得到了不同程度的保留——高温加热干燥仅维持了PVA对聚噻吩的分散作用; 而冷冻干燥则完整保留了PVA与聚噻吩的分子间相互作用, 将溶液中分子的分散状态和构象同时固定. 本研究从干燥方式的角度为固态共轭聚合物聚集行为及发光性质的调控提供了新的策略.

Water-soluble conjugated polymers have attracted enormous attention because of their water solubility and attractive optical properties. However, they often suffer from low emission quantum yield due to their strong inter-chain interaction and concomitant exciton quenching, especially in the solid state. To enhance the emission of the water-soluble conjugated polymers, strategies of decreasing the aggregation tendency of the polymers and controlling the backbone conformations are often adopted. In this work, to solve the problem of aggregation-caused quenching of luminescent conjugated polymer dilute solution during drying, we regulate the aggregation behavior and backbone conformation of a water-soluble conjugated polythiophene (PMNT) with polyvinyl alcohol (PVA) by intermolecular interactions, e.g. hydrogen bonding, and obtained tunable emissive PMNT thin films. Specifically, when PMNT in solution state is blended with PVA, obvious red shift of absorption and emission maxima and higher fluorescence intensity are observed, indicating that PVA molecules isolate the PMNT chains, reduce the degree of chain flexibility and increase backbone rigidity. Furthermore, by varying dry methods, we obtained PMNT solid films of tunable light absorption/emission properties: the solid films fabricated through splat cooling and in-situ lyophilization preserve the optical properties of the mixed solution of PVA and PMNT; the films fabricated through heat drying exhibit the similar optical properties with those of PMNT solution without adding PVA. Moreover, the emission quantum yield of the solid film prepared by the lyophilization method was enhanced compared with that of the solid film prepared by heat drying. These results suggest that the aggregation/conformation regulations of PMNT solution by PVA are retained in different degrees dependent on the drying methods: heat drying only maintains the isolation effect of PVA on PMNT; lyophilization readily preserve the interactions between PVA and PMNT, locking their disperse states and conformations. This study provides a strategy for regulating the aggregation behaviors and optical properties of solid conjugated polymers from the perspective of drying method.