Synthesis and Photo Electronic Properties of Novel π-Stacked Polymers

我们发现，在适当的条件下，自由基聚合可以得到具有π堆积构象的聚二苯富烯，也可以得到阴离子聚合。自由基聚合产物中含有少量的缺陷构象。这种局部构象缺陷有助于提高聚合物的溶解度。另外，合成了一种新型的大体积二苯并富烯衍生物--2，7-二叔丁基二苯并富烯，考察了侧链对单体聚合性能和聚合产物性能的影响。这种体积较大的新单体在阴离子聚合中表现出相对较低的反应活性，导致齐聚物主要是三聚体。所得低聚物的光物理性质揭示了未取代的聚二苯并富烯在吸收光谱中表现出的低色特性和在荧光光谱中表现出的准分子发射。此外，还测量了齐聚二苯并富烯的化学氧化生成的自由基阳离子物种的吸收光谱，以获得有关电荷输运性质的信息。自由基阳离子物种在近红外区有一个明显的电荷转移带，支持电荷通过堆积荧环的传输。在上述研究的基础上，采用立体定向阴离子聚合技术合成了具有不同规整度的聚二苯基富烯聚甲基丙烯酸酯，并对聚合物的结构和性能进行了表征。这项研究的目的是寻找一种新的具有聚甲基丙烯酸甲酯主链的π堆叠聚合物。虽然聚合物在溶液中不具有稳定的π堆积构象，但它们的光物理性质取决于主链的规整性。

We found that free-radical polymerization under appropriate conditions can give polydibenzofulvene having a π-stacked conformation as well as anionic polymerization. The free-radical polymerization product contained a small amount of defective conformation incorporated in the chain. Such a partial conformational defect was revealed to contribute to increase solubility of the polymer. In addition, as a new bulky dibenzofulvene derivative, 2,7-di-t-butyldibenzofulvene, was synthesized and polymerized in order to examine the effect of the side chain on polymerizability of the monomer and properties of the polymerization product. The bulky new monomer showed relatively low reactivity in anionic polymerization and led to oligomers mainly up to trimer. Photophysical properties of the obtained oligomers shed light on how unsubstituted polydibenzofulvene shows hypochromicity in absorption spectra and excimer emission in fluorescence spectra. Furthermore, absorption spectra of a radical cation species of oligo- and polydibenzofulvene generated by their chemical oxidation were measured in order to obtain information on charge transport properties. The radical cation species indicated a clear charge transfer band in near IR region, supporting the proposed charge transport through the stacked fluorene rings. In addition to the above investigations on polydibenzofulvene, poly(9-fluorenyl methacrylate) having various tacticity was synthesized by stereospecific anionic polymerization technique and the structure and the properties of the polymers were examined. The aim of this investigation was to find a new π-stacked polymer having a polymethacrylate backbone. Although the polymers were found not to have a stable π-stacked conformation in solution, they showed different photophysical properties depending on the main-chain tacticity.