手性取代聚(对亚苯基亚乙炔基-alt-间亚苯基亚乙炔基)的设计合成及其手性光性能研究

DESIGNED SYNTHESIS AND CHIROPTICAL PROPERTIES OF REGIOREGULAR POLY(p-PHENYLENEETHYNYLENE-alt-m-PHENYLENEETHYNYLENE) BEARING(-)-trans-MYRTANOXYL SIDE GROUPS

设计合成了两种主链结构相同、但取代方式不同的带有(-)-trans-桃金娘烷氧基手性侧基的规整连接聚(对亚苯基亚乙炔基-altr-间亚苯基亚乙炔基)(Myr-PMPE-1和Myr-PMPE-2),其中Myr-PMPE-1分子中手性取代基在分子链上均匀分布,而Myr-PMPE-2分子中手性取代基的分布则交替地存在局部"拥挤"和局部"松散".利用紫外-可见吸收光谱、荧光光谱和圆二色谱对两种聚合物膜的手性光性能进行了研究.结果表明,退火处理对Myr-PMPE-1膜的UV吸收和荧光光谱以及光学活性的影响都不明显,其最大不对称因子|gmax|为1.62×10-4;而退火处理对Myr-PMPE-2膜影响显著,未经退火处理或退火温度≤100℃时,Myr-PMPE-2膜几乎不显示光学活性,但当退火温度高于120℃时,随着退火温度的升高和退火时间的延长,Myr-PMPE-2膜的UV吸收和荧光光谱均稍有红移,特别是膜的光学活性显著提高,经140℃退火处理4 h后,其|gmax|可达3.07×10-3,比Myr-PMPE-1膜的高出1个数量级.

Two regioregular poly（p-phenyleneethynylene-alt-m-phenyleneethynylene） s beating （-）- trans-myrtanoxyl side groups with different substitution patterns were designed and synthesized, e. g. Myr-PMPE-1 and Myr-PMPE-2. In order to obtain regioregular polymer, a novel AB type monomer 1-（（5-bromo-2-myrtanoxyphenyl） ethynyl ）-4-ethynyl-2,5-myrtanoxybenzene and a novel AA type monomer 2,2＇- （2,5-dimyrtanoxy- 1,4-phenylene） bis （ethyne-2,1-diyl） bis （4-bromo-l-myrtanoxybenzene） were designed and synthesized by the strategy based on the different activity between bromo- and iodo-benzene in Sonogashira reaction. By Sonogashira polymerization, the ABtype monomer gave Myr-PMPE-1 ,in which the side chiral groups were distributed uniformly along the backbone. On the other hand ,the obtained AA type monomer was pelymerized with 1,4-diethynyl-2,5-dimyrtanoxybenzene to give Myr-PMPE-2, in which the distribution of the side chiral groups was alternatively crowd and loose. Both of these two polymers showed no CD signal in solution because of their good solubilities. Then, the investigations of chiroptical properties of these two polymers were carried out in the form of spin-cast films. The films were annealed above the glass temperature of the corresponding polymer, and the effects of annealing temperature and time on the properties ofthe films were investigated by UV-Vis absorption, fluorescence and circular dichroism spectra. The resuhs showed that annealing treatment had no significant effect on the properties of Myr-PMPE-1, including UV-Vis absorption, fluorescence and optical activity .The maximum absolute value of dissymmetry factor （│gmax│） was 1.62 × 10^-4 . On the other hand, annealing treatment significantly affected the properties of Myr-PMPE-2. Without annealing or being annealed below 100℃, the Myr-PMPE-2 films showed almost no Cotton effect. In contrast, when annealed above 120℃, the absorption and emission of Myr-PMPE-2 film slightly red shifted with increasing annealing temperature and annealing time, and most importantly, the intense of CD signals increased significantly, and the optical activity of Myr-PMPE-2 films increased obviously. After annealing at 140℃ for 4 h, │gmax│ of Myr-PMPE-2 film was up to 3.07 × 10^-3 ,about one order of magnitude higher than that of Myr-PMPE-1 film. These observations indicate that the substitution pattern of the chiral side groups has significant effect on the chiroptical properties of chirally substituted conjugated polymers. The obtained results can contribute to the design of chiral conjugated polymers with high optical activitv.