Helicity Induction in a Poly(phenylacetylene) Bearing Aza-18-crown-6 Ether Pendants with Optically Active Bis(amino acid)s and Its Chiral Stimuli-Responsive Gelation
Helicity Induction in a Poly(phenylacetylene) Bearing Aza-18-crown-6 Ether Pendants with Optically Active Bis(amino acid)s and Its Chiral Stimuli-Responsive Gelation
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DOI：
10.1021/ma047303o
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发表时间：
2005-03
期刊：
影响因子：
5.5
通讯作者：
K. Morino;M. Oobo;E. Yashima
中科院分区：
文献类型：
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作者：
K. Morino;M. Oobo;E. Yashima
以氮杂-18-冠-6醚为侧基的有规立构聚苯乙炔（poly-1）与光学活性的双（氨基酸）如高胱氨酸高氯酸盐（1 -2）在乙腈中络合时形成主要的单手螺旋构象，络合物溶液随时间逐渐凝胶化。该凝胶在聚合物主链区域表现出诱导圆二色性（ICD），但ICD强度的绝对值随着温度的升高而降低，并且凝胶在55 °C熔融之前逐渐收缩。这种凝胶-溶胶转变是不可逆的，但是一旦溶液在60 °C下退火，然后迅速冷却到0 °C，凝胶的形成在环境温度下再次发生。poly-1−l-2凝胶在外部刺激下收缩，例如添加不良溶剂。对映体过量（ee）的2上的螺旋诱导聚-1及其凝胶化的效果也进行了研究。当2的ee值为60%时，poly-1显示出与2类似的强CD。
A stereoregular poly(phenylacetylene) bearing the aza-18-crown-6 ether as the pendant (poly-1) formed a predominantly one-handed helical conformation upon complexation with optically active bis(amino acid)s such as l-homocystine perchlorate (l-2) in acetonitrile, and the complex solution gradually gelled with time. The gel exhibited an induced circular dichroism (ICD) in the polymer backbone region, but the absolute value of the ICD intensity decreased with an increase in temperature and the gel gradually shrunk before melting at 55 °C. This gel−sol transition was irreversible, but once the solution was annealed at 60 °C and then rapidly cooled to 0 °C, the formation of the gel occurred again at ambient temperature. The poly-1−l-2 gel shrunk in response to external stimuli such as the addition of a poor solvent. The effect of the enantiomeric excess (ee) of 2 on the helicity induction in the poly-1 and its gelation was also investigated. In the presence of 60% ee of 2, poly-1 showed an intense CD like tha...