Effect of amino acid pendant groups on the helical configuration of polyphenylacetylene

In this study, several polyphenylacetylenes (PPAs) derivatives containing amino acid pendant groups were synthesized using a rhodium system catalyst (Rh(nbd)BPh₄). The synthesized derivatives of PPAs included single chiral PPA with a single chiral center in the pendant groups and double chiral PPA' with two chiral centers in the pendant groups. The PPA and PPA' showed strong circular dichroism (CD) signals in the main chain absorption region of the UV-vis spectrum, while the monomer showed no CD signals. Furthermore, the PPA and PPA' with different chiral pendant groups showed different Cotton effects in the CD spectra. The results showed that these polymers existed in helical conformation, and the chiral center of the pendant groups affected the polymerization and helical structure of PPAs.

本研究采用铑系催化剂（Rh(nbd)BPh₄），合成了多款含氨基酸侧基的聚苯乙炔（polyphenylacetylenes, PPAs）衍生物。所合成的PPAs衍生物分为两类：一类为侧基带有单个手性中心的单手性聚苯乙炔，另一类为侧基带有两个手性中心的双手性聚苯乙炔（PPA'）。单手性聚苯乙炔与双手性聚苯乙炔（PPA'）在紫外-可见光谱的主链吸收区域呈现出强烈的圆二色性（circular dichroism, CD）信号，而其对应单体则未检测到CD信号。此外，带有不同手性侧基的PPA与PPA'在圆二色谱中展现出各异的科顿效应（Cotton effect）。研究结果表明，此类聚合物以螺旋构象存在，且侧基的手性中心会对聚苯乙炔的聚合过程与螺旋结构造成影响。