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.