Synthesis, optical activity, and liquid crystallinity of polyacetylenes containing naturally occurring building blocks

Poly(phenylacetylene)s and poly(1-alkyne)s containing naturally occurring building blocks are designed and synthesized. The monomers are prepared in moderate to high yields by multi-step reactions. Polymerizations of the monomers are effected by classical metathesis catalysts of MoCl5 and WCl 6, and organorhodium complexes of [Rh(nbd)Cl]2, [Rh(cod)Cl] 2, and Rh(cod)(NH3)Cl, giving high molecular weight polymers in high yields. The structures and properties of the polymers are well characterized and evaluated by IR, NMR, UV, TGA, DSC, POM, XRD, and CD analyses. All the polymers possess high thermal stability (≥ 300°C). The amino acid pendants have endowed the polymers with novel optically active properties. The chirality transcription from the appendages induces the chain segments of the polymers to helically spiral predominantly in one preferred direction. The bulky pendant terminal groups stabilize the helical conformation against external perturbations such as solvent and temperature. The chain helicity of the polymers can be manipulated by varying their molecular structures and external perturbations such as solvent and acid. By tuning the backbone rigidity and pendant interaction through molecular engineering endeavor, optically active and liquid crystalline polyacetylenes with sterol side chains are successfully prepared, whose properties have been found to vary dramatically with the backbone structure and the mesogenic pendants.