Synthesis and conformation effects of poly(phenylacetylene)s having chiral and racemic polylactide pendants

Abstract

Chiral and racemic macromonomers with a polymerizable phenylacetylenyl end group (PA-PLLA and PA-PDLLA) were successfully synthesized through living ring-opening polymerization of chiral and racemic monomers (L-lactide and DL-lactide), respectively. Then the homopolymerization of PA-PLLA and PA-PDLLA was successfully carried out to give poly(PA-PLLA) and poly(PA-PDLLA), respectively. Chiroptical properties, hydrodynamic radii and micromorphologies of poly(PA-PLLA) and poly(PA-PDLLA) were analyzed via circular dichroism, dynamic light scattering and atomic force microscopy (AFM), and the conformation of the polymers is discussed. The results indicate that poly(PA-PLLA) induced Cotton effects with different intensities in various solvents, and its hydrodynamic radii and dispersity were also different in various solvents, while poly(PA-PDLLA) induced no Cotton effects and its hydrodynamic radii and dispersity were approximately the same in various solvents. Furthermore, a helical conformation of poly(PA-PLLA) and the random main chains of poly(PA-PDLLA) were observed by AFM. Therefore, it is concluded that poly(PA-PLLA) possesses a dynamic one-handed helical conformation in various solvents due to chiral poly(L-lactide) pendants, while poly(PA-PDLLA) possesses racemic main chains because of the racemic poly(DL-lactide) pendants. Copyright © 2012 Society of Chemical Industry