Stimuli-Responsive Helical Poly(phenylacetylene)s Bearing Cyclodextrin Pendants that Exhibit Enantioselective Gelation in Response to Chirality of a Chiral Amine and Hierarchical Super-Structured Helix Formation

Abstract

Novel poly(phenylacetylene)s bearing a β-cyclodextrin (CyD) residue connected to the phenyl ring through an ester (poly-2β) and an ether linkage (poly-3β) as well as an amide linkage (poly-1β) were synthesized and their chiroptical properties were investigated with circular dichroism (CD) and absorption spectroscopies. The chiroptical studies demonstrated that the linkage groups play an important role in the conformational change induced by external chiral and achiral stimuli, such as temperature, solvent, and interactions with a chiral amine. Poly-1β and poly-2β showed a unique enantioselective gelation in response to the chirality of a chiral amine, and the polymers further formed hierarchical superstructured helical assemblies on a micrometer scale with a controlled helix sense, as evidenced by the scanning electron microscopy observations.