Stimuli‐responsive polymers. VII. Photomodulated chiroptical switches: Periodic copolyaramides containing azobenzene, phenylene, and chiral binaphthylene main‐chain linkages

Abstract

Abstract Conformationally restricted copolyaramides containing a combination of 4,4′‐azobenzene, 1,4‐phenylene, and chiral 2,2′‐binaphthylene main‐chain segments exhibit photoresponsive chiroptical behavior stemming from multiple trans‐cis‐isomerization reactions triggered within their polymer backbones. In contrast to their more randomly constructed counterparts, copolymer variants endowed with periodic backbone structures undergo reversible, wavelength‐dependent inversions in their optical rotations in response to multiple ultraviolet‐light/visible‐light illumination cycles. Similar behavior is also observed for a smaller oligomer fitted with a periodic arrangement of its monomer units. In their present forms, the periodic constructs constitute a new class of solution‐based, photomodulated chiroptical switches that may be suitable for applications in a number of emerging technological areas. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 566–577, 2004