Synthesis of chiral polyacetylenes carrying amino acids and azobenzenes and transformation of the higher order structure by photoirradiation

Abstract

This study examined the synthesis of copolymers of an alanine‐derived chiral N‐propargylamide [N‐(tert‐butoxycarbonyl)‐L‐alanine N′‐propargylamide] with an azobenzene‐containing N‐propargylamide [N‐4‐(phenylazo)benzoyl‐L‐alanine N′‐propargylamide] and the transformation of the higher order structure of the copolymers by photoirradiation. The trans‐azobenzene moiety of the copolymers isomerized into the cis one, which was accompanied by the transformation of the helical structure into a random state by UV irradiation. Visible‐light irradiation induced the reisomerization of cis‐azobenzene into the trans one, but it did not induce the recovery of the higher order structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4641–4647, 2004

Synthesis of novel helical poly(N-propargylamides) containing azobenzene pendant groups and effects of substitution groups on azobenzene on the stability of helix

“…4(C)) of Poly(V 3 ) barely changed with the temperature rise. The helical stability of Poly(V 3 ) was better than that of the reported poly(N-propargylamides) carrying azobenzene moieties at 50°C in THF [6,31]. All of them did not contain substituents on the azobenzene.…”

“…This meant that the main chains of Poly(V 1,3 ) had stable helical structures after the trans-cis isomerization of the azobenzene group. Most reported poly(N-propargylamides) bearing azobenzenes could not maintain stable helical conformation upon UV irradiation, and only a few of them showed the similar CD effects [6,[30][31][32]. The new designed azobenzene moieties in the side chains of Poly(V 1,3 ) strengthened hydrogen bonding, and increased steric repulsion and electrostatic interaction between the side chains, which diminished the effect of trans-cis isomerization of azobenzene on the helical structure of the main chain.…”

“…Synthesis and precise control of optically active helical polymers have received considerable attention in the past decades due to their unique structures, chiroptical properties and many important applications in chiral discrimination, chiral separation, enantioselective catalysis, chemical sensor, and optical liquid crystalline materials [1][2][3][4][5][6][7][8]. In nature, the helical conformation of biomacromolecules plays very critical role in organism (e.g., DNA or protein).…”

“…Many polymers bearing azobenzene chromophores have been explored extensively because of the unique optical properties [25][26][27][28][29]. Recently, some helical poly(N-propargylamides) containing azobenzene moieties have been synthesized, and the reversible transformation of higher order structures triggered by azobenzene isomerization were studied [6,[30][31][32]. Sanda and coworkers synthesized the helical poly(N-propargylamides) bearing designed azobenzene moieties.…”

Chiroptical study and conformation analysis of helical polymers surrounded by helical hydrogen-bonding strands

“…This biomimetic way of helix formation may develop a new methodology of designing synthetic helical polymers. We have incorporated a wide variety of pendent groups into poly(N-propargylamides) including linear and branched alkyl groups [9], aryl groups [10], hydroxyl groups [11], carboxyl groups [12], cyclics [13], esters [14], photo-responsive [15] and photoluminescent groups [16] to find that the stability and sense of the helical structure are tunable with external stimuli such as polar solvents, pH, heat and light. In the course of our study on a series of poly(N-propargylamides), we have examined the chiroptical properties of poly(N-(3-butynyl)amide), an analog of poly(N-propargylamide), to find it exhibits a completely different CD spectroscopic pattern from that of poly(N-propargylamide) [17].…”