New Optically Active Methacrylic Polymers Bearing Side‐Chain Bisazoaromatic Moieties

Abstract

The synthesis of three novel optically active monomers containing a side‐chain chiral moiety linked to a photochromic bisazoaromatic chromophore, such as (S)‐3‐methacryloyloxy‐1‐[4′‐phenylazo‐(4‐azobenzene)]‐pyrrolidine [(S)‐MPAAP], (S)‐3‐methacryloyloxy‐1‐[4′‐cyanophenylazo‐(4‐azobenzene)]‐pyrrolidine [(S)‐MPAAP‐C] and (S)‐3‐methacryloyloxy‐1‐[4′‐nitrophenylazo‐(4‐azobenzene)]‐pyrrolidine [(S)‐MPAAP‐N], is described. Each monomer has been radically homopolymerized to afford the corresponding optically active polymeric derivative, which have been characterized, in solution and in the solid state, and their properties compared to those of the monomers and of analogous homopolymers bearing only one azoaromatic chromophore in the side chain. The optical activity displayed by the polymers is discussed in terms of extent of chiral conformation assumed by the macromolecules as a consequence of their stiffness and the dipole‐dipole interactions between the bisazoaromatic chromophores.magnified image

Rewritable and switching chiroptical supramolecular nanolayers

“…57 Introduction of a chiral centre in the polymer side group is shown to give rise to greater steric preference for helical configurations 22,14 (in contrast to helical disordering reported for achiral azobenzene chromophore side groups during cis-trans transitions 7,22 ). In fact, azobenzene derivatized polymers which contain multiple or constrained chiral centres 14,22 (such as pyrrolidine groups 70 ) produce enduringly stable (with enhanced polymer matrix order) helical orientated segments (lasting up to several weeks 22,14 ), which is consistent with the prolonged longevity of the present azobenzene derivatized plasmachemical nanofilms (still stable after 6 months). The chiroptical supramolecular switching performance observed in this present study displays no deterioration in response and exhibits stable supramolecular configurations amenable to enantiomeric toggling, 71 Fig.…”

Photoresponsive polymers with multi-azobenzene groups

“…In addition, polymethacrylates with similar structures have been synthesized and their photoresponsive properties, such as photoisomerization, 91,105-112 photo-alignment, 106,107,110 photoinduced birefringence, 91,105,106,[108][109][110]113 information storage, 112 and the induction of helical chirality, 111,114,115 have been investigated. The rate of photoinduced birefringence for the bis-azopolymers was slower than that for monoazopolymers, 90,91 while the birefringence values for bisazopolymers were higher and the birefringence stability for bis-azopolymers was better than those for monoazopolymers.…”

Supramolecular Chirality in Azobenzene-Containing Polymer System: Traditional Postpolymerization Self-Assembly Versus In Situ Supramolecular Self-Assembly Strategy

“…It should be noted that these works are preliminary explorations of chirality on the side-chain Azo-polymers in solution, which involves the ordered arrangement of azoaromatic chromophores in a helical geometry with one prevailing chirality. The Azo-polymer derivatives 5 also showed optical activity as demonstrated by the presence of strong exciton couplets in the CD spectra, with a mechanism similar to Azo-polymer derivatives 4 [ 151 , 152 , 153 ]. These fascinating works indicate that, in addition to the asymmetric chiral center present in the side group, the helical chirality of the Azo-polymer backbone can also be constructed in solution when the chiral center is close to the methacrylate main chain.…”