Large and highly stable photoinduced birefringence in poly(amideimide)s with two azochromophores per structural unit

Poly(amic acid)s and their poly(amide imide) counterparts containing azobenzene moieties: Characterization, imidization kinetics and photochromic properties

“…However, no clear correlation between the structure of the chromophore located between the amide groups and the maximum birefringence level can be seen. The maximum birefringence generated in PI-2 and PI-3 is as large as that reported for poly(amide imide)s of the same main chain structure containing two identical chromophores in the repeating unit with either CH 3 , OH or H substituent [22]. Thus, taking the above into account it can be suspected that both of the chromophores (i.e., also the AKFNO 2 one) present in the repeating unit of PI-2 and PI-3 isomerize and reorient under the linearly polarized writing beams.…”

“…4 for the films of poly(amide imide)s with two azochromophores in the repeating unit the absorption range in not as wide as it might be expected. It can be connected with the incorporation of the azo-dye into the polymer chain and with the changes in electronic environment of the chromophore, what can influence on the UVeVis spectra [21,22]. Similar effect was also found for PAA films.…”

“…Detailed synthesis and characterization of the chromophores 2,4-diamino-2 0 -fluoro-5 0 -nitroazobenzene (AKFNO 2 ), 2,4-diamino-4 0 -methylazobenzene (AKCH 3 ) and 2,4-diamino-4 0 -hydroxyzobenzene (AKOH) have been reported previously [18,21,22].…”

“…for PI-2 and PI-3 is as low as that observed for the poly(amide imide)s presented in Refs. [22], what was associated with a main chain rigidity and a rigid connection between the azo-dye and the backbone. Present studies show that even in the case of the polymers with the open imide ring the rate of the birefringence relaxation within 600 s is similarly low.…”

Thermal, optical and photoinduced properties of a series of homo and co-polyimides with two kinds of covalently bonded azo-dyes and their supramolecular counterparts

“…Moreover, the supramolecular systems based on H-bonds were characterized by a faster growth of the Dn than analogue functionalized polymers. Low values of the Dn and a high relaxation of photoinduced birefringence of polymers containing azo-chromophores bonded by flexible chain indicates, that more promising materials for induction of the Dn are azo-polymers containing covalently bonded choromophores, where one of the aromatic rings is incorporated to the main-chain of the polymer [56,57]. The influence of a kind of connection of chromophore and a kind of polymer matrix was clearly observed by using the irradiation wavelength of 445 nm, when only the DR13 azochromophore was excited.…”