Thermal stability and optical properties of aromatic polyimides containing side-substituted azobenzene groups

Abstract

Aromatic azopolyimides based on 9,9-bis [4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride and aromatic diamines containing substituted azobenzene group have been studied regarding their thermal and photooptical properties. The thermal analysis showed that the decomposition of these polymers takes place in two or three stages. The optical properties of the investigated polymers have been analyzed by transmission and reflectivity measurements within the spectral range of 200-2500 nm. Temperature dependence of absorption coefficient has been found on the basis of ''in situ'' transmission measurements, during annealing of thin films up to 300 C. It turned out that this process did not change the conjugation of polymer chain but caused a slightly more, irreversible structural disorder.

Post‐polymerization modification of polyetherimide by Friedel‐Crafts acylation: Physical–chemical characterization and performance as gas separation membrane

“…The TGA and derivative thermogravimetry (DTG) curves for the neat PEI and the acylated derivatives are shown in the Supporting information Figure S5 (a) and (b) and the results are summarized in the Table 2. It can be observed that, except for PD55 , all derivatives present one main degradation step, suggesting that the degradation mechanism did not change with the acylation (for some samples a weight‐loss event is observed below 300°C, which could be related to residual solvent and adsorbed moisture 15,31,32 . However, Table 2 shows that the degradation onset decreases as the size of the pendant acyl group increases.…”

“…It can be observed that, except for PD55, all derivatives present one main degradation step, suggesting that the degradation mechanism did not change with the acylation (for some samples a weight-loss event is observed below 300 C, which could be related to residual solvent and adsorbed moisture. 15,31,32 However, Table 2 shows that the degradation onset decreases as the size of the pendant acyl group increases. Nevertheless, all derivatives (except to PD55) present thermal stability at temperatures above 500 C and thus can be considered as high-temperature polymers (Figure S5 in the Supporting information).…”

Properties of some azo-copolyimide thin films used in the formation of photoinduced surface relief gratings

“…[15][16][17] Polyimides with azobenzene derivatives have already been investigated for photoinduced alignment in a liquid crystal display, 18 photomechanical response materials [19][20][21][22] and for holographic recording. [23][24][25] The most of the synthesized azopolyimides contain covalently attached chromophores mainly as side-groups of the polymer backbone [26][27][28][29][30][31][32][33] and only few papers report the preparation and characterization of polyimides with azobenzene derivatives placed in the main chain. 21,22,[34][35][36] It was expected that the incorporation of the substituted azobenzene units, connected in a special way (a part is in the main chain and the other part in the side chain) to the macromolecular chain of one aromatic polyimide, will keep and improve some properties of polyimide and will bring special properties of azobenzene moieties.…”

Characterization of poly(amic acid)s and resulting polyimides bearing azobenzene moieties including investigations of thermal imidization kinetics and photoinduced anisotropy

“…PIs with azobenzene derivatives have already been investigated for photoinduced alignment in a liquid crystal display, as photomechanical response materials and for holographic recording . The synthesized azo‐PIs contain covalently attached chromophores mainly as side‐groups of the polymer backbone . Only a few papers have reported the synthesis and investigation of PIs with azobenzene derivatives placed in the main chain …”