Preparation and characterization of green reflective films of polyaniline analogs containing azobenzene units

Abstract

Pd-catalyzed polycondensation of aniline derivatives and 4,4 0 -dibromoazobenzene affords polyaniline analogs containing azobenzene units. The polymers are red in solution and in thin films state, whereas they have a green luster in thick films. Substitution of 4,4 0 -dibromoazobenzene for 4,4 0 -dibromostilbene changes the reflection color from green to blue, whereas the introduction of a non-conjugated unit slightly affects the reflection color. The glossiness of the film is dependent on the smoothness of the film surface. The reflectance measurements using polarized light reveal that reflection spectra correlate well with the complex refractive index (ñ 5 n 1 ik) of the film. These results confirm that the green luster can be attributed to the uniform surface reflection of the object, which has a large refractive index and absorption coefficient at around 500 nm. The polymer films exhibit good transmission of radio frequency signals owing to the lack of free electron carriers.

Self-assembled conjugated polymer spheres as fluorescent microresonators

“…In the present research, we further find that π -conjugated copolymer 4 (Fig. 1d)2829, consisting of azobenzene and aniline repeating units, also forms well-defined microspheres quantitatively.…”

Microwave-assisted polycondensation of 4-octylaniline with dibromoarylene

“…We previously reported the polycondensation of 4‐octylaniline with 4,4′‐dibromoazobenzene; the reaction gave the corresponding poly(arylamine), Polymer 1 , with a molecular weight of 18,900 in 95% yield under the optimized conditions via conventional heating (Scheme , Table , Entry 1). Accordingly, the investigation regarding the microwave‐assisted reaction began with this polycondensation reaction, and various fundamental parameters of the reaction were tested in order to gain insight into the effect of microwave heating; the results are summarized in Table .…”

“…Poly(arylamine)s have generally been prepared by polycondensation via the Pd‐catalyzed aryl amination of aromatic amines with dibromoarylenes, known as the Buchwald–Hartwig reaction; these reactions have provided a variety of poly(arylamine)s in good yields under mild conditions . On the other hand, microwave heating is known to promote efficient organic reactions including transition‐metal catalyzed cross‐coupling reactions .…”

Synthesis of methyl‐substituted azobenzene–carbazole conjugated copolymers with photoinduced structural changes

“…According to the previous paper, molecular weight and effective conjugated length of the main‐chain‐type azobenzene polymers influence progress of the photoisomerization . Synthesis of main‐chain‐type azo‐polymer films prepared by Pd‐catalyzed polycondensation having colored surface with metallic luster and its application as a reflective film has been reported . Several phenomena, such as “molecular accordions” showing molecular shrink and elongation repeatedly upon light irradiation and “molecular zippers” having a function of repeat opening and closing, have been reported.…”