Design and Synthesis of Stimuli-Responsive Conjugated Polymers Having Azobenzene Units in the Main Chain

Abstract

Poly(p-phenyleneethynylene)-and heteroaromatic-containing poly(phenylene)-based conjugated polymers having photoisomerizable azobenzene units in the main chain were prepared using palladium-catalyzed cross-coupling reaction of 4,4′-diiodoazobenzenes with 1,4-diethynylbenzenes and bis(trimethylstannyl)heteroaromatics, respectively. Polymers possessing n-hexyl side chains on the aromatic rings were soluble in common organic solvents such as tetrahydrofuran, chloroform, and toluene. The polymers were thermally stable in air (T 0 > 330°C). Poly(p-phenyleneethynylene)-based polymers (3) and thiophene-, furan-, and N-methylpyrrole-containing poly(phenylene)-based polymers (5) showed remarkably red-shifted absorptions in the visible region (λmax > 400 nm) due to the extended main-chain conjugation, while the pyridine-containing poly(phenylene)-based polymer (5d) possesses a low degree of main-chain conjugation (λmax < 380 nm). Polymer 5d with low degree of main-chain conjugation showed reversible photoisomerization of azobenzene units, which was accompanied by the change in its electrochemical property.

Synthesis and self-assembly of side-chain azocomplex for preparation of solid and hollow nanosphere

“…But there is no main chain peaks in the area of 30~36 ppm. In addition, the total peak area of C 6 and C 7 equivalent to that of C 1 and C 2 , and the total area of C 9 and C 10 is as 1.8 times as C 8 . This suggests that the interaction between the acrylonitrile units and vinylpyridine units is weak.…”

“…Presently, various azobenzene-containing materials have been exploited by doping low-molecularweight azo dyes in polymers or covalent synthesis of azo polymers including side chain [6,7], main chain [8,9], and dendrimers [10]. However, doping films usually have low azo content due to poor compatibility, and the obtained photoinduction have been proved to be temporally unstable [11].…”

“…However, doping films usually have low azo content due to poor compatibility, and the obtained photoinduction have been proved to be temporally unstable [11]. Azobenzene-containing materials obtained from traditional chemical synthesis, compared with doped films, have better photoinduction stability; nevertheless, the synthetic processes usually were rigorous and fussy and involved many steps with low yield [6][7][8][9][10]. So the design of azo polymers with optimizing properties to satisfy different applications is still the most attractive target.…”

Synthesis, Photophysics and Morphology of a Conjugated Polymer with Azobenzene Building Block in the Backbone

“…There was no fluorescence observed, as most literature reported. [2][3][4]15,17,18 The excitation energy was consumed by the photoisomerization between trans and cis isomers for the azo compound, instead of emitting fluorescence. The monomer was found to have a sharp absorbance peaked around 350 nm, while the PPEPAPE in solution displayed a red-shifted, relatively broad absorbance with a peak around 450 nm and a shoulder around 330 nm.…”

Electrochromism in multichromic conjugated polymers: Thiophene and azobenzene derivatives on the main chain

“…In 2010 a study showed that azobenzene containing polymers can be used as the dispersing agents for carbon nanotubes [16]. Several conjugated polymers having azobenzene unit on the backbone were reported for interesting applications such as nonlinear optical devices, self structuring polymer films and photoresponsive polymers [17][18][19][20][21][22].…”