Main Chain-Containing Azo-Tetraphenyldiaminobiphenyl Photorefractive Polymers

Abstract

The design of polymeric materials with optimized photoconductivity and nonlinear optical properties is of major interest for emerging optical applications using photorefractive properties. This paper reports the synthesis and preliminary optical characterization of a series of novel, fully functionalized, photorefractive polymers. They were synthesized by a post azo coupling reaction of a polyether carbonate polymer based on the charge transport N,N,N‘,N‘-tetraphenyl-diaminobiphenyl group with 4-nitrobenzene-diazonium tetrafluoroborate by phase transfer catalysis. The amount of the inserted 4-nitro-phenyl-azo group was between 0.1 and 1.7 per structural unit. These polymers absorb in the UV−vis range, because of the presence of donor−acceptor substituted azobenzene chromophores. Light induced change of the refractive index was studied by birefringence measurements (λprobe = 632.8 nm) as a function of azo content in thin films with thickness ranging from 200 to 500 nm. Surface relief grating inscription was also demonstrated in the same polymer thin films, with a weak surface relief amplitude and a low diffraction efficiency (<1%). These results indicate a relatively low mobility of the azobenzene chromophores. Photoconductivity was studied by measuring the photocurrent through 40 μm thick samples where a metal-free phthalocyanine layer deposited on electrodes served as charge generator. These samples have exceptionally high photoconductivity compared to other composite materials. In addition, preliminary two-beam coupling experiments demonstrated unambiguously the photorefractive effect under low poling field (2.5 V/μm) at room temperature, but no net gain was obtained because of a high absorption coefficient at 632.8 nm.

Preparation of nano‐ and microparticles through self‐assembly of azobenzene‐pendent ionomers

“…[12][13][14] Azobenzene derivatives have two important properties, i.e., a nonlinear optical property and photoresponsive isomerization. [15][16][17] Many research groups have studied the thin film preparation from azobenzene-containing polymers and their application to the optical devices. 18 -20 However, to our knowledge, only Wang's group reported the preliminary particle preparation from azobenzene-containing ionomers.…”

Azobenzene Polymers for Photonic Applications

“…The dendron had a first-order molecular hyperpolarizability 20 times larger than the monomer. With regard to applications, the azos have been shown to function as electro-optical switches (Yamane et al, 1999) and exhibit photorefraction (Iftime et al, 2002;Steenwinckel et al, 2001;Barrett et al, 1998;Ho et al, 1996), an NLO effect where photoconductivity permits light to establish a space charge grating, whose associated index grating refracts a probe light beam.…”

Photoinduced Holographic Gratings in Azobenzene-Functionalized Poly(amideimide)s

“…25 Monomer DA shows three absorption maxima at 262, 298 nm attributed to the benzene ring and carbonyl groups and a peak located at 391 nm which is assigned to the vibronic coupling between n-% Ã and %-% Ã electronic transition of the trans azobenzene moiety. 33 Absorption spectra of polymers obtained from dianhydride DA, i.e., PI 4 and PI 5 exhibit two absorption bands one centered at about 262 nm and second very broad band at about 334-407 nm with shoulder. To find the position of the shoulder the second derivatives method was used (i.e., the maximum of the second derivative of absorption corresponds the absorption maximum).…”