Liquid Crystalline Ionomers Containing Azobenzene Mesogens:  Phase Stability, Photoinduced Birefringence, and Holographic Grating

Abstract

Liquid crystalline (LC) ionomers containing azobenzene mesogens and three transition metal ions (Cu2+, Zn2+, and Mn2+) were prepared and characterized. Metal ions were found to exert significant effects on the photoinduced orientation of azobenzene mesogens and on the diffraction efficiency of holographic gratings. Using methacrylic acid for neutralization with metal ions, as compared with the copolymer with no metal, ionomers of Zn and Mn showed increased photoinduced birefringence and higher diffraction efficiency of birefringence gratings obtained by excitation with spatially modulated light polarization. By contrast, ionomers with Cu showed the opposite effects. As a whole, the behavior of photoinduced birefringence and holographic grating appears to be correlated with the thermal stability of the LC phase formed by azobenzene mesogens in the ionomer. Some new thoughts are discussed regarding the effect of metal and their ionic aggregates on the clearing temperature of LC ionomers. The interest for further exploring azobenzene LC ionomers is demonstrated by the finding that the insertion of a small amount of certain metal ions could be an effective means to improve or to tune the properties of azobenzene polymers.

Kinetics of photoinduced birefringence in the guest–host system of poly(methyl methacrylate) doped with azobenzene‐containing crown ethers

“…The appearance of the effect in azobenzene dye‐doped polymers and its possible use in information recording were demonstrated by Todorov and coworkers 5, 6. Later, the effect was also used in the formation of surface relief gratings,7–10 nonlinear optic applications,11–13 the photoinduced alignment of liquid crystals,14–18 and rewritable memory application,19 (see also a recent review20 and references therein).…”

Synthesis and mesomorphic properties of side‐chain liquid crystalline ionomers containing sulfonic acid groups

“…The methods employed by Gramain and coworkers 13 was based on simultaneous quaternization and polymerization of 4-vinylpyridine in the presence of a mesogenic group, which resulted in LCPs containing ionic charge. As for Vuillaume et al, 14 they prepared LCPs with side groups containing a pyridine-type unit, which was quaternized to form ionomers; Zhao and coworkers 15,16 have obtained LCIs containing metal ions (Cu 2þ , Zn 2þ , and Mn 2þ ) by partial neutralization of a copolymer from a mesogenic methacrylate monomer and methacrylic acid comonomer. Meanwhile, other researchers 17 had synthesized a series of new chiral nematic ionomers containing 0.7-9.0 mol % ions of alkali metals Na and transition metals Co(II).…”

Reconfigurable holographic interferometer with fixed mirrors

“…With increasing d, the ranges (9) narrow and, when their boundaries merge, q d = (1 − tan |ψ|)/2. The diameter d reaches its limit value d g for the given angle of incidence, ϕ (or α), this value is called the boundary value.…”

“…These are above all work on exploring new photosensitive materials: photopolymers [5,6], liquid crystals [7][8][9], colloidal suspensions of metal nanoparticles [10], organic and inorganic films [11,12], photorefractive crystals [13]; on designing memory, encoding and decoding devices based on multiplexed holograms [10,[14][15][16], controlled spectral optical filters [17], static Fourier transform spectrometers of visible and near-IR spectral ranges [18], oneand two-dimensional relief submicron rasters based on chalcogenide glassy semiconductors [19], and other applications, e.g., [20]. The above references do not exhaust the list of relevant studies of the issue but they are merely illustrative of the very wide range of possible applications of the HIFM.…”