V. G. Syromyatnikov

Polymethacryloylaminoarylmethacrylates: New Concept of Photoalignment Materials for Liquid Crystals

New class of highly efficient polymers for liquid crystal (LC) photoalignment is proposed. These polymers are based on methacryloylaminoarylmethacrylates having two methacryloyl groups of different reactivity. The more active O-methacryloyl group is subjected to polymerization, while the less active NH-methacryloyl group undergoes photocrosslinking reaction in combination with Fries rearrangement. The latter process is anisotropic in case of polarized light irradiation that results in LC photoalignment with readily controlled pretilt angle and anchoring energy. The induced alignment shows high thermal and photo-stability.

New Photoalignment Materials in LCD's Development: Liquid Crystal Pretilt Angle Variations By Using Fluoroalkylmethacrylates

Fluorinated copolymers based on 4-(N-methacryloylamino)phenyl methacrylate are proposed as materials for the liquid crystal (LC) photoalignment with a wide range of variations of a pretilt angle. As fluorinated chains, 2,2,3,3-tetrafluoropropylmethacrylate and 2,2,3,3,4,4,5,5-octafluoropenthylmethacrylate are used. The growth of a pretilt angle with the concentration of fluorinated chains, more pronounced in a series with longer fluorinated chain, is observed. The pretilt angle of TN LC ZLI 2293 is smoothly varied in the range 0°–20°. Additionally, the uniform high pretilt angle (89°–90°) alignment is realized for VA LC MJ961180.

Photochemistry of Bis-Methacrylic Polymers and Alignment of Liquid Crystals

Photochemical processes leading to the photoinduced anisotropy and the excellent photoaligning properties of bis-methacrylic polymers are discussed. Comparing the data for bis-methacrylic polymers and a series of model compounds, we conclude that Fries rearrangements and crosslinking reactions taking place in bis-methacrylic polymers cause the photoinduced ordering in films of these polymers via the mechanism of photoselection. Thus, all of these photochemical processes contribute to the liquid crystal photoalignment. The induced alignment is thermally stable due to the crosslinking of methacryloyl groups which fix the induced anisotropy in aligning polymer films.

Problem of Photoalignment in the LCD's Development: Synthetic Routes in Its Solving

Hereinafter we discuss our last five years investigations in the field of new highly efficient polymers for liquid crystal (LC) photoalignment. New polymers finally proposed are based on methacryloylaminoarylmethacrylates with two methacryloyl groups of different reactivity. Fries rearrangement and photocrosslinking/photopolymeryzation are such photochemical reactions which take place in their films under the action of UV light. In a case of polarized light irradiation rearrangement results in LC photoalignment. The problem of pretilt angle and anchoring energy control as well as thermal stability of the induced alignment are discussed.

Naphthalene containing polymers as new photoaligning materials for LCs

Abstract Polynaphtylmethacrylates (PNMA) are considered as a new class of liquid crystal (LC) photoaligning polymers. The films of PNMA irradiated with polarized UV light provide high quality LC alignment with the easy axis oriented perpendicularly to polarization direction of the exciting light. A maximal value of the azimuthal anchoring energy was estimated as 5 × 10−6 J/m2. It is close to the best photoaligning materials. Fries rearrangement is considered as a main photochemical reaction leading to anisotropy of PNMA layers.

Photochemical Transformations in Bis-Methacrylic Polymers for Liquid Crystal Photoalignment: IR Spectroscopy Studies

Fourier transform infrared spectroscopy (FTIR) is applied to study photochemical transformations in poly(p-methacryloylaminophenyl methacrylate), a material with pronounced liquid crystal photoalignment capability. The characteristic bands corresponding to photosensitive groups of this polymer are identified by comparing its FTIR spectra with the spectra of model compounds having a reduced number of photochemical transformations. The changes in FTIR spectra of this material under ultraviolet illumination give evidence of two Fries rearrangements (in arylamide and arylester groups) and a conversion of C˭CH2 methacrylic bonds. This allows one to refine the microscopic model of photoinduced ordering in this class of polymers.

Effect of Polymer Molecular Structure on Photosensitivity of Composites Films Based on Infra-Red Polymethine Dye

The main results of studies of the effect of a polymer molecular structure on the photosensitivity of composites films based on infra-red polymethine dye photosensitive in a wide spectral range including the near IR region are presented. The highest photosensitivity is observed among the studied composites in that with a polyphenylenevinylene polymer matrix. The basic reason for high integral photosensitivity of these composites is the formation of aggregates, for which the energy and efficiency of the photogeneration of charge carriers are comparable or higher than those for quasiisolated molecules of polymethine dyes. The studied polymer composites of polymethine dyes can be used as near IR radiation sensors (800–1400 nm) and IR photoconverters including solar cells.

Nonlinear Optical Effects In Polymeric Azoesters

The methacrylic monomers containing azobenzene moiety with flexible alkyl spacers of different lengths and groups of different nature are synthesized, and their physicochemical properties were determined by electronic absorption, 1H NMR spectroscopy, and element analysis. In the present work, the homopolymers built with the use of the free radical polymerization of methacrylic monomers incorporating an azobenzene side-group have been synthesized and structurally characterized. The results of photochemical and optical activities of the corresponding polymers are presented. Third-order nonlinear optical (NLO) properties of the azopolymer solutions are studied by the degenerate four wave mixing (DFWM) method.

The Initial and Photoinduced 3D Orientational Order in Polymethacrylates with Azobenzene Side Groups

ABSTRACT The combination of the transmission null ellipsometry and total absorption method, earlier approved for several polymer classes, is applied to study 3D orientational configurations of azochromophores in polymethacrylates with azobenzene side groups. The transformation of the initial orientation due to the photoexcitation of azochromophores is investigated. The dependence of the orientational configuration on the structure of azochromophore fragments and its concentration in the polymers are also studied. In the non-irradiated films, azochromofores strive to be aligned normally to the film plate. Under irradiation, if reorientation mechanism of the photoinduced ordering prevails, the azochromophores reorient perpendicularly to the polarization direction of the exciting light, E ex, and in the saturation state they are randomly distributed in the plane perpendicular to E ex. This implies that the induced structure is mainly influenced by the photoordering, while selfordering of polymer chains is not effective or overcome, presumably because of high Tg of polymethacrylates. In case when photoselection ordering mechanism dominates, 3D distribution of azochromophores in the saturation state of irradiation is isotropic due to a strong exhaustion of the number of anisotropic trans isomers. The transient photoinduced orientations are biaxial independently on the dominating ordering mechanism. The reduction of the azochromophores concentration in polymers reduces the anisotropy rate but not influence the trends described above. The observed regularities were earlier described for several other classes of photosensitive polymers and so they may be common rules for photoordering in the photochromic media.

Photochemical Surface Modification of Polyethylene Films by New Azidobenzenesulfonamides

New azidobenzenesulfonamides are synthesized. Their photophysical and photochemical properties have been investigated. The photophysical properties of these compounds were investigated by 1H NMR, IR, and UV spectroscopy. The surface photomodification of polyethylene (PE) films by using new azidobenzenesulfonamides is carried out. The wetting angles for three liquids of different polarities (water, formamide, and diiodomethane) have been studied to estimate the surface modification performed. The obtained wetting angles are used for the determination of the surface free energy γS (γ), as well as its polar , dispersive Owens–Wendt , Lifshits–van der Waals γLW, and acid-base γAB components, by applying the Lifshits–van der Waals/acid-base methods.