In the present study we investigate the use of polymer liquid crystal for holographic recording. Holographic patterns were produced by means of two-beam interference using an Ar+ laser. The polymer liquid crystal thin layers were prepared by injecting RM257 into cells through capillary action at 140¢XC where the RM257 mesogen was in isotropic state. By exposing the mesogenic layer to the laser interference patterns, we have successfully imprint holographic patterns into RM257 thin layers. In order to reach the best alignment, the intensity of laser beam, sample temperature, the spacial period and exposure time must be properly set.

RM257 consists of photoactive mesogenic end groups. By in situ polymerization of the mesogen, the optical information can be recorded into RM257 thin film. In this study, the RM257 thin films were exposed to a holography irradiation created using an Ar+ laser. The holography patterns have been found to be imprinted into the polymer thin films. The refractive efficiency can be increased when the sample temperature is properly controlled during holography irradiation. The work was started from the use of two beam interferometry, and further to use three beam interference. The molecular arrangement in the resultant polymer film and their function in optical modulation have been studied.

Discotic liquid crystal (LC) molecules have a structure that is comprised of a rigid aromatic core with side-chain molecules. Intermolecular £k-£k interactions force the tube to orient and form one-dimensional columnar structures which can act as molecular wires. In recent years, discotic LC molecules have been deposited on surfaces from solution to create the solid-state electronic elements used widely in solar cells, organic light-emitting diodes (OLED), organic photovoltaic, field-effect transistors (FET), and molecular wires. Different stacking morphologies can change the behavior of the material and thus will have potential for different applications. Hence, effective control over the stacking of the LC molecules on surfaces is important for optimizing the performance and effectiveness of LC-based electronic components and devices. This study has focused on LC molecules with acid and ester containing functional groups, and how these groups influence the stacking behavior on surfaces. Here, the self-aggregation behavior of the discotic LC ester in solution was investigated quantitatively by determining the concentration dependence of the 1H NMR chemical shifts. Our results showed that discotic LC ester has different self-aggregation behavior in CH2Cl2, THF and Benzene organic solvents. THF solvent showed the highest degree of aggregation, followed by CH2Cl2, and then benzene. We also studied the effects of (i) different solvents (THF, CH2Cl2, and Benzene), (ii) different surface functional groups (OH, CH3, NH2, SH, and diphenyl), and (iii) temperature, on the stacking phenomenon of discotic LCs on silicon surfaces. In part (i) our results showed that discotic LC ester had different morphologies on silicon surfaces due to differences in solvent polarity and evaporation rate. In part (ii), we observed that different surface functional groups did not affect the intermolecular interaction between either the ester- or acid-type LC molecules. For the acid-type LC, strong hydrogen bonding interactions with the surface caused the crystals to form rod-like fiber structures. However, the ester-type LC molecules formed ribbon-like stacks on the surfaces. For functional groups containing CH3 (more hydrophobic surfaces), we observed no LC molecules on the surface, which was likely due to the poor wettability of the solvents on OTS. In part (iii), we observed that both acid and ester discotic LCs formed large aggregates on the surfaces due to a ¡§ripening effect¡¨. With increased temperature, the molecules were able to overcome the wetting interaction with the surface and self-aggregate into three-dimensional clusters.

No description available.

A series of phenanthrene and oxidized phenanthrene derivatives with typical substitution patterns, 1.31, 1.32, 2.30a-f, 3.1a,b and (-)-4.1 have been synthesized as liquid crystal cores by a combined Directed ortho Metalation (DoM), cross coupling and Directed Remote Metalation (DreM) strategy. The synthetic methodology employed allowed variation of the tail and core structures, for the preparation of a new smectic liquid crystal compound (1.32), a homologous series of 9,10-dihydrophenanthrene-9,10-diones (2.30a-f), a diastereomeric trans-9,10-dihydrophenanthrene-9,10-diol (1.31), two enantiomeric 9,10-dihydrophenanthrene-9,10-diones (R)-3.1a-b) and an enantiomeric 9,10-dihydro-9,10-dimethylphenanthrene-9,10-diol ((-)-4.1). Polarized microscopic and differential scanning calorimetric measurements suggest that 1.31 forms a large range of SmC phase, ca. 100 ºC, followed by a small range of nematic phase, ca. 10 ºC; the 2.30a-f series show similar mesogenic properties, but with the extension of the length of a side chain from six carbons to eleven carbons, the nematic phase has disappeared (in the cases of 2.30a-c). Although (R)-3.1a-b and (-)-4.1 are not liquid crystals, they show ferroelectric induction by doping, in the amount of ca. 5 mol%, into unchiral liquid crystal hosts PhB, DFT, PhP1, NCB76 and 2.30f. However, due to the detection limit of the instrument, i.e., ca. 0.5 nC/cm2, the spontaneous polarizations (Ps) induced could not be measured. / Thesis (Ph.D, Chemistry) -- Queen's University, 2009-08-17 15:52:54.612

No description available.

Currently, alignment films for use in liquid crystal displays are produced via a mechanical rubbing process. The dust produced by mechanical rubbing along with problems due to friction and uneven roller pressure lead to defects in the display. Therefore a novel method for aligning polymers films by irradiation with polarised light has been attempted. Anisotropy introduced into the films by selective irradiation affects liquid crystal alignment. The polymers used in this study are poly (vinyl cinnamate), poly (9- anthraceneoate ethyl methacrylate) and poly (p-azidobenzoate ethyl methacrylate). Poly (vinyl cinnamate) is a classical photoresist polymer which undergoes a [2+2] photocycloaddition in the presence of UV light. Poly (9-anthraceneoate ethyl methacrylate) and poly (p-azidobenzoate ethyl methacrylate) are both novel polymers which have the potential to undergo photo-crosslinking reactions. Poly (9-anthraceneoate ethyl methacrylate) contains an anthracene-terminated side chain which dimerises under the influence of UV light introducing anisotropy into the system. Poly (p-azidobenzoate ethyl methacrylate) contains an azido group which when irradiated with polarised light loses nitrogen to yield nitrenes which can combine to form azobenzene species. UV spectroscopy, infrared dichroism studies, birefringence measurements and fabrication of a simple liquid crystal cell show that poly (vinyl cinnamate) and poly (9-anthraceneoate ethyl methacrylate) undergo selective photoreaction. Poly (p- azidobenzoate ethyl methacrylate) is shown to undergo reaction but not to give the desired products.

No description available.

In this project a number of synthetic procedures were investigated with a view to preparing a new type of charge transfer polymer system having a structure based on that of side chain liquid crystal polymers, in that the hoped for polymer was composed of charge transfer acceptors connected to a polymer backbone via a flexible alkyl spacer linkage. As part of this work new charge transfer complexes were prepared some of which have shown possible novel properties, such as, co-operative magnetic effects and film forming capabilities. Finally, in order to characterise materials prepared, a Faraday magnetic susceptibility balance and instrumentation for measuring electrical conductivity has been built.

In 1970, Freiser made the theoretical prediction that a biaxial nematic phase could exist. In auniaxial nematic, only one particle axis is aligned but with a biaxial nematic, all three molecular axes are aligned. This phase is expected to occur for particle whose shape is intermediate between that of a disc and a rod. Board and bent-core particles are examples of such structures. Despite extensive experimental investigation, however, very few biaxial nematic systems have been found. Yu and Saupe [21] have shown the occurrence of a biaxial nematic phase generated for a lyotropic system. Similarly van der Pol observed a biaxial nematic phase in a colloidal suspension of board-like goethite particles [22]. For thermotropic, molecular systems, however, the situation is less clear-cut. Merkel et al., [23] and Figueirinhas et al., [24] claim that Tetrapodes have can exhibit a biaxial nematic phase, whilst Acharya et al., [25] and Prasad et al., [26] have also suggested the occurrence of this same phase with bent-core molecules, though experimental uncertainty still exist. With regards to theoretical predictions of the biaxial nematic transition, one notes in particular the work of Taylor and Herzfeld [13] on hard sphero-platelets, which predicts a rich phase diagram, notably containing an unusual discotic smectic phase. To date there are few simulations of board-like models, such as Vanakaras et al., [27] being arecent exception, developing a phase diagram for hard board-like colloids. Similarly, Escobedo[28] has produced a phase diagram of hard cuboids. We present molecular dynamics simulation results on a short range repulsive fused-hexagonmodel, somewhat resembling hard boards. Depending on the geometry of the board, we observe uniaxial and biaxial nematics, smectics A and C, a biaxial smectic phase and a columnar phase. Possibly the most interesting result is the existence of the theoretically predicted discoticsmectic. We further investigated the effect of applying both external fields and shears to several of the structures. The former, among other things, aided the alignment of the particles in the phase, removing dislocations. The shear was also seen to increase biaxial ordering, however, it also demonstrates an ability to introduce clear layer fractures, seen when shearing forces became overly dominant. An applied electrical field was able to induce isotropic!biaxial nematic and biaxial smectic switching. Finally we consider briefly less-symmetric arrangements of fused hexagons, including chiral particles. These systems proved hard to equilibrate but discotic nematic phases were observed for certain structures. Chiral clusters were also observed, however, no globally chiral phase was found. Columnar structures were also seen, but showing a weak overall alignment as columnstended to point along several directions.