A new series of side-chain polymers for alignment layers in liquid crystal displays (LCD) promoting a stable vertical alignment (VA) is presented. These materials are easy to process (no curing required), easy to be stored and transported. They are appropriate especially for LCDs with plastic substrates.

A method for a continuous control of the pretilt angle of the easy axis in the range 0–90° degrees and of the anchoring strength by using nanostructured polymers as alignment layers is described. The nanostructured polymers are blends of two different side-chain polymers each of them promoting planar and homeotropic alignment, respectively. A model to interpret the alignment of a nematic liquid crystal induced by such polymer layers is proposed. We show that in this case the anisotropic part of the surface tension can be approximated by a simple extension of the Rapini–Papoular expression. The predicted trend of the pretilt of the easy axis versus the concentration of the side-chain polymer promoting the planar alignment, for instance, is in good agreement with the experimental data. We also show that the effective anchoring strength of the system depends on the concentration of the side-chain polymer promoting planar alignment, and exhibits a minimum for a well-defined value of this quantity. The results obtained in this work seems to be of importance for liquid crystal displays technology since the control of the pretilt and the anchoring strength strongly affect the performance of liquid crystal displays.

By employing a nano‐engineering approach, nano‐structered polymers were designed, synthesised and used as materials for alignment layers in LCDs. Such materials make possible to control the molecular tilt angle in a broad range, from 0° to 90°, and they seems to enable the control of the anchoring strength as well.

A new series of dimeric chiral antiferroelectric materials using a trisiloxane as the central connecting linker and having fluorinated tails has been synthesized together with their corresponding monomers. Spacer lengths of 3–6 and 11 methylene groups were used. As a comparison to see the effect of the siloxane length on the phase behaviour, one dimer with a tetrasiloxane core was also synthesized. Monomers with 3–6 carbons in the spacer showed just orthogonal smectic phases and only the long 11 carbon spacer 7F4PPB11 showed tilted phases in a very similar way to what was found in the unfluorinated monomers previously studied. All trisiloxanes showed a high temperature antiferroelectric phase and those with a spacer length of 4 or more carbons also showed one or two columnar antiferroelectric phases when decreasing the temperature. The spontaneous polarisation Ps was high, especially in the columnar phases where it ranged from 800–1200 nC cm–2 and upward. The apparent tilt angles were exceptionally high, above 45 degrees for all materials studied. In accordance with the trend described previously, the tetrasiloxane containing dimer showed a ferroelectric phase at high temperature. But in this case the columnar phase was found to be antiferroelectric. Hence, the general idea that trisiloxane cores promote antiferroelectricity and tetrasiloxanes promote the ferroelectric phase is still correct also for these materials in the SmC* phase, but not for the columnar phase. It can also be noted that the phase separation between siloxane, fluorinated tail and mesogenic parts of the molecules was so high that the material became columnar on lowering the temperature.

Optical second harmonic generation (SHG) was used to probe the response of a 200 nm thick electrically commanded alignment layer made of ferroelectric liquid crystal polymer (FLCP) film to an external DC electric field. The results show that for the field magnitudes in the range 0-2V/mu m the field induced reorientation effects represent only a relatively minor structural perturbation of the film. The switching process is monostable and shows characteristics of the "V-shaped'' switching. The response time of the SHG signal is relatively longer than what is measured for the bulk FLCP. Several mechanisms are considered as possible reasons for that.

Poly(vinylpyrrolidone) (PVP) has solubility properties that make it an attractive material for polymer-assisted synthesis applications; however, the naked polymer lacks reactive groups upon which to do chemistry. Furthermore, large differences in radical reactivity between 1-vinylpyrrolidin-2-one (NVP) and most other monomers lead to compositional drift during copolymerization, further complicating the introduction of functional groups into the polymer using this method. Monomers that are derivatives of NVP itself are expected to show smaller differences in radical reactivity and therefore provide a way of preparing PVP with adjustable properties. Three monomers introducing hydroxyl-functional groups and a new cross-linker, all derivatives of NVP, were synthesized and used in the preparation of a new type of hydrophilic polymer beads by aqueous suspension polymerization. These lightly cross-linked beads contain hydroxyl groups at a functional loading of 0.21-0.29 mmol/g and swell extensively in a broad range of solvents.

Antiferroelectric liquid crystals (AFLC) with 45° molecular tilt were stated to be the solution of the dark state problem in AFLC displays (AFLCDs). However, AFLCs that are available at present actually possess antiferroelectric (AF) to ferroelectric (F) transition of first order characterized by slow switching times which in turn deteriorates the dark state in AFLCDs. Here, we report on the switching behavior of a siloxane AFLC dimer with molecular tilt close to 45°. This material exhibits AF to F transition of second order at lower temperatures, something that enables display and fast switching of high contrast images in AFLCDs.

Polyvinylpyrrolidone (PVP) is a synthetic, nontoxic, water-soluble polymer commonly used in a wide range of applications including several pharmaceutical applications. One example of an important application is the controlled release and delivery of therapeutic agents into sites of inflammation or tumours. However, PVP lacks reactive groups, which limits the possibility of adding new functions to the polymer in order to modify its physical and chemical properties. Furthermore, large differences in radical reactivity between 1-vinylpyrrolidin-2-one (NVP) and most other monomers lead to compositional drift during copolymerization. This complicates the introduction of reactive groups into the polymer using this method. Monomers that are derivatives of NVP itself are expected to show smaller differences in radical reactivity and therefore provide a way of preparing PVP with adjustable properties. Here we present the synthesis of five NVP-based monomers and their use in the preparation of functional PVP with adjustable properties in terms of solubility, loading of functional groups, and molar mass. The results show the possibility of tailoring PVP for different biomedical applications e.g. drug delivery systems.[GRAPHICS]Copolymers from 1-vinylpyrrolidin-2-one.

The solubility properties of polyvinylpyrrolidone (PVP) make it an attractive material for several different polymer-assisted synthesis applications. However. PVP lacks reactive groups necessary for attaching compounds to the polymer. Furthermore, the radical reactivity of 1-vinylpyrrolidin-2-one (NVP) is different from most other monomers, which results in compositional drift during copolymerization. Therefore, introducing reactive groups into the polymer using this method is intricate. Smaller differences in radical reactivity are expected from monomers that are derivatives of NVP itself. Hence, such monomers provide a way of preparing PVP with adjustable properties. Four new monomers containing pendant double bonds, all derivatives of NVP, were synthesized and used in the preparation of a new type of hydrophilic polymer bead by aqueous Suspension polymerization. We also found that undec-10-en-l-ol can be used as a comonomer for the introduction of functional groups. The lightly crosslinked beads contain hydroxyl groups at a functional loading of 0.28 mmol/g and swell extensively in a broad range of solvents. Their potential as support materials has previously been demonstrated in a five-step solid-phase synthesis of 5-(2,4.6-trimethoxy-phenyl)cyclohexa-1,3-dienecarboxylic acid.

Polyvinylpyrrolidone (PVP) is a commonly used polymer with many different applications in the pharmaceutical, cosmetic and food industries. However, the lack of reactive groups and the difficulty in copolymerizing the monomer, N-vinylpyrrolidin-2-one (NVP) with most other monomers, limits the possibility of modifying the physical and chemical properties of the polymer. Monomers that are derivatives of NVP itself are expected to show small differences in radical reactivity as compared to the parent monomer and provide a way of adjusting the polymer properties without extensive compositional drift during copolymerization. Here we present the synthesis of two new functionalized NVP-based monomers and their copolymerization with alkylated NVP-monomers for the preparation of two functionalized PVPs with phase-selective solubility in heptane. Both copolymers showed 99.99% selective solubility in heptane over DMF (thermomorphic system) and 99.99% in heptane over 90% EtOH-H2O (latent biphasic system). These results suggest that the polymers could be used as soluble supports to facilitate recovery and recycling of catalysts or reagents from liquid/liquid systems after homogeneous reactions.

The scope of the present study is the response of a series of antiferroelectric dimeric or bimesogenic siloxanes to an applied electric field with focus on their pretransitional behaviour and the field-induced antiferro-ferroelectric (AF-F) transition. Most of these compounds possess a molecular tilt close to 45 degrees and spontaneous polarization in the field-induced ferroelectric (F) phase in the range of 250 - 300 nC cm(-2). In the dimers with a spacer length exceeding five carbons, a transformation from first to second order of the field-induced AF-F transition is found with temperature. Several different indications for this transformation are identified and their characteristics are discussed in the framework of the existing theoretical models. A large field-induced in-plane deviation of the sample optic axis was observed in the pretransitional region of several of the siloxane dimers and is likely due to the flexibility of the linking chains. The potential of the antiferroelectric bimesogenic siloxanes for displaying high contrast images and grey scale capability is shortly discussed. The large molecular tilt close to 45 degrees in combination with the field-induced AF-F transition of second order seems to be the most attractive features of these materials.

Electrically commanded surfaces (ECS) is a liquid crystal display concept whereby the switching of the alignment layer, which is driven by an electric field applied across the layer, is further transferred to the bulk liquid crystal material via elastic forces. This work presents the electro-optic response of a sandwich cell with alignment layer made of siloxane-based ferroelectric liquid crystal polymer, representing the ECS. The bulk liquid crystal material of choice was an in-house nematic mixture comprising fluorinated liquid crystalline compounds with negative dielectric anisotropy (Δε<0). We report a distinct linear electro-optic response, arising from the field-induced in-plane switching of the nematic which in turn is mediated by the ECS.

This work, performed by means of time-resolved high-resolution birefringence measurements, establishes the switching mechanism of electrically commanded surfaces (ECS) for liquid-crystal displays. A distinct polar electro-optic response, due to the field-induced in-plane switching of the molecules of the 200-nm ferroelectric liquid crystalline polysiloxane alignment layer representing ECS, was detected in a cell filled with isotropic liquid (hexadecane). The similarity between this response and the one reported recently in cells containing the same ECS but with a nematic liquid-crystal bulk with negative dielectric anisotropy (Δε<0) and field-free planar alignment provides direct and unambiguous proof that the switching in these cells is indeed mediated by the ECS.

Small quantities of the floppy bimesogen di(4PPB5)3Si were dissolved in an anticlinic liquid crystal consisting of a mixture of left-handed and right-handed TFMHPOBC, with enantiomer excess X=0.2 . The bimesogen dopant was found to promote anticlinic order with an anticlinic interaction coefficient per molecule udopant smaller than, but of the same order as, that of the rigid bent-core dopant P-7PIMB. For both dopants udopant was found to be much larger than that due to a pair of TFMHPOBC molecules in adjacent layers. The results are examined in terms of both the flexibility of the group linking the two legs of each dopant, as well as their chemical structure.

In this paper, we report the study of a new series of symmetric chiral liquid crystalline siloxane dimers, their related monomers, and two of those monomers with heptamethyltrisiloxane attached. All the dimers coupled with a trisiloxane show the SmCA phase, which in several cases has a large tilt angle greater than 40° over a wide temperature range, as well as high spontaneous polarisation in the field‐induced ferroelectric state. Spacer lengths of 3–6 and 11 carbons between the siloxane central unit and the mesogenic cores were used. Monomers with 3–6 carbons in the spacer showed only orthogonal phases while the monomer with an 11‐carbon spacer, as well as the monomers with siloxane attached, have a high tilt angle ferroelectric phase. The materials were characterized by means of DSC, NMR, X‐ray diffraction, electro‐optical methods (tilt angle and texture characterization) and polarization measurements.