In-situ photopolymerization of oriented liquid-crystalline acrylates

The scope of this thesis concerns a new method to produce oriented polymers by the in-situ photopolymerization of oriented liquid-crystalline acrylates. The desired macroscopic molecular order is already accomplished in the monomeric state prior to the polymerization. ... Zie: Summary

Synthesis and polymerization of liquid crystals containing vinyl and mercapto groups

Liquid-crystalline monomers containing two vinyl groups, two mercapto groups, or a 1:1 combination of the two have been synthesized and characterized in terms of their mesomorphic properties. These monomers can be photopolymerized in situ in an appropriate ratio of vinyl and mercapto groups to form highly ordered liquid-crystalline main-chain polymers. During polymerization in the nematic phase the appearance changes from clear in the highly aligned birefringent state to opaque. This effect is probably due to scattering which is caused by the disturbance of the macro alignment as a result of the polymerization shrinkage and/or phase separation. In some cases, the reaction mixtures pass from the nematic to the crystalline state which results in a reduction in the degree of conversion and also in a change in the microcrystalline state. Crystallization can be suppressed by promoting asymmetry of the molecular structure which leads to a higher degree of conversion

Synthesis and polymerization of liquid crystals containing vinyl and mercapto groups. Liebigs

. Synthesis and polymerization of liquid crystals containing vinyl and mercapto groups. Liebigs Annalen : Organic and Bioorganic Chemistry, 1997(11) Please check the document version of this publication: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: www.tue.nl/taverne Take down policy If you believe that this document breaches copyright please contact us at: [email protected] providing details and we will investigate your claim. Keywords: Photopolymerization I Liquid crystals I Main-chain polymers I Thiol-ene chemistry Liquid-crystalline monomers containing two vinyl groups, two mercapto groups, or a 1:l combination of the two have been synthesized and characterized in terms of their mesomorphic properties. These monomers can be photopolymerized in situ in an appropriate ratio of vinyl and mercapto groups to form highly ordered liquid-crystalline main-chain polymers. During polymerization in the nematic phase the appearance changes from clear in the highly aligned birefringent state to opaque. This effect is probably due to scattering which is caused by the disturbance of the macro alignment as a result of the polymerization shrinkage and/or phase separation. In some cases, the reaction mixtures pass from the nematic to the crystalline state which results in a reduction in the degree of conversion and also in a change in the microcrystalline state. Crystallization can be suppressed by promoting asymmetry of the molecular structure which leads to a higher degree of conversion

Self-sustained actuation from heat dissipation in liquid crystal polymer networks

Liquid crystal polymer networks (LCNs) lead the research geared toward macroscopic motion of materials. These actuators are molecularly programed to adapt their shape in response to external stimuli. Non-photo-responsive thin films of LCNs covered with heat absorbers (e.g., graphene or ink) are shown to continuously oscillate when exposed to light. The motion is governed by the heat dissipated at the film surface and the anisotropic thermal deformation of the network. The influence of the LC molecular alignment, the film thickness, and the LC matrix on the macroscopic motion is analyzed to probe the limits of the system. The insights gained from these experiments provide not only guidelines to create actuators by photo-thermal or pure photo-effects but also a simple method to generate mechanical oscillators for soft robotics and automated systems

High-contrast thin-film polarizers by photo-crosslinking of smectic guest-host systems

\u3cp\u3eThe preparation of high-contrast thin-film polarizers by photo-crosslinking of smectic guest-hosts systems for use in liquid crystal displays (LCDs) is presented. Thin-film polarizers has the advantages of significant reduction in display and weight, and the positioning of the polarizers inside the cell eliminates all parallax-related issues and is beneficial to the robustness of the display. One possible approach to obtaining thin, coatable polarizers based on the use of lyotropic liquid-crystalline dyes that form a crystalline polarizer with sub-micrometer film thickness after coating and evaporation of the solvent. The low viscosity of the reactive liquid crystals facilitates easy alignment, while the in setu photopolymerization provides freedom in choosing the photopolymerization temperature and conditions enabling the selection of the optimum phase and molecular order. This thin-film technology could be an alternative to traditional sheet polarizers in LCD.\u3c/p\u3

Four-Dimensional Printed Liquid Crystalline Elastomer Actuators with Fast Photoinduced Mechanical Response toward Light-Driven Robotic Functions

Remote light exposure of photoresponsive liquid crystalline polymers has drawn great attention over the last years as an attractive strategy to generate mechanical work with high spatial resolution. To tailor these materials into practical engineering devices, it is of key importance to gain control over their morphology and thus precisely program their mechanical response, which must also be fast and relevant in magnitude. In this communication, we report the four-dimensional (4D) printing of azobenzene-containing liquid crystalline elastomers (LCEs) that respond to light. During extrusion of the LCE precursor, mesogen orientation is defined by the needle’s moving direction enabling a precise definition of the director, which is later fixed by photopolymerization. Fast mechanical responses have been observed in these 4D printed LCE elements when excited with ultraviolet (UV) light. These 4D printed elements lift objects many times heavier than their own weight, demonstrating a capacity to produce effective work. Photochemical and photothermal contributions to the deformation and force have been identified. Advantageously, the use of blue and UV light excitation enables adjustment of generated forces that can be maintained even in the dark and can be released by light excitation or temperature. The demonstrated ability to generate light-responsive elements quickly delivering sufficient work paves the way for implementing remotely addressed mechanical functions to future soft robotics and engineering