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Liquid crystal elastomers

Marta Žebovec (2011) Liquid crystal elastomers. Diploma thesis.

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    The graduation work presents liquid crystal elastomers (LCE), which are made from liqid crystals and elastomers. Their main microscopic properties are orientation, positional order and the smectic order to the layer normal. We see these properties as different phase of the same matter. We can find them not only in crystal and liquid phase but in phases between those: in liquid crystal phases. Liquid crystal may flow, drip and they take a shape like a liquid, but they are similar to crystals because its molecules may be oriented in a crystal-like way. Elastomers are made from polymeric chains, which form an elastomeric net. That gives them macroscopic properties like shape and deformation. If we act with force on them they stretch in the direction in which they are being pulled. When a deforming force is removed, they resume their original shape, if the force is not too strong. LCE have properties of both. Their very interesting property is thermomechanical response. The liquid crystals in them go with heating from nematic phase into izotropic phase. LCE are in the direction of director in nematic phase longer than in isotropic. We explored how the crosslinking density affect the isotopic to smectic A phase transition. We used two samples with different crosslinking density. Both samples exhibit first order I-SmA phase transitions. By changing the crosslinking density the anomaly of heat capacity and with that thermomechanical response is widened. We made a mechanical model, which we can use at school, with intention to introduce children what are LCE and their thermomechanical response.

    Item Type: Thesis (Diploma thesis)
    Additional Information: Ferbarjeva nagrada za študijsko leto 2011
    Keywords: liquid crystals, elastomers, liquid crystal elastomers, thermomechanical response, phase transition, critical point, latent heat
    Number of Pages: 62
    Language of Content: Slovenian
    Mentor / Comentors:
    Mentor / ComentorsIDFunction
    red. prof. dr. Mojca ČepičMentor
    prof. dr. Zdravko KutnjakComentor
    Link to COBISS: http://www.cobiss.si/scripts/cobiss?command=search&base=50126&select=(ID=8954441)
    Institution: University of Ljubljana
    Department: Faculty of Education
    Item ID: 397
    Date Deposited: 21 Oct 2011 07:44
    Last Modified: 20 Dec 2011 07:45
    URI: http://pefprints.pef.uni-lj.si/id/eprint/397

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