CHOLESTERIC LIQUID CRYSTALS MICRODROPLETS DISPERSED IN POLYMERIC FILMS SENSITIVE TO TEMPERATURE AND MECHANICAL STIMULI

• Autor(a) principal: Bracco, Annalisa
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/160626
• topic: Cholesteric liquid crystals; cholesteryl oleyl carbonate; 4-cyano-4’-pentylbiphenyl; cellulose-based films; polydimethylsiloxane films; polyurethane films; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

The deterioration of civil engineering constructions (buildings, bridges, dams, etc.) may have catastrophic consequences and may cause their collapse. The absence of a prior signal when a civil construction is degrading has already caused hundreds of deaths. An example is the disaster that occurred in the northwest of Italy in Genoa when the Morandi bridge collapsed. The collapses be a consequence of the excess of structural strength, the result of natural phenomena like earthquakes, or the absence of infrastructure maintenance. Temperature and humidity also affect the behavior of materials leading to structural deformation in existing constructions. A solution to this problem could be a monitoring sensor that, when applied to the structure wall and under structural deformations or temperature variations, would change the color of the reflected light in the visible range. Cholesteric liquid crystals microdroplets dispersed in a polymeric and elastomeric film could be used as a sensor to study the structural alteration. The elastomeric matrix presents high elastic deformations and encapsulating the cholesteric liquid crystals (CLCs) microdroplets exhibits the optical properties of the liquid crystals. The class of elastomers/polymers used to fabricate this sensor are Polyurethane, Polydimethylsiloxane (PDMS), Cellulose Acetate (CA), and Acetoxy propyl cellulose (APC). The cholesteric liquid crystals are prepared by mixing the cholesteryl oleyl carbonate (COC) as a chiral molecule, and the 4-cyano-4’-pentylbiphenyl (5CB), as a nematic liquid crystal. Polymeric films were successfully produced with the incorporation of cholesteric liquid crystals microdroplets. These films showed the ability of changing color with the variations of temperature.