Cholesteric Liquid Crystal Based Polymeric Sensors for Detection of Volatile Organic Compounds


Batır Ö., Bat E., Büküşoğlu E.

Eastern Mediterranean Chemical Engineering Conferences 9, Ankara, Turkey, 30 August - 01 September 2018, pp.1

  • Publication Type: Conference Paper / Summary Text
  • City: Ankara
  • Country: Turkey
  • Page Numbers: pp.1
  • Middle East Technical University Affiliated: Yes

Abstract

Polymeric materials have gained a recent interest especially in sensor technology. Optical properties of polymeric sensors can be tuned by templating the polymer network by liquid crystals (LCs).[1] LCs are stable fluid phases that possess molecular ordering. When a chiral dopant is added, helical twisting of the molecular directional order (n) can be induced leading to a cholesteric liquid crystalline (CLC) phase.[2] CLCs exhibit a wavelength and polarization selective reflection due to their periodic helical structure. The periodic helical structure, therefore the wavelength of the reflected light, has been shown to be influenced by various external stimuli, such as temperature, electricity and chemicals.[3] Therefore, the presence of the chemical vapors can be identified according to extend of the change in the color appearance of the polymeric films templated from CLCs. In this study, CLC-templated polymeric films were fabricated in the presence of strain orthogonal to the molecular director and tested for sensor applications in a controlled experimental system where the concentration of the volatile organic compound (VOC) is controlled. Upon exposure to VOC vapor, we observed a color change that is influenced by the amount of strain on the cholesteric axis of the polymeric sensor.

Polymeric materials have gained a recent interest especially in sensor technology. Optical properties of polymeric sensors can be tuned by templating the polymer network by liquid crystals (LCs).[1] LCs are stable fluid phases that possess molecular ordering. When a chiral dopant is added, helical twisting of the molecular directional order (n) can be induced leading to a cholesteric liquid crystalline (CLC) phase.[2] CLCs exhibit a wavelength and polarization selective reflection due to their periodic helical structure. The periodic helical structure, therefore the wavelength of the reflected light, has been shown to be influenced by various external stimuli, such as temperature, electricity and chemicals.[3] Therefore, the presence of the chemical vapors can be identified according to extend of the change in the color appearance of the polymeric films templated from CLCs. In this study, CLC-templated polymeric films were fabricated in the presence of strain orthogonal to the molecular director and tested for sensor applications in a controlled experimental system where the concentration of the volatile organic compound (VOC) is controlled. Upon exposure to VOC vapor, we observed a color change that is influenced by the amount of strain on the cholesteric axis of the polymeric sensor.