Chiral Composite Networks for Sensing Volatile Organic Compounds Towards Liquid Crystal Nose (LC-nose).

Composite chiral networks were prepared by co- polymerization of cholesteric siloxane monomers with low molar mass monomers bearing hydrogen bonding, polar and non-polar side groups ( acrylic acid, vinylpyridine, benzyl acrylate, and aliphatic acids ). Polymerization was conducted between two plastic plates at elevated temperatures when compounds formed chiral liquid crystalline state. After polymerization thin polymer films were formed, the upper plastic film was peeled off and the surface of polymer composite was exposed to a particular VOC. The response of polymer films to VOCs (spectral shift of the selective reflection band) was studied by spectroscopic methods and morphological surface changes were studied by atomic force microscopy (AFM). It was shown that by varying the composition of materials it is possible to change their sensitivity to polar and non-polar VOCs. The mechanism of this sensitivity was also studied by modeling both gas diffusion inside the polymer and polymer optical properties. The selectivity of the whole system can be further improved by comparing relative spectral and color changes of a few polymer films simultaneously. Thus, the prototype of LC-nose based on polymer networks could be created.