Polymer-BaTiO _3 composites: Dielectric constant and vapor sensing properties in chemocapacitor applications

摘要

In this work, composite materials, prepared by inclusion of various amounts of BaTiO _3 nanoparticles in PBMA and PHEMA polymer matrices, were characterized in respect to their dielectric properties and then used as the sensing layer of capacitive-type sensors. BaTiO _3 was found to be less effective in enhancing the permittivity of PHEMA, as compared to PBMA, in the range of 1 kHz-1 MHz, possibly due to the observed lower quality of dispersion in the polymer matrix and the higher polarity of the polymer in the former case. The response of the composite-based chemocapacitors to four vapor analytes, covering a wide range of dielectric constants, was studied in relation to the BaTiO _3 load. In all cases, with increasing amount of BaTiO _3 load, the absolute value of capacitance response was increased, due to the corresponding increase of the initial capacitance of the sensing composite layer. However, the corresponding normalized (to the initial capacitance of the sensing composite layer) capacitance values were reduced, due to the decreased volume fraction of the sorbing polymer material in the composite matrix. An exception to this trend, observed upon exposure of the PBMA/BaTiO _3 chemocapacitors to low humidity levels, is also presented and discussed.