An High Sensitivity Optical Sensor For Chloroform Vapours Detection Based On Nanometric Film of δ-Form Syndiotactic Polystyrene

A film of syndiotactic polystyrene (sPS) in the nanoporous cryst. d form was used for the detection of chloroform in the vapor phase at very low concn. The variation of the refractive index due to the chloroform sorption within the polymer was used as transduction property. Reflectivity measurements by a fiber optic refractometer, coated with a nanometric (73 nm) film was performed at very low pressure of chloroform (between 0.2 and 5 torr) at three different temps. (35, 49 and 56°). Mass sorption expts. were concurrently performed with an electronic microbalance operating in the same conditions of the optical sensor. Major result from the gravimetric tests is that the analyte is mainly adsorbed into the nanoporous phase where the penetrant mols. can be hosted with a certain selectivity based on both size exclusion and host guest interactions. The quant. correlation between the mass of analyte sorbed within the polymer layer and the refractive index variation is temp. independent. A phenomenol. equation based on the Lorentz-Lorenz law is proposed to describe the effect of the chloroform uptake including both concn. and polarizability changes on the refractive index of the sensible layer.