Sulfur dioxide (SO 2 ) belongs to the six major pollutants of atmospheric air [1] and ranks first in the mass of exhausts to the atmosphere. Therefore, studies on the development of methods for determining SO 2 in atmospheric air [2], including those with the use of optical chemical sensors (OCS) [3,4,5] are of high current importance.Among the sensing materials of SO 2 sensors are polycrystalline films [2], polymers with physically bound analytical reagents [4], and Langmuir-Blodgett layers [5]. Complexation reaction between SO 2 molecules and amino groups in molecules of analytical reagents is most often used as an analytical reaction. This reaction is well-known and often used for the extraction of SO 2 from waste gases [6]. In the previously developed optode [4], plasticized PVC films to which molecules of aromatic aldehydes, phenoxazine derivative as the main chromoionophore, and lipophilic alcohols were physically bound were studied as sensing materials. The reversible reaction of the bisulfite anion with aromatic aldehyde molecules followed by the detection of with an acid-base indicator was HSO 3 -HSO 3 -used as the working reaction. Analysis was performed using samples with specially controlled moisture content. The refractometric sensor based on LangmuirBlodgett layers exhibited linear calibration characteristics only in the range of rather high concentrations (500-1500 mg/m 3 ) [5].In recent years, particularly because of the rapid progress of biosensors, it has become evident that the most promising sensing materials are those in which molecules of analytical reagents or basic fragments of such molecules are chemically bound to matrix materials by covalent of ionic bonds. From the viewpoint of the stability of sensor characteristics and therefore, the practical application of OCSs, functional polymers undoubtedly offer most promise among the polymeric materials [7]. In these polymers, fragments of analytical reagents are chemically (via covalent or ionic bonds) bound to the polymer chain. In addition to the thermodynamic stability of sensing materials and the stability of sensor characteristics in time, functional polymers exhibit one more merit. This merit is the possibility of purposeful molecular design (synthesis) of materials with the specified gas-adsorption and sensing properties. It should also be noted that all the aforesaid ARTICLES Abstract-The effects of the chemical and phase composition of acrylonitrile and alkyl methacrylate (Alkyl-MA) copolymers with styrene sulfonates (SS) of triphenylmethane dye cations on the gas permeability and sensing properties of their films were studied for developing an optical chemical sensor (OCS) for sulfur dioxide (SO 2 ) on the basis of functional polymers. Of the three triphenylmethane dyes tested, namely, fuchsine, Crystal Violet, and Brilliant Green (BG), only the last dye was selected for molecular design. It was shown that the copolymer of Decyl-MA with SS-BG with the degree of modification DM = 0.10 is the best material among the studied ones from ...
In our previous paper [1], we presented the results of studying the effect of SO 2 on the electronic absorption spectra of thin films fabricated of functional polymers from two classes. These polymers were copolymers of acrylonitrile ad alkyl methacrylates with styrene sulfonates of triphenylmethane dyes, in particular, Brilliant Green (BG). It was shown that the studied functional polymers possess insufficiently high gas-adsorption and sensing properties for being used as sensing layers in optical chemical sensors (OCSs) for controlling SO 2 in the air of the working area.While searching for materials with better sensing properties, we studied the effect of the concentration of SO 2 on the absorption spectra of films of ionogenic aromatic polyamides, methyl methacrylate copolymers (PMMA), and functionalized poly(dimethylsiloxanes) (PDMSs) differing in chemical structure and the degree of modification (DM) and bearing ionically bound Brilliant Green (BG) cations.First, we studied the effect of SO 2 on the electronic absorption spectra of films in vacuum and compared the sensitivities of the studied functional polymers with those of the previously studied polymers [1]. Next, for films of ionogenic PDMSs of different thicknesses, we obtained calibration functions in a wide range of SO 2 concentrations in an air flow. EXPERIMENTAL Materials.Aromatic polyamides bearing sodium sulfonate groups were of an average molecular mass of (1.5-2.0) × 10 4 . Exchange reactions between aromatic polyamides and BG oxalate were conducted in polar solvents (DMFA and dimethyl sulfoxide, DMSO). For this purpose, a stoichiometric amount of a solid dye was added to a polyamide solution (PA-1 in DMSO, PA-2 or PA-3 in DMFA) at 60 ° C while intensely stirring. The reaction mixture was stirred for 1 h; next, polymers were precipitated with isopropanol, separated from the solution on a filter, washed with a 5 : 1 isopropanol-water mixture and with pure isopropanol, and dried at room temperature under vacuum. For these and the other polymers used in this work, the degree of substitution of alkali metal cations with BG cations (degree of modification, DM) was estimated from the data of flame photometry. The copolymer of methyl methacrylate immobilized with BG cations was obtained by ion exchange from a copolymer of potassium methacrylate with methyl methacrylate. The reaction was conducted in a methanol-DMSO mixture at 50 ° C using the stoichiometric ratio of BG to potassium methacrylate links in the copolymer. The time of reaction was 1 h. After the reaction was completed, the copolymer was precipitated with water, and washed and reprecipitated from a DMSO solution. A modified copolymer of dimethyland methyl-( γ -hydroxypropyl)siloxane containing ARTICLES Abstract -The search for functional polymers for an optical chemical sensor (OCS) for sulfur dioxide was continued. Copolymers of polyamides, methyl methacrylate (PMMA), and poly(dimethylsiloxanes) (PDMSs) were examined. It was shown that the sensitivity of the spectral parameters of polymer...
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