RU2537387C2 - Method of determining element composition of polymers and oligomers based on 3,3-bis(azidomethyl) oxetane (bamo) by method of ir-spectroscopy - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to physical-chemical analysis and can be used in determination of element composition of polymers and oligomers based on 3,3-bis(azidomethyl) oxetane (BAMO) by method of IR-spectroscopy. Method of determining element composition of polymers and oligomers based on 3,3-bis(azidomethyl) oxetane (BAMO) consists in the following: determination of element composition of BAMO-based oligomers is carried out by optic densities of bands of absorption of IR-spectrum of samples in form of film, prepared from oligomer melt or its solution in dimethylformamide, in region 400-4000 cm^-1, which conditions content of nitrogen, carbon, hydrogen, oxygen and chlorine in analysed samples. Determination is carried out by intensity of bands of absorption of N₃-group, CCl-groups with respect to optic densities of CH₂- or C-O-C-groups, with nitrogen being determined by graph showing dependence of the value of ratio of N₃ band optic density to band COC optic density on content of nitrogen in oligomer, carbon is determined by graph of dependence of the value of ratio of N₃ band optic density to band COC optic density on content of nitrogen and carbon, hydrogen carbon is determined by graph of dependence of the value of ratio of N₃ band optic density to band CH₂ optic density on ratio of nitrogen and hydrogen content, oxygen is determined by graph of dependence of the value of ratio of N₃ band optic density to COC band optic density on ratio of nitrogen and oxygen content, chlorine is determined by graph of dependence of the value of ratio of CCl band optic density to CH₂ band optic density on residual chlorine content.

EFFECT: extension of assortment of determined groups.

7 dwg, 1 tbl

Description

The invention relates to physicochemical analysis and can be used to determine the elemental composition of azide-containing oligomers by IR spectroscopy.

The task of quantitative organic elementary analysis is to determine the non-functional groups of oligomers, and the content of the individual elements that make up the organic matter.

The principle of analysis, proposed a hundred years ago by Liebig and has not undergone significant changes to date, is the destruction of organic matter by burning, followed by quantitative capture of combustion products [1]. As for the analysis technique, it has now achieved significant success. Undoubtedly, the most significant achievement was the development of a microanalytical method, in which only a few milligrams of a substance is required to conduct a quantitative elemental analysis [2].

Determination of carbon and hydrogen. The classic method of microanalytical determination of carbon and hydrogen is the Pregl method [3]. According to this method, vapors of the substance are oxidized, passing them in a mixture with oxygen through a layer of copper oxide and lead chromate heated to 750 ° C, placed in a burning tube. Carbon dioxide and water are trapped in absorption devices and are determined by weight gain. The oxidation products of other elements are retained by absorbers (silver and lead dioxide) located in the tube for burning. Catalytic combustion is less common; in this case, instead of copper oxide and lead chromate, a platinum contact is in the combustion tube and oxidation occurs only due to gaseous oxygen.

A new high-speed method of microanalytical determination of carbon and hydrogen was developed in recent years at the Institute of Organic Chemistry of the USSR Academy of Sciences (M.O. Korshun, V. A. Klimova) [4]. According to this method, a sample of a substance is subjected to rapid thermal decomposition (in a special glass) with a lack of oxygen; pyrolysis products (when leaving the cup) in the presence of an excess of oxygen are oxidized almost completely to H ₂ O and CO ₂ . The final oxidation of the pyrolysis products occurs when they pass in a mixture with a large excess of oxygen through the zone of an empty combustion tube heated to 850–950 ° C. The oxygen transmission rate in this method reaches 35-50 ml per minute, i.e. 10 times the oxygen transmission rate with previous microanalytical methods. The use of this method makes it possible to burn a sample of organic matter for 10-15 minutes (with conventional microanalytical methods, the burning time is 30-45 minutes).

The carbon and hydrogen content can be determined even faster if, instead of trapping and weighing the compounds, the amount of CO ₂ and H ₂ O is determined from the vapor pressure. Such a method, however, requires more sophisticated equipment.

If other elements are present in the organic matter, in addition to carbon, hydrogen and oxygen, the volatile products of their oxidation are captured outside the combustion tube in special apparatuses, and these oxidation products, therefore, do not interfere with the quantitative determination of carbon and hydrogen in the form of carbon dioxide and water. This principle of operation makes it possible simultaneously with carbon and hydrogen to determine other elements (non-volatile combustion products are determined by weighing the residue).

Determination of halides and sulfur [5]. When analyzing organic substances containing halogen and sulfur, the general principle of the method is mainly preserved - burning in a tube not filled with oxidizing agent; halogen or sulfur are absorbed in a special apparatus filled with metallic silver. At 450 ° C, metallic silver quantitatively absorbs chlorine, bromine, and iodine, and at 500–750 ° C, sulfur oxides. Silver is placed in front of the absorption apparatus for carbon dioxide and water. Thus, carbon, hydrogen and halogens or carbon, hydrogen and sulfur are simultaneously determined. For microanalytical determination of halides, one of the following methods can also be used:

1. Hydrogenation of a halogen-containing organic substance in the presence of a nickel catalyst. The amount of hydrohalic acid formed in this case is usually determined by the volumetric method.

2. The decomposition of organic matter by metallic sodium, calcium or lithium in appropriate solvents (alcohols, ethanolamine, dioxane, etc.). The halide salts formed in this process are identified by one of the inorganic analysis methods.

Determination of nitrogen [6]. Microanalytical determination of nitrogen is carried out according to the methods of Dumas and Kjeldahl. According to the Dumas method, an organic substance containing nitrogen is burned due to oxygen heated by copper oxide in a tube filled with carbon dioxide. In this case, carbon is oxidized to carbon dioxide, hydrogen to water, and all nitrogen contained in the substance is released in the form of elemental nitrogen, which is quantitatively displaced by carbon dioxide into a nitrogen meter with a solution of caustic potassium. Carbon dioxide is absorbed by alkali, and nitrogen gas is collected in the upper, graduated part of the nitrogen meter (usually with a capacity of 2 ml and graduated to 0.01 ml), where its volume is measured. After bringing the resulting gas volume to normal conditions, the percentage of nitrogen in the substance is calculated.

According to the Kjeldahl method, a nitrogen-containing substance is destroyed by concentrated sulfuric acid (in a Kjeldahl flask) in the presence of various catalysts (PtCl ₄ , PdCl ₂ , CuO, HgO, Se, etc.), and ammonium sulfate is formed. The latter, under the action of alkali, releases free ammonia, which is distilled off with steam and titrated with acid.

Determination of oxygen [6]. The determination of oxygen is usually carried out indirectly, if after determining the percentage in the substance of all the elements found, the amount differs from 100%, then the difference is the percentage of oxygen. The only method for the direct determination of oxygen in organic substances, which can be considered reliable, is to restore the products of thermal decomposition of the substance by charcoal in a stream of nitrogen. According to this method, the substance is decomposed in a stream of nitrogen (previously thoroughly purified from oxygen impurities) in a quartz tube. Decomposition products pass through a layer of granular soot heated to 1150 ° C. In this case, oxygen quantitatively passes into carbon monoxide, which, passing through a heated layer of iodine pentoxide or copper oxide, is quantitatively oxidized to carbon dioxide.

If organic matter, in addition to carbon, hydrogen, oxygen and nitrogen, also contains other elements, then they can be determined after preliminary oxidation of the substance by heating with fuming nitric acid (Carius burning). In this case, halogens are determined in the form of silver halides, sulfur in the form of barium sulfate, phosphorus in the form of magnesium pyrophosphate. The metals contained in a substance can also be determined by conventional inorganic chemistry methods.

Definition of halogens. To determine halogens, the flask method, called the Schoeniger method and the reduction (ammonia) method, are widely used [3, 5, 6].

- Determination of chlorine and bromine (flask method). Recently, the flask method, also called the Schoeniger method, is widely used to determine halogens. This decomposition method is so simple that it is widely recognized. The flask method consists in decomposing a substance by burning a sample wrapped in filter paper and placed in a platinum mesh or spiral located in the center of the flask filled with oxygen. Combustion products are absorbed by alkali, and the resulting halides are determined by mercury titration with diphenylcarbazone as an indicator.

- Determination of halogens by the reduction (ammonia) method. The method is based on the decomposition of an organic compound in an atmosphere of gaseous ammonia in a quartz tube at 700-750 ° C. Ammonia from the cylinder through the fine adjustment valve enters the quartz tube.

- Photometric determination of chlorine. The method is based on the mineralization of the oligomer in a flask with oxygen and the subsequent nephelometric determination of chlorine by reaction with silver nitrate in a nitric acid medium. The sensitivity of the method is 0.01 mg in 25 ml of photometric solution.

A known method [7] for determining the content of free OH groups in oligoxetanediols using the method of IR spectroscopy. The technique is based on determining the dependence of the ratio of the optical densities of the absorption band of free OH groups at υ = 3617 cm ^-1 and the optical density of the absorption band of OH groups associated with intermolecular hydrogen bonds at υ = 3348 cm ^-1 . The technique is designed to determine the content of free groups in oxetanediols and is not suitable for determining the elemental composition of oligomers based on 3,3-bis (azidomethyl) oxetane (BAMO). This technique is designed to determine the content of hydroxyl groups in samples.

When determining the content of free OH-groups, the band bend is used at υ = 3617 cm ^-1 , which is caused by the wide complex shape of the absorption band of OH-groups. In this case, a number of absorption bands are superimposed due to both free absorption bands and coupled inter- and intramolecular bonds.

Since the absorption band of OH groups at υ = 3348 cm ^{-1 was} chosen as the reference absorption band, it should be noted that the optical density of this band strongly depends on the molecular structure of the electron acceptor O-H + and the electron donor OR-, which form Н complexes of the form O- N ... O ... R. One of the main criteria for the existence of an H-bond is a shift in the frequency Δυ of the absorption band due to intermolecular bonds and a change in the optical density of this band.

Therefore, the use of the absorption band of intermolecular bonds of OH groups at υ = 3348 cm ^-1 will cause strong fluctuations in the ratio of the optical densities of the absorption bands of free OH groups and OH groups connected by intermolecular bonds. In this case, a significant increase in the relative error in determining the content of functional groups — free OH groups — is possible.

The closest technical solution is the method for determining the elemental (CHN) analysis by the automatic method [2]. The principle of operation of CHN analyzers is that a sample of organic matter undergoes oxidative decomposition in a reactor. This decomposition begins at the location of the sample and ends in a special oxidation zone. Then, the gaseous decomposition products pass through the reduction zone, where the excess of oxygen introduced into the reactor or separated by reagents is absorbed, and nitrogen oxides are reduced to elemental nitrogen. In order to separate a gas mixture, gas chromatography, selective adsorption, or a combination thereof are usually used. The content of oxidation products is measured using a thermoconductometric detector (katharometer).

The disadvantage of this method is the complexity, high cost of the equipment, since a second reactor is needed to restore the decay products, the need to use additional detectors for oxygen and chlorine determination, and high weighing accuracy (usually up to 0.001 mg). In addition, oxygen and helium are required to be supplied in a very high degree of purity (99.99%) as a reagent gas for oxidation in sufficiently large quantities (2-5 L per analysis).

The aim of the present invention is to simplify elemental analysis, increase its expressivity and the simultaneous determination of nitrogen, hydrogen, carbon, oxygen, chlorine.

For this, it is proposed to use only one device - an IR spectrometer, which is a widespread and universal device. This goal is achieved by the fact that in the method for determining the elemental composition of oligomers based on 3,3-bis (azidomethyl) oxetane (BAMO) by IR spectroscopy, the samples were removed as films on a KBr substrate in the range of 4000-400 cm ^-1 .

The nitrogen content was determined by taking the IR spectra in a liquid cuvette from CaF ₂ with a thickness of 0.067 mm, chlorine in a liquid cuvette from KBr with a thickness of 0.02 mm in the region of 2200-700 cm ^-1 . In this case, nitrogen was determined from the graph of the dependence of the optical density of the N ₃ (D ₂₁₀₀ ) band on the nitrogen content in the oligomer; chlorine - according to the graph of the optical density of the absorption band of C-Cl at υ = 740 cm ^-1 on the chlorine content.

The developed method allows to obtain the complete elemental composition (C, H, N, O, Cl) from the IR spectra of the sample. The method of IR spectroscopy was chosen due to its wide capabilities in identifying structural fragments of molecules and establishing elemental composition from them.

As the studied samples, 3,3-bis (azidomethyl) oxetane (o-BAMO) and oligomers based on it (co-oligomer BAMO and glycidyl azide (oligo-BHA), co-oligomer BAMO and tetrahydrofuran (oligo-BAMT), etc.) were analyzed (see . table).

When determining elemental analysis, the IR spectra of the samples were recorded as films on a KBr substrate. The film was prepared in the form of a melt or solution in dimethylformamide (DMF), dried in an oven until characteristic solvent bands disappeared. The choice of DMF is due to the fact that it is an effective solvent and weakly absorbs in the absorption region of the azide and C-Cl groups. Based on the processing of the basic spectra, a calibration graph was constructed for the ratio of the ratio of the optical density of the azide band N ₃ to the optical density of the С-О-С band (D ₂₁₀₀ / D ₁₁₀₀ ) versus the nitrogen oligomer content determined by elemental analysis. In this case, a linear relationship with a correlation coefficient of R ² = 0.99 (Fig. 1) is obtained. Using the obtained dependence, it is possible to determine the nitrogen content in the oligomer.

Then, the dependence of the ratio of the optical density of the N ₃ band to the C-O-C band (D ₂₁₀₀ / D ₁₁₀₀ ) on the ratio of the nitrogen and carbon content in the oligomer was constructed (FIG. 2); the dependence of the ratio of the optical density of the strip N ₃ to the band of CH ₂ (D ₂₁₀₀ / D ₂₉₀₀ ) on the ratio of the nitrogen and hydrogen content in the oligomer (figure 3); the dependence of the ratio of the optical density of the strip N ₃ to the optical density of the strip С-О-С (D ₂₁₀₀ / D ₁₁₀₀ ) on the ratio of the nitrogen and oxygen contents (Fig. 4). For calibration, samples were used whose elemental composition (C, H, N) was determined on a 2400 series PerkinElmer elemental analyzer, chlorine according to the Schoeninger method, oxygen minus 100%.

The presence of hydrogen atoms in the structure is mainly due to CH ₂ groups; therefore, knowing the nitrogen content in the sample from the ratio of the optical density of the azide band to the CH ₂ band, one can determine the hydrogen content.

Based on the structure of the samples under study, it is evident that the oxygen content is due to the presence of C — O — C groups, which allows us to use graphs for the dependence of the ratio of the optical densities of the azide and C — O — C groups on the ratios of nitrogen and oxygen contents for oxygen. Given the linearity of the obtained dependencies, it is also possible to determine the oxygen content in the oligomers at a predetermined nitrogen content.

Thus, knowing the nitrogen content determined by the schedule (figure 1), and using the graphs (figure 2-4), you can determine the content of carbon, hydrogen and oxygen.

Since chlorine in the oligomers is in the form of a C-Cl group, this circumstance can be used to determine the chlorine content in the sample by the intensity of the C-Cl band. The determination of chlorine in oligomers was determined by the same IR spectrum as the optical density of the analytical absorption band at υ = 740 cm ^-1 with respect to the band of CH ₂ groups at υ = 2900 cm ^-1 . As the base band, we chose the CH ₂ band, since it has the greatest stability. In this case, a linear relationship with a correlation coefficient R ² = 0.92 was obtained (Fig. 5).

It is also possible to take spectra in a liquid cuvette in the region of 2200-700 cm ^-1 . We used a liquid cuvette from CaF ₂ with a thickness of 0.067 mm, the sample was prepared in the form of a solution in DMF at a ratio of 0.075 g oligo-BAMO per 10 cm ³ DMF to determine elemental analysis and a cuvette with a thickness of 0.02 mm from KBr with a sample concentration of 0.2 g per 1 cm ³ DMF to determine the residual chlorine.

The correlation coefficient obtained when using a liquid cuvette is slightly higher (see Fig. 6, 7) than when taking a sample in a film, since in the case of using a liquid cuvette, only the azide group and the C-Cl group are analyzed, and the obtained linear dependence allows determination of nitrogen and residual chlorine in oligomers.

Determination of nitrogen and chlorine using a liquid cuvette gives a more accurate result, but it is more laborious in comparison with the use of a film on a KBr substrate and is not applicable for samples with a high molecular weight (> 20,000 g / mol) due to their poor solubility in DMF.

Thus, we have developed an effective, fairly simple and rapid method for determining the elemental composition of BAMO-based oligomers, which reduces the analysis time by three. Due to its wide distribution and availability, the IR spectrometry method can be used in almost any laboratory. The information obtained allows us to draw the correct conclusion about the elemental composition of oligomer samples.

Also, the proposed method allows you to simultaneously determine nitrogen, hydrogen, carbon, oxygen, chlorine. The advantage of the proposed method is that there is no need to use scarce and expensive reagents, weighing with high accuracy, as well as working with gases, the simplicity and expressness of the method.

The results of the comparison of the two analysis methods are presented in the table.

Information sources

1. Pryanishnikov ND Workshop on Organic Chemistry. - M.: State scientific and technical publishing house of chemical literature, 1956. - 244 p.

2. Gelman N.E. Methods of quantitative organic elemental microanalysis. - M.: Chemistry, 1987 .-- 296 p.

3. Klimova V.A. The main micromethods for the analysis of organic compounds. 2 ed., Ext. - M .: Chemistry, 1975 .-- 223 p.

4. Korshun M.O., Klimova V.A. / SUCH. - 1951.V.6. Number 4. - 230 p.

5. Collection of methods for microanalysis of various compounds / Ed. ON. Isakova. - L .; VNIISK, 1968 .-- 104 p.

6. Kalinina L.S., Motorina M.A., Nikitina N.I., Khachapuridze N.A. Analysis of condensed oligomers. - M .: Chemistry, 1984. - 296 p.

7. Tarasov A.E. Investigation of the kinetics and polymerization mechanism of substituted oxetanes under the influence of boron trifluoride etherate in the presence of ethylene glycol. - Abstract of the dissertation for the degree of candidate of chemical sciences. Chernogolovka - 2011 - 8-9 s.

Claims (1)

The method for determining the elemental composition of oligomers based on 3,3-bis (azidomethyl) oxetane (BAMO), characterized in that the determination of the elemental composition of oligomers based on BAMO is carried out by the optical density of the absorption bands of the IR spectrum of the samples in the form of a film prepared from molten oligomer or its solution in dimethylformamide, in the region of 400-4000 cm ^-1 , which determines the content of nitrogen, carbon, hydrogen, oxygen and chlorine in the samples under study according to the intensity of the absorption bands of the N ₃ group, CCl groups with respect to opt nical densities CH ₂ - or COC-groups, wherein the nitrogen is determined by plotting the ratio of absorbance bands N ₃ to the absorbance SOS the nitrogen content of the strip in the oligomer, carbon - by plotting the ratio of absorbance bands N ₃ to the absorbance COC strip on the ratio of nitrogen and carbon, hydrogen - by plotting the ratio of absorbance bands ₃ N to an absorbance band of the ratio of CH ₂ of nitrogen and hydrogen, oxygen - on schedule for isimosti the ratio of the optical density of band ₃ N to an absorbance band SOS on the ratio of nitrogen and oxygen, chlorine - by plotting the ratio of the optical density to CCl band absorbance band _CH2 residual chlorine content.

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