Synthesis and research of polyfunctional silicon-containing amines – new promoters of adhesion 199 D O I: 1 0. 15 82 6/ ch im te ch .2 02 0. 7. 4. 11 K. Yu. Ivanova, Kuzmin M. V., N. I. Kol’tsov Chimica Techno Acta. 2020. Vol. 7, no. 4. P. 199–203. ISSN 2409–5613 Synthesis and research of polyfunctional silicon- containing amines — new promoters of adhesion K. Yu. Ivanova*, M. V. Kuzmin, N. I. Kol’tsov Chuvash State University named after I. N. Ulyanov 15 Moskovskii pr., Cheboksary, 428015, Russia *email: cool.karakyrt@ya.ru Abstract. Currently, in order to obtain high-tech hybrid products, modern adhe- sives have high requirements for creating strong joints between dissimilar materials. It is known that adhesion depends on the compatibility of the adhesives with the surfaces of the materials. Amine compounds are the main hardeners for epoxy compositions. That is why, in this article, we synthesized silicon-containing amines based on polyfunctional aminoalkoxysiloxanes for epoxy compositions. Aminoalkoxysiloxanes were prepared by the interaction of 3-aminopropyltriethoxysilane with monoethanolamine in nitrogen at atmospheric pressure in the presence of a binary antioxidant and catalytic amounts of an alkali metal alcoholate. During the reaction in a homogeneous phase, the reac- tion mixture was heated to a temperature of 100–110 °C and distilled off to 90% of ethanol from the theoretically calculated amount. Further, the reaction was carried out at a reduced temperature of 10–20 mmHg pressure until the release of alcohol stops. At the same time, gravimetric control was carried out and the refractive index of the reaction mixture was measured. As a result, aminoalkoxysilanes were obtained in the form of light-yellow oily liquids. The structure of the obtained compounds was investigated by IR spectroscopy on an FSM-1202 Fourier spectrophotometer and 1H NMR spectroscopy on a high-resolution BrukerWM-250 NMR spectrometer. It was found that under the selected synthesis conditions, aminopropyltri-(2-aminoethoxy)silane is ob- tained with the highest yield of 97.6% at a molar ratio of 3-aminopropyltriethoxysilane AGM-9 with monoethanolamine 1:3. Keywords: 3-aminopropyltriethoxysilane; aminoalkoxysiloxanes; adhesion promoters Received: 30.10.2020. Accepted: 07.12.2020. Published:30.12.2020. © K. Yu. Ivanova, Kuzmin M. V., N. I. Kol’tsov, 2020 Introduction Various types of aminosiloxanes are used to improve the adhesion charac- teristics of coatings, since silicon-contain- ing compounds can significantly improve the adhesion of polymer resins to substrates such as glass, silica, aluminum oxide and active metals [1, 2]. The advantage of epoxy compounds is their high adhesion capac- ity, low shrinkage, the possibility of cur- ing in a wide temperature range [3]. How- ever, epoxy compositions have a number of disadvantages: high brittleness, low heat resistance, which manifests itself in a de- crease in strength and stiffness at elevated temperatures. An increase in temperature at the moment of formation of the adhesive 200 contact leads to a decrease in viscosity and contributes to the achievement of the high- est adhesion strength. The  chemical na- ture of the adhesive plays a decisive role in the adhesion of the polymer to the met- al. It is  not the  number of  polar groups that is important, but the ability to enter into intense interaction with the surface groups of  the  substrate and the  ability to act as electron donors. The more clearly expressed the  electron-donor properties of functional groups, the higher their adhe- sion to metal [4]. Experimental It is  known that organosilicon com- pounds are biodegradable; they can in- crease the intensity of biological processes of oxidation of organic pollution of waste- water and thereby reduce the  anthropo- genic load on the environment [5–7]. For this, we synthesized organosilicon com- pounds — aminosiloxanes — as adhesion promoters, which can significantly increase the adhesive strength and water resistance of the adhesive bonds of epoxyamine coat- ings on various metal surfaces. Aminoalkoxysilanes I–III were ob- tained by the interaction of 3-aminopro- pyltriethoxysilane with monoethanolamine at  different molar ratios in  the  presence of a binary antioxidant and an alkali metal alcoholate. To do this, (ν1, mol) 3-amino- propyltriethoxysilane, (ν2, mol) pre-dis- tilled monoethanolamine are loaded into a reactor equipped with a stirrer, the reac- tion is carried out in the presence of an an- tioxidant and an alkali metal alcoholate, the mixture is kept at room temperature for 10  minutes, then evacuated at  tem- perature up to 100 °C for 10–20 minutes, until the alcohol is completely removed. The process was monitored by IR spectros- copy on an FSM-1202 Fourier spectropho- tometer. The structure of the obtained com- pounds was confirmed by the data of NMR spectroscopy, 1H NMR — high resolution spectra were obtained on a Bruker WM- 250 spectrometer in DMSO-d6, the internal standard was hexamethylenedisiloxane. Results and discussion In  this work, we have studied for the  first time the  process of  obtaining silicon-containing amines by  addition of  alkanolamines to  ethoxy-substituted derivatives, for example, to aminopropyl- triethoxysilane. Aminoalkoxysilanes I–III were ob- tained at different molar ratios of 3-ami- nopropyltriethoxysilane with monoetha- nolamine. For this, the calculated amount of  reagents was loaded into an  Arbuzov flask and heated in a nitrogen flow. The re- action begins in  a  heterogeneous phase, when a  certain temperature is  reached, the reaction mixture is homogenized (for example, at a ratio of 1:4, the homogeniza- tion temperature of the mixture is 104 °C). With a  further increase in  temperature, distillation of ethyl alcohol begins. With a  slow increase in  temperature, 80–90% of  the  theoretically calculated amount of alcohol (ethanol) was distilled off. Then, at  a  reduced pressure of  10–20 mmHg completed the  reaction until the  release of alcohol ceases. Аt the end of the pro- cess were performed gravimetric control and measurement of the refractive index of the reaction mixture. As a result, ami- noalkoxysilanes were obtained in the form of a light-yellow oily liquid. 201 Reactions of  3-aminopropyltriethox- ysilane with monoethanolamine in various mole ratios are presented below: Data on the  synthesis of  aminosilox- anes are given in Table. 1. Aminoalkoxysiloxanes were ob- tained as clear to light yellow oily liquids. In the IR spectra of the obtained products, there are intense absorption bands at 1081– 1085 cm–1, which are typical for Si-O-C bonds. The  absorption bands of  the  hy- droxyl group directly bonded to the sili- con atom are absent, and the bands cor- responding to the NH2 group are observed at 3275–3373 cm–1. In 1H NMR spectra of compounds I–III the signals related to the CH2Si were ob- sereved at 0.563 ppm, and signals of ami- no groups protons were observed at 2.50 ppm. In 1H NMR spectra of compounds I, II there were signals related to the vibra- tions of the Si-O-CH2 bond of 2-aminoeth- oxy and ethoxy groups at  3.33 ppm and 3.44 ppm, respectively. In  the  spectrum Si EtO EtO EtO NH2 HO NH2 Si O O O NH2H2N NH2 Si EtO EtO EtO NH2 HO NH2 Si EtO EtO EtO NH2 HO NH2 Si O O O NH2H2N H2N NH2 Si O O O NH2 H2N EtOH1. 2. 2 EtOH2 3. 3 EtOH3 (I) (II) (III) Table 1 The structure and properties of aminosiloxanes № Name ν1:ν2 Reaction yield, % nD 20 IR spectroscopy, ν, сm–1: NMR spectroscopy, d, ppm 1 3-aminopropyl- (2-aminoethoxy) diethoxysilane (I) 1:1 89.7 1.4440 3373, 3294 (NH2), 2974, 2927, 2883 (CH3, CH2), 1083 (Si-O-C) 0.563 s (2H, CH2Si), 1.058 t (6H, 2CH3), 2.50 s (4H, 2NH2), 2.546 m (2H, CH2CH2CH2), 2.547 t (4H, 2NH2CH2), 3.334 t (2H, 2H2NCH2CH2O), 3.443 (4H, 2 CH3CH2O). M 236.373 202 of compound III there were no vibrations of  the  protons of  the  ОCH2CH3 groups, which indicates the complete replacement of  the  ethoxy groups in  3-aminopropyl- triethoxysilane by 2-aminoethoxy groups. Conclusions To  sum up, aminoalkoxysiloxanes  — p oly f u n c t i on a l s i l i c on - c ont ai n i ng amines — have been synthesized, the struc- ture of which was confirmed by IR and 1H NMR spectroscopy. These aminoalkoxysi- loxanes are recommended for use as adhe- sion promoters. Acknowledgements This study was supported by Russian Foundation for Basic Research (RFBR), project number 20-33-90269. References 1. Rogozhina LG, Kuzmin MV, Ignatiev VA, Kolyamshin OA, Koltsov NI. Investigation of the effect of alkanolamines on the properties of epoxy anhydride compositions. Journal of Applied Chemistry. 2016;89(11):1481–7. doi:10.1134/S1070427216110161 2. Zagidullin AI, Kolpakova MV, Garipov RM, Stoyanov OV. Structure and properties of epoxy composites hardened with new silicon-containing amines. Glue. Sealants. Technology. 2008. (1):17–9. doi:10.1134/S1995421208030052 № Name ν1:ν2 Reaction yield, % nD 20 IR spectroscopy, ν, сm–1: NMR spectroscopy, d, ppm 2 3-aminopropyl-di- (2-aminoethoxy) ethoxysilane (II) 2:1 95.7 1.4521 3366, 3293 (NH2), 2971, 2927, 2875 (CH3, CH2), 1081 (Si-O-C) 0.56 s (2H, CH2Si), 1.06 t (3H, CH3), 2.50 s (6H, 3NH2), 2.335 t (4H, 2H2NCH2CH2O), 2.544 m (2H, CH2CH2CH2), 2.546 t (6H, 3NH2CH2), 3.334 ( 2H, CH3CH2O). M 251.388 3 3-aminopropyl-tri- (2-aminoethoxy) silane (III) 3:1 97.6 1.4650 1590 (Si- O-C); 3362, 3293 (NH2); 1083–1020 (Si-O) 0.57 s (2H, CH2Si), 2.50 s (8H, 4NH2), 2.544 m (2H, CH2CH2CH2), 2.546 t (8H, 4NH2CH2), 3.333 t (6H, 3H2NCH2CH2O). M 270.384 End of Table 1 203 3. Pradhan S, Mohanty S, Nayak S. Waterborne epoxy adhesive derived from epoxi- dized soybean oil and dextrin: synthesis and characterization. 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