Composite materials based on dental acrylic plastic and Chimica Techno Acta LETTER published by Ural Federal University 2021, vol. 8(4), № 20218413 eISSN 2411-1414; chimicatechnoacta.ru DOI: 10.15826/chimtech.2021.8.4.13 1 of 3 Composite materials based on dental acrylic plastic and chitosan L.A. Yakovishin * , E.V. Tkachenko Sevastopol State University, 299053 University st., 33, Sevastopol, Russia * Corresponding authors: chemsevntu@rambler.ru This short communication (letter) belongs to the MOSM2021 Special Issue. © 2021, The Authors. This article is published in open access form under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Abstract Chitosan and poly(methyl methacrylate) (PMMA) composites were synthesized by polymerization with heating and mechanochemical method. The obtained polymer composites were analyzed by the ATR FT-IR spectroscopy method. The presence of intermolecular hydro- gen bonds and hydrophobic interactions in formation of PMMA and chitosan polymer composites was shown. Keywords polymer composites poly(methyl methacrylate) chitosan FT-IR spectroscopy Received: 03.11.2021 Revised: 16.12.2021 Accepted: 16.12.2021 Available online: 17.12.2021 1. Introduction New composites are currently being actively studied [1–3]. Such materials may be promising for use in various fields of medicine. For example, composite materials are widely used in modern dentistry [1]. Poly(methyl methacrylate) or poly(methyl 2-methylpropenoate) (PMMA) is one of the most im- portant polymers in industry and medicine [1, 4]. PMMA is widely used in dentistry practice for the fabrication of dentures [4]. On the basis of PMMA, heat-curing acrylic resins for removable prostheses, cold-curing resins for frameworks and self-curing resins for denture repairs and for custom trays have been developed [5, 6]. However, PMMA can have a toxic effect on the human body, which is accompanied by allergic reactions and impaired oral mi- croflora [7]. Polysaccharide chitosan is used for obtaining new bio- medical materials [8, 9]. Chitosan has antitumoral, antiox- idative, bacteriostatic and fungistatic properties [8]. Ear- lier, various composites of chitosan with gelatin [10], clay [9] and other substances were prepared. In addition, a block copolymer of chitosan with PMMA was ob- tained [11]. This article is devoted to the preparation of composite materials based on PMMA and chitosan. 2. Experimental Low-molecular water-soluble chitosan (freeze-dried pow- der; purity 88.4%; molecular weight 1–30 kDa) was pur- chased from Bioprogress (Russia). The source of PMMA was the Villacryl H Plus (Zhermack S.p.A., Poland). 2.1. Preparation of composites Preparation of composite 1. 1 g of chitosan and 1 g of Vil- lacryl H Plus were stirred for 1 min, 0.44 ml of PMMA monomer was added to the resulting mixture, stirred for 10 min at room temperature, and heated at 60 °C for 60 min. Preparation of composite 2. 1 g of chitosan and 1 g of Villacryl H Plus were stirred for 1 min, 0.44 ml of PMMA monomer was added to the resulting mixture, stirred for 10 min at room temperature and heated at 60 °C for 30 min. Then the temperature was raised to 100 °С and the mixture was heated for another 30 min. Preparation of composite 3. 1 g of chitosan and 1 g of Villacryl H Plus were grinded in an agate mortar for 120 min. To the resulting mixture was added 0.44 ml of PMMA monomer, stirred for 10 min at room temperature and heated at 60 °C for 30 min. Then the temperature was raised to 100 °C and the mixture was heated for another 30 min. The powders of the obtained composites were cooled to room temperature and investigated by the FT-IR spectros- copy method. The IR spectra were recorded on the Simex FТ- 801 IR-Fourier spectrometer (Russia) in the 4000–550 cm–1 region (spectral resolution 4 cm–1; 25 scans) using the ATR accessory with diamante crystal plate. Photos of the com- posites were obtained using the ATR accessory with built- in lens (Simex, Russia) at 60x magnification. http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2021.8.4.13 https://orcid.org/0000-0002-8728-7950 https://orcid.org/0000-0002-7041-5792 http://creativecommons.org/licenses/by/4.0/ Chimica Techno Acta 2021, vol. 8(4), № 20218413 LETTER 2 of 3 2.2. IR spectra IR spectrum of PММА (, cm–1): 2998 (СН), 2948 (СН), 2853 (СН), 1719 (С=О), 1474 (СН), 1458 (СН), 1432 (СН), 1387 (СН), 1364 (СН), 1322 (СН), 1268 (С–О–С), 1237 (С–О–С), 1188 (СО–О–СН3, СН), 1140 (С–О–С), 1059 (С–О–С), 984 (С–С), 962 (С–С), 912 (СН), 839 (СН), 809 (С=О), 747 (С=О, СН), 692 (СН). IR spectrum of chitosan (, cm–1): 3310 (ОН, NH), 2869 (СН), 2836 (СН), 1655 (C=OAmid I), 1619 (NH2), 1609 (NH2), 1602 (NH2), 1543 (N–H+С–NAmid II), 1516 (N–H+С–NAmid II), 1509 (N–H+С–NAmid II), 1501 (N–H+С–NAmid II), 1489 (СН), 1474 (CH), 1418 (СН), 1379 (СН), 1339 (CH), 1317 (N–H+С–NAmid III, CH), 1260 (C–O–C, OH, С–N), 1244 (C–O–C, C–OH), 1149 (C–O–C, C–OH), 1057 (C–O–C, C–OH), 1015 (C–O–C, C–OH), 995 (C–O–C, C–OH, С–С), 889 (CH), 720 (NHAmid V), 679 (NH2), 661 (OH), 635 (CH), 617 (O=C–NAmid IV), 603 (CH), 567 (NH, CO). IR spectrum of composite 1 (, cm–1): 3297 (ОН, NH), 2989 (СН), 2948 (СН), 2888 (СН), 2836 (СН), 1731 (С=ОPMMA), 1715 (С=ОPMMA), 1654 (C=OAmid I), 1636 (NH2), 1623 (NH2), 1610 (NH2), 1558 (NH2), 1542 (N–H+С–NAmid II), 1517 (N–H+С–NAmid II), 1508 (N–H+С–NAmid II), 1488 (СН), 1474 (СН), 1451 (СН), 1433 (СН), 1418 (СН), 1397 (СН), 1387 (СН), 1379 (СН), 1363 (СН), 1339 (CH), 1318 (N–H+С–NAmid III, CH), 1296 (СН), 1268 (С–О–С, OH, С–N), 1239 (С–О–С, C–OH), 1188 (СО–О–СН3, СН), 1145 (С–О–С, C–OH), 1086 (С–О–С, C–OH), 1060 (С–О–С, C–OH), 1034 (C–O–C, C–OH), 1012 (C–O–C, C–OH), 991 (C–O–C, C–OH, С–С), 966 (С–С), 943 (СН), 838 (СН), 812 (С=О), 747 (С=О, СН), 720 (NHAmid V), 686 (CH), 679 (NH2), 660 (OH), 636 (CH), 618 (O=C–NAmid IV), 602 (CH), 572 (СH), 558 (NH, CO). IR spectrum of composite 2 (, cm–1): 3247 (ОН, NH), 2996 (СН), 2947 (СН), 2865 (CH), 1732 (С=ОPMMA), 1716 (С=ОPMMA), 1698 (С=ОPMMA), 1647 (C=OAmid I), 1636 (NH2), 1623 (NH2), 1617 (NH2), 1609 (NH2), 1557 (NH2), 1541 (N–H+С–NAmid II), 1522 (N–H+С–NAmid II), 1507 (N–H+С–NAmid II), 1497 (N–H+С–NAmid II), 1489 (СН), 1473 (СН), 1456 (СН), 1435 (СН), 1419 (СН), 1396 (СН), 1387 (СН), 1374 (СН), 1362 (СН), 1339 (CH), 1319 (N–H+С–NAmid III, CH), 1268 (С–О–С, OH, С–N), 1241 (С–О–С, C–OH), 1186 (СО–О–СН3, СН), 1141 (С–О–С, C–OH), 1090 (С–О–С, C–OH), 1060 (С–О–С, C–OH), 1028 (C–O–C, C–OH), 1012 (C–O–C, C–OH), 985 (C–O–C, C–OH, С–С), 968 (С–С), 905 (СН), 839 (СН), 807 (С=О), 747 (С=О, СН), 720 (NHAmid V), 696 (CH), 681 (NH2), 650 (OH), 617 (O=C–NAmid IV), 601 (CH), 572 (СH), 562 (NH, CO). IR spectrum of composite 3 (, cm–1): 3239 (ОН, NH), 3031 (СН), 2993 (СН), 2951 (СН), 2801 (СН), 1720 (С=ОPMMA), 1655 (C=OAmid I), 1638 (NH2), 1627 (NH2), 1619 (NH2), 1610 (NH2), 1561 (NH2), 1542 (N–H+С–NAmid II), 1523 (N–H+С–NAmid II), 1509 (N–H+С–NAmid II), 1499 (N–H+С–NAmid II), 1474 (СН), 1458 (СН), 1449 (СН), 1432 (СН), 1419 (СН), 1396 (СН), 1387 (СН), 1376 (СН), 1365 (СН), 1338 (CH), 1323 (N–H+С–NAmid III, CH), 1297 (СН), 1267 (С–О–С, OH, С–N), 1239 (С–О–С, C–OH), 1185 (СО–О–СН3, СН), 1139 (С–О–С, C–OH), 1102 (С–О–С, C–OH), 1082 (С–О–С, C–OH), 1062 (С–О–С, C–OH), 1029 (C–O–C, C–OH), 1016 (C–O–C, C–OH), 987 (C–O–C, C–OH, С–С), 961 (С–С), 917 (СН), 838 (СН), 814 (С=О), 798 (СН), 780 (СН), 747 (С=О, СН), 723 (NHAmid V), 694 (CH), 684 (NH2), 654 (OH), 620 (O=C–NAmid IV), 607 (CH), 573 (СH), 561 (NH, CO). 3. Results and discussion Composites of chitosan and PMMA were obtained by in situ polymerization with heating at different temperatures (Fig. 1). To obtain composite 3, mechanochemical activation was preliminarily carried out by grinding chitosan and PMMA powders for 120 min. The source of PMMA was the Villacryl H Plus heat-curing acrylic resin for denture bases [6]. The resulting composites were analyzed by ATR FT-IR spectroscopy. It is often used to research composite mate- rials [10]. a b Fig. 1 Photo of the PMMA-chitosan composite 3 (a) and ATR FT-IR spectra of PMMA, chitosan and PMMA-hitosan composite 3 (b) Chimica Techno Acta 2021, vol. 8(4), № 20218413 LETTER 3 of 3 The IR spectra of chitosan and PMMA composites show low-frequency shifts of the absorption band of stretching vibrations of О–Н and N–H bonds in chitosan from 3310 cm–1 to 3297 cm–1 (for composite 1), to 3247 cm–1 (for composite 2) and to 3239 cm–1 (for composite 3; Fig. 1). Such changes in the spectra confirm the formation of hy- drogen bonds. In addition, IR spectra of composites 1–3 show certain changes related to the absorption bands of stretching vi- brations of С–О bonds in С–О–С and С–ОН groups, as well as to the in-plane bending vibrations of О–Н bonds in chi- tosan: 12601268, 12441239, 11491145, 10571060, 10151012, 995991 cm–1 (for composite 1), 12601268, 12441241, 11491141, 10571060, 10151012, 995985 cm–1 (for composite 2), and 12601267, 12441239, 11491139, 10571062, 995987 cm–1 (for composite 3). In this case, the most significant shifts were noted for the composites 2 and 3. The main absorption band of C=O stretching vibrations in PMMA ester bond was found at 1715 cm–1 (composite 1), at 1716 cm–1 (composite 2) and at 1720 cm–1 (composite 3). Moreover, additional bands are observed at 1698 and 1732 cm–1 (for composite 1), and at 1731 cm–1 (for compo- site 2). The presence of low-frequency shifts in the IR spectra is indicative of involving С=О group of PMMA in hydrogen bonding with chitosan. High-frequency shifts of some absorption bands of in- plane bending vibrations of N–H bonds in the chitosan molecule are observed in the spectra of composites: 16021610 cm–1 (for composite 1), 16021609 cm–1 (for composite 2), 16231627 cm–1 (for composite 3). In addi- tion, the IR spectra show shifts of the main absorption bands of stretching vibrations of CH bonds, which can be caused by hydrophobic interactions during the formation of composites. 4. Conclusions Polymer composites of PMMA and chitosan were obtained by polymerization with heating and mechanochemical method. The composites 1–3 are formed due to hydrogen bonds (C=OPMMA…H–OChitosan and C=OPMMA…H–NHChitosan) and hydrophobic interactions. It is possible that the pres- ence of chitosan in composite materials can change some of their mechanical properties and eliminate the toxicity of PMMA. 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