T efficiency . Polyamide-imide (PAI) is a modified polyimide, which typically has repeated structural units (Scheme 1). It may be observed from the molecular DNQX disodium salt Autophagy structure that PAI contains two structural units, amide bond and imide ring, so PAI has some overall performance advantages over PA and PI, like high-temperature resistance, corrosion resistance, friction and wear resistance, fantastic mechanical properties, and can be compounded with a variety of substances, and so forth. PAI is usually a special engineering plastic with superb overall performance, which can be applied in really extreme functioning circumstances [5,6].Copyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access write-up distributed under the terms and conditions in the Inventive Commons Thromboxane B2 custom synthesis Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).Materials 2021, 14, 6376. https://doi.org/10.3390/mahttps://www.mdpi.com/journal/materialsMaterials 2021, 14,2 ofScheme 1. PAI molecular structural formula.PAI polymer synthesized by four,4′-diaminodiphenyl ether has far better extensive properties, along with the raw material is inexpensive, which has improved engineering application prospects. 2,2′-bis (trifluoromethyl)-4,4′-diaminophenyl ether has the exact same main chain structure as four,4′-diaminodiphenyl ether, and the side chain contains two trifluoromethyl groups, which has high fluorine content material. Studies have shown that introducing fluorine or fluorine-containing groups in to the molecular structure can decrease the moisture absorption price of supplies , boost the heat resistance [8,10], increase the wear resistance , boost the solubility , and so on. There have been couple of reports onthe effects of fluorine atoms and fluorine-containing groups on PAI. Within this paper, 2,2′-bis (trifluoromethyl)-4,4′-diaminophenyl ether and 4,4’diaminodiphenyl ether have been compounded to synthesize PAI by the acyl chloride approach [5,15]. The effects of trifluoromethyl on heat resistance, friction and wear resistance, hydrophobicity, and mechanical properties of PAI components have been studied to prepare PAI components with great properties. 2. Experimental two.1. Supplies four,4′-diaminodiphenyl ether was analytically pure and bought from Aladdin (Shanghai, China). 2,2′-bis (trifluoromethyl)-4,4′-diaminophenyl ether was analytically pure and purchased from Changzhou Sunshine Pharmaceutical Technology Co., Ltd. (Changzhou, China). 1,two,4-trimellitic anhydride acyl chloride(TMAc) was purchased from Tokyo Chemical Industry (Tokyo, Japan). Triethylamine as an acid-binding agent and catalyst was purchased from Aladdin (Shanghai, China). Acetic anhydride was analytically pure, utilised as dehydrating agent, bought from Aladdin (Shanghai, China). N-methylpyrrolidone(NMP) as aprotic polar solvent was purchased from Aladdin (Shanghai, China). two.2. Preparation of PAI PAI synthesized by 4,4′-diaminodiphenyl ether and TMAC was named PAI(O). When the molar ratio of four,4′-diaminodiphenyl ether to 2,2′-bis (trifluoromethyl)-4,4′-diaminophenyl ether is (9:1), (7:3), (five:5), (three:7) and (1:9), the synthesized PAI terpolymers have been named PAI-1,PAI-2,PAI-3,PAI-4,PAI-5 in turn.PAI synthesized by two,2′-bis (trifluoromethyl)-4,4’diaminophenyl ether and TMAC was named PAI(F).The preparation procedure was as follows: (1) Polymerization approach Under the protection of nitrogen, NMP was added into a 500 mL four-necked flask, and the level of NMP was eight times the total mass of trimellitic anhydride acyl chloride and diamine monomer.