Translated Abstract
Fluoropolymers possess numerous excellent properties including high resistance properties to thermal, chemical, ageing and weather, excellent inertness to solvents, acids and alkalis, hydrocarbons, low flammability, low refractive index, low surface energy. Most of these properties are linked to its small Van Der Waals radius (1.32 Å) and to the strong C-F bond (485 kJmol-1). Preparation of functional fluorine materials through chemical modification of commercial fluoropolymers has been recognized as an economic and convenient strategy to expand the application field of fluoropolymers. Crosslinking has been well recognized as a useful method to improve the mechanical performance of fluoroelastomers at high temperature since sulfur was first utilized in curing rubber in 1840. The most utilized curing way of fluoropolymers is by the nucleophiles such as diamines or bisphenols, electron radiation and peroxide. However, the final fluoropolymer products cured with these processes usually contain many small molecular impurities and the main chain degradation, which would lead to significantly reduced insulating properties of fluoropolymers and are not desirable for the high electric field applications. Therefore, curing fluoropolymers in a more facile and clean strategy to achieve high insulating performance at high temperature is still a challenge for the chemists.
In this dissertation, thermally self-curable fluoroelastomer containing both coupled TEMPO and unsaturated bonds has been successfully synthesized in one-pot by ARGET-ATRP from original P(VDF-co-CTFE)(80/20). This strategy involves two competitive processes including the coupling reaction between macro-radicals and TEMPO and the dehydrochlorination of commercially available P(VDF-co-CTFE) by the route of three-molecule process together with a small portion of the elimination curred in E2 mechanism and β-H elimination. The structure and properties of the objective polymer were demonstrated by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC). The two competitive reaction processes were carefully investigated under varied reaction conditions including the different reaction temperature, reaction time, ligand, solvents, copper salt, and the dosage of TEMPO. The resultant polymer is rather stable at ambient temperature and easily cured at high temperature (above 150 oC) by pulling the trigger, namely breaking C-O or O-N bonds, and the free radicals generated in situ are responsible for initiating the crosslinking of double bonds on polymer main chain. No other additives are required for the crosslinking of the resultant polymer, which provides a facile chemical route to prepare crosslinked fluoropolymers with high purity, significant improved solvent resistance and excellent mechanical properties.
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