Towards new environmentally friendly fluoroelastomers: from facile chemical degradation to efficient photo-crosslinkable reaction

Our objective is to develop a versatile and facile method that allows the synthesis of novel primary fluorinated co-oligomers as precursors of photo-crosslinkable networks. Transparent carboxyl-terminated fluorinated co-oligomers with molecular weights ranging between 2000 and 10 400 g mol⁻¹ were synthesized via facile degradation. The structural changes of fluorinated backbone were investigated using various analysis techniques. Then two major approaches, namely esterification and ring opening, were applied to obtain photochemical diacrylates (HEMA- and GMA-IEM-terminated co-oligomers). These two precursors can be cured in 60 s under UV radiation without high temperature, high pressure or toxic solvent. The glass transition temperatures of HEMA- and GMA-IEM-terminated fluoropolymers at about −20 °C, assessed from differential scanning calorimetry, showed an increase after crosslinking, and the glass transitions at 20 °C were no longer observed. These two crosslinked films were found to have higher decomposition temperatures, when compared to starting precursors. The contact angles on the surface of the two elastomer materials were only about 74° and 78°, which increased to 105° and 110° after UV irradiation. The tensile strength of the two cured fluoroelastomers can still reach 1.3 MPa at 200 °C.