Efficient sensitizer-supported electron beam irradiation induced crosslinking of polyvinylidene fluoride for shape memory applications

Abstract

Abstract Polyvinylidene fluoride (PVDF) preferentially crosslinks upon exposure to ionizing electron beam irradiation, leading to substantial changes in its physicomechanical and thermophysical properties. However, low dose electron beam irradiation produces inefficient crosslinking in pure PVDF while high dose irradiation tends to induce the concomitant process of transverse bond degradation. This has been addressed by incorporating a sensitizer into PVDF to increase crosslinking efficiency under low dose irradiation. However, conventional sensitizers typically suffer from self-polymerization and the release of toxic volatile gases at high temperature, which diminishes the crosslinking efficiency and is toxic. This issue is addressed here via a series of well-designed bismaleimide (BMI) sensitizers and incorporating these into PVDF films for facilitating chemical crosslinking reactions under low electron beam irradiation doses. Analysis indicates that the sensitizing action of the proposed BMI sensitizers may be due to the formation of transverse bonds between vinylene groups and PVDF chains. Versus conventional triallyl isocyanurate and trimethylolpropane triacrylate sensitizers, the proposed BMI sensitizers facilitate high radiation crosslinking efficiency and exhibit good compatibility. Accordingly, the proposed sensitizers leading to irradiated PVDF films with outstanding thermomechanical performance and shape memory functionality.