An unsaturated room-temperature ionic liquid (IL), 1-vinyl-3-butylimidazolium chloride [VBIM][Cl], has been grafted onto poly(vinylidene fluoride) (PVDF) by electron beam irradiation at room temperature. The structure and physical properties of IL grafted PVDF (PVDF-g-IL) were investigated. Both the extraction experiments and 1 H NMR results indicated the successful grafting of IL onto PVDF molecular chains. It was calculated that IL grafting yield was approximately 3.9 per 100 repeating units of PVDF, suggesting very short IL grafting sequences. The melting temperatures (T m ) of the PVDF-g-IL films decreased with absorbed dose, suggesting the occurrence of crystal defects of PVDF caused by the irradiation. However, the morphologies, crystal forms and crystal long periods (L) of PVDF-g-IL films were not significantly influenced by the irradiation. Moreover, the effects of IL grafting and absorbed dose on physical properties of PVDF-g-IL films were investigated. It was found that the irradiation could immobilize IL molecules onto PVDF chains and thus suppressed their migration in electric filed. Therefore, the grafted samples showed lower dielectric loss, electrical conductivity as well as dielectric permittivity compared with the unirradiated blends. Moreover, the elongation at break of the grafted PVDF decreased with the applied irradiation dose, but the Young's modulus increased. The as-prepared PVDF-g-IL composites exhibited large dielectric permittivity, low dielectric loss and, in particular, excellent toughness, which is promising for use in dielectric capacitor applications.

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Here, we fabricated the ionic liquid (IL) grafted poly(vinylidene fluoride) (PVDF) (PVDF-g-IL) via electron-beam irradiation to fight common bacteria and multidrug-resistant "superbugs". Two types of ILs, 1-vinyl-3-butylimmidazolium chloride (IL (Cl)) and 1-vinyl-3-ethylimidazolium tetrafluoroborate (IL (BF)), were used. It was found that the PVDF-g-IL exhibited superior antibacterial performance, with almost the same mechanical and thermal performance as unmodified PVDF. Nonwovens and films made from PVDF-g-IL materials exhibited broad-spectrum antimicrobial activity against common bacteria and "superbugs" with the strong electrostatic interactions between ILs and microbial cell membranes. With extremely low IL loading (0.05 wt %), the cell reduction of PVDF-g-IL (Cl) nonwovens improved from 0.2 to 4.4 against S. aureus. Moreover, the antibacterial activity of PVDF-g-IL nonwovens was permanent for the covalent bonds between ILs and polymer chains. The work provides a simple strategy to immobilize ionic antibacterial agents onto polymer substrates, which may have great potential applications in healthcare and household applications.

Nanostructured polymeric dielectric composites, based on poly­(vinylidene fluoride) (PVDF), conductive carbon black (CB), and an unsaturated ionic liquid (IL), 1-vinyl-3-ethyl­imidazolium tetrafluoro­borate ([VEIM]­[BF4]), were fabricated by melt blending and electron beam irradiation (EBI) methods. Our strategy forms simultaneous double nanophases in the PVDF matrix, that is, homogeneously dispersed CB nanoparticles and organic PVDF-g-IL nanodomains. The organic nanodomains were produced by microphase separation of the PVDF-g-IL chains from the PVDF matrix at melt state in the electron beam (EB) irradiated PVDF/IL-CB nanocomposites. Furthermore, the CB nanoparticles were fully adhered with these nanodomains, and novel structures with nanodomains@CB nanoparticle were achieved. Such nanodomains@CB nanoparticle structures showed a synergetic nucleating effect on the PVDF crystallization and led to the formation of dominant nonpolar α phases in the nano-PVDF/IL-CB composites. Because of the nanodomains adhesion of the CB nanoparticles, the nano-PVDF/IL-CB composites displayed a drastic reduction in dc conductivity compared with that of PVDF/CB and PVDF/IL-CB composites, respectively. Importantly, the resultant nano-PVDF/IL-CB composites exhibited significantly decreased losses relative to that of PVDF/CB, PVDF/IL, and PVDF/IL-CB composites. The structures of nanodomains@CB nanoparticle can be well responsible for this improvement of dielectric performance due to the fact that nanodomains confined the ion movements of IL in electric field and that their adhesion to the CB nanoparticle surfaces largely hindered the direct CB–CB nanoparticle contacts, thus decreasing their leakage currents. Our strategy not only fabricates PVDF/CB dielectric materials with good CB dispersion, higher dielectric permittivity, lower conductivity, and lower loss but also paves a new strategy for fabricating nanocomposites with double nanophases in polymer matrix.

Flexible dielectric materials with high dielectric constant and low loss have attracted significant attention. In this work, we fabricated novel polymer-based nanocomposites with both homogeneously dispersed conductive nanofillers and ion-conductive nanodomains within a polymer matrix. An unsaturated ionic liquid (IL), 1-vinyl-3-ethylimidazolium tetrafluoroborate ([VEIM][BF 4 ]), was first coated on the surface of multi-walled carbon nanotubes (CNTs) by the mechanical grinding. The ILs coated CNTs were then well dispersed in poly(vinylidene fluoride) (PVDF) matrix by melt-blending. The ILs on the surface of CNTs were subsequently grafted onto the PVDF chains by electron beam irradiation (EBI). The formed ILs grafted PVDF (PVDF-g-IL) finally aggregated into ionic nanodomains with the size of 20-30 nm in the melt state. Therefore, novel PVDF nanocomposites with both homogenously dispersed CNTs and ionic nanodomains were achieved. Both carbon nanotubes and ionic nanodomains contributed to the enhancement of the dielectric constant of PVDF significantly. At the same time, such homogeneously dispersed CNTs along with the confined ions in the nandomains decreased current leakage effectively and thus led to the low dielectric loss. The final PVDF nanocomposites exhibited high dielectric constant, low dielectric loss and good flexibility, which may be promising for applications in soft/flexible devices.