Understanding of Versatile and Tunable Nanostructuration of Ionic Liquids on Fluorinated Copolymer

Abstract

International audienceA fundamental understanding of the versatile and tunable nanostructuration effect of two phosphonium ionic liquids (ILs), denoted octadecyltriphenylphosphonium iodide (IL-C18) and tributyl(methyl)phosphonium methylsulfate (IL-108), on a semicrystalline fluorinated copolymer poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) was elaborated. This research suggests that the nanostructuration mechanism is very dependent on the diffusion and interacting abilities of ILs in matrix, which are determined by the chemical structures of ILs. Both LLs appear to diffuse and regularly assemble in the rigid amorphous fraction (RAF) of P(VDF-CTFE) between crystalline lamellae thanks to the "template" confinement effect of 2D structure. The assembled structure shows a gradually regular ID to 2D geometric evolution with increasing the ILs amount revealed by Porod exponents in SANS analyses. Simultaneously, these regularly assembled ILs in the RAF also act as "template" to efficiently induce a complete transition of nonpolar alpha-phase to polar gamma- and/or beta-phase with only a tiny amount of ILs (from 2 wt %) (by XRD and FTIR). Moreover, the crystallization displays a depression behavior with reduced T-c, T-m, crystallinity (by DSC), and crystallite size (by SANS) due to the existence of ILs in the RAF seen as obstacle for the regular chain-folding and the dipolar interaction with P(VDF-CTFE). We propose that the synergistic influence of mutual "templates" endues phosphonium ILs a versatile nanostructuration on the fluorinated matrix. Moreover, this versatile nanostructuration effect can be easily tuned by tailoring the chemical structures of ILs. The difference in the chemical structures of ILs endows them different diffusion rates upon crystallization from solution for preparing resulting blend films and strengths of dipolar interaction with P(VDF-CTFE), consequently affecting their dispersion state in the matrix to reside in the RAF with different extents and interacting abilities (confirmed by IDEA and DMA). Thus, IL-108 with faster migration rate and stronger dipolar interaction than IL-C18 (due to the smaller steric hindrance and extra polar groups in the cation/anion combination of the IL structure) locates in the RAF much more to induce more trans-configuration (beta-phase), more homogeneous dispersion morphology, and higher depression of crystallization

Effect of polyvinylidene fluoride electrospun fiber orientation on neural stem cell differentiation

“…Then, combining the FTIR data with the X‐ray diffraction (XRD) spectra, it can be concluded that a very high content of β phase is obtained for the electrospun PVDF nanofibers. In fact, the presence of diffraction peaks at 20.7° (200/110) and 36.6° (101) suggesting that the use of electrospinning process induces the all‐trans β crystal conformation . Nevertheless, despite the decrease of the diffraction peak at 18.6° (002) of the electrospun fibers, the α phase is always present.…”

“…In addition, the absorption intensity of the band at 840 cm −1 significantly increases with the increase of the fibers orientation. According to the literature from Yang et al, this band corresponds to the absorbance of trans segments longer than TT, suggesting that nonpolar α phase is converted to polar β phase …”

“…In all cases, the weight of samples was between 5 and 10 mg. The values of the crystallinity χ c (%) were calculated with the melting enthalpy and the enthalpy of fully crystalline phase for PVDF, that is, 104.9 J g −1 …”

P (VDF‐co‐CTFE)‐g‐P2VP amphiphilic graft copolymers: Synthesis, structure, and permeation properties

“…In all the samples, two diffraction peaks were observed at 2θ = 17.9° and 20.0°, regardless of the solvent used. These peaks correspond to α‐crystal planes with Miller indices of (100) and (110), respectively, in PVDF‐ co ‐CTFE . When comparing the two solvents, the peak at 26.7°, which is assigned to the α (021) plane, was observed in only those membranes prepared with NMP.…”

Local Grafting of Ionic Liquid in Poly(vinylidene fluoride) Amorphous Region and the Subsequent Microphase Separation Behavior in Melt

“…Recently, investigations on poly(vinylidene fluoride) (PVDF) modified by room temperature ionic liquids (ILs) have been widely reported in the literatures . The incorporation of ILs leads to the formation of electroactive phases ( β or γ phase) of PVDF . PVDF/IL blends have the potential applications as solid polymer electrolytes, actuators, biomedical devices, and smart materials .…”