Vinylidene fluoride telomers for piezoelectric devices

Temperature Dependence of the Number of Defect-Structures in Poly(vinylidene fluoride)

Poly(vinylidene fluoride) (PVDF) is predominantly characterized by alternating CH2 and CF2 units in a polymer backbone, originating from the head-to-tail addition of monomers or regular propagation. Due, to a small extent, to inverse monomer addition, so-called defect structures occur which influence the macroscopic properties of PVDF significantly. The amount of defect structures in the material is determined by the polymerization conditions. Here, the temperature dependence of the fraction of defect structures in PVDF obtained from polymerizations between 45 and 90 °C is reported. We utilized 19F-NMR spectroscopy to determine the fraction of defect structures as a function of temperature. To derive kinetic data, the polymerization of VDF is considered a quasi-copolymerization described by the Terminal Model involving four different propagation reactions. Based on the experimentally determined temperature-dependent fractions of defect structures, the known overall propagation rate coefficient, and taking into account the self-healing behavior of the macroradical, the Arrhenius parameters of the individual propagation rate coefficients were determined using the Monte Carlo methods.

Vinylidene fluoride polymerization by metal-free selective activation of hydrogen peroxide: microstructure determination and mechanistic study

Hydrogen peroxide-initiated radical polymerization of vinylidene fluoride (VDF) at 130 °C in dimethyl carbonate is presented.

High-performance membranes with full pH-stability

Following current strong demands from, among others, paper, food and mining industries, a novel type of nanofiltration membrane was developed, which displays excellent performance in terms of selectivity/flux with a unique combination of chemical stability over the full (0-14) pH-range and thermal stability up to 120 °C. The membrane consists of polyvinylidene fluoride grafted with polystyrene sulfonic acid. The optimum membrane showed water permeances of 2.4 L h-1 m-2 bar-1 while retaining NaCl, MgSO4 and Rhodamine B (479 Da) for respectively ≈60%, ≈80% and >96%.

Synthesis of Chlorotrifluoroethylene-Based Block Copolymers by Iodine Transfer Polymerization

Various fluorinated macro-chain transfer agents (CTAs) based on vinylidene fluoride (VDF), chlorotrifluoroethylene (CTFE), or CTFE and vinylidene chloride (VDC), were synthesized by iodine transfer polymerization (ITP). These macro-CTAs were involved in a further ITP reaction that led to the synthesis of original CTFE-based block copolymers exhibiting molecular weight ranging from 2500 to 40000 g/mol and endowed with high thermal stabilities (decomposition temperature at 10% weight loss of ca. 380 °C, under air). ITP of CTFE and VDC as well as ITP of VDF thermally initiated at 100 °C by a catalytic amount of dimanganese decacarbonyl (Mn₂(CO)₁₀) are reported for the first time.