Effect of Ions on the Flow-Induced Crystallization of Poly(vinylidene fluoride)

Catalytic Thermal Decomposition of NO2 by Iron(III) Nitrate Nonahydrate-Doped Poly(Vinylidene Difluoride)

The products of thermal decomposition of iron nitrate nonahydrate doped into poly(vinylidene difluoride) are examined using Mössbauer spectroscopy. Very little of the expected nitrogen dioxide product is observed, which is attributed to Fe³⁺ catalysis of the decomposition of NO₂. The active site of the catalysis is shown to be Fe(OH)₃ in the polymer matrix, which is, unexpectedly, reduced to Fe(OH)₂. Thermodynamic calculations show that the reduction of Fe³⁺ is exergonic at sufficiently high temperatures. A reaction sequence, including a catalytic cycle for decomposition of NO₂, is proposed that accounts for the observed reaction products. The role of the polymer matrix is proposed to inhibit transport of gas-phase products, which allows them to interact with Fe(OH)₃ doped in the polymer.

Two-Stage Evolution of Gamma-Phase Spherulites of Poly (Vinylidene Fluoride) Induced by Alkylammonium Salt

We investigated the evolution of the γ-phase spherulites of poly(vinylidene fluoride) (PVDF) added to 1 wt% of tetrabutylammonium hydrogen sulfate during the isothermal crystallization at 165 °C through polarized optical microscopy and light scattering measurements. Optically isotropic domains grew, and then optical anisotropy started to increase in the domain to yield spherulite. Double peaks were seen in the time variation of the Vv light scattering intensity caused by the density fluctuation and optical anisotropy, and the Hv light scattering intensity caused by the optical anisotropy started to increase during the second increase in the Vv light scattering intensity. These results suggest the two-stage evolution of the γ-phase spherulites, i.e., the disordered domain grows in the first stage and ordering in the spherulite increases due to the increase in the fraction of the lamellar stacks in the spherulite without a change in the spherulite size in the second stage. Owing to the characteristic crystallization behavior, the birefringence in the γ-phase spherulites of the PVDF/TBAHS was much smaller than that in the α-phase spherulites of the neat PVDF.