Structural evolution of PVDF during storage or annealing

Abstract

The effect of annealing PVDF at temperatures above T g and below T m was investigated by differential scanning calorimetry (DSC), thermostimulated current spectroscopy (TSC) and solidstate NMR. This study evidences a progressive structural evolution, taking place during such annealing. Its characteristics (kinetics and its temperature dependence, lack of reversibility at lower temperature over extended periods of time, double organization corresponding to double annealing with unmodified kinetics) point to a mechanism of secondary crystallization as described by Marand et al. In addition to the formation of extra crystalline (hence rigid) material, this phenomenon is believed to generate increasing conformational constraints in the residual amorphous material. Accordingly, a progressive reduction of the molecular mobility was demonstrated by NMR during annealing.

Mn2(CO)10-photomediated synthesis of poly(vinylidene fluoride)-b-poly(styrene sulfonate)

“…Interestingly, PVDF-b-PNeoSS displays an endothermic peak which could be related to the thermal history of the sample, such a PVDF crystallization before melting overlapping with NeoSS decomposition. As expected [80], the DSC of the annealed (i.e. deprotected PVDF-b-PSSA is featureless, although a minor peak at 175°C may still be distinguished and associated with the melting of the PVDF block.…”

“…7. In the case of pure PVDF-I, there is visible a small peak at ca 85°C, which could be assigned [80] to various processes as upper glass transitions, internal crystallinity [76]). The DSC curve of PNeoSS homopolymer indicates an endothermic process at ca 140°C, which most likely originates from the onset of the thermal decomposition of the neopentyl styrene sulfonate units followed by very rapid decomposition above 160°C.…”

Effect of crystallinity on surface morphology and light transmittance of poly(vinylidene fluoride‐co‐hexafluoropropylene) thin film

“…16 Polymers were dissolved in DMF at room temperature for 1 day to obtain homogeneous solutions. The concentrations were ranged from 16 to 20 wt % to adjust the thickness of thin films around 1 lm.…”

Effects of mixed diluent compositions on poly(vinylidene fluoride) membrane morphology in a thermally induced phase‐separation process

“…6) has been employed for investigating the crystallization behavior of the PVDF membrane, and it shows that multiple melt peaks are present for all three representative samples and that the height and temperature of the first peak (weak peak) increase as the DOP content increases. The multiple melting phenomenon of crystalline polymers has been reported in many publications, 19,20 and its formation mechanism is complicated. The variation of the morphology, perfection of crystals, polymorphism, and recrystallization all can lead to a multiple melting phenomenon.…”