Fluorine-19 solid-state NMR investigation of regiodefective semicrystalline α-poly(vinylidenefluoride)

Wormald, Philip; Apperley, David C.; Beaume, François; Harris, Robin K.

doi:10.1016/s0032-3861(02)00821-2

Cited by 25 publications

(63 citation statements)

References 33 publications

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“…A similar situation applies to T 1r (F), so that a post-CP 19 F spin-lock is equally effective in selecting such domains. Figure 10 [60] illustrates this fact and also shows that the selectivity extends to the spinning sidebands. The result suggests that some reverse units in PVDF occur in rigid regions (possibly at the interface of amorphous and crystalline domains).…”

Section: Applications To Fluoropolymersmentioning

confidence: 77%

“…This has been confirmed by the use of a post-CP 19 F spin-lock as a preparation phase to a RFDR experiment. [60] Experiments conducted at around 100 8C showed that T 1r (F) values for both the crystalline and amorphous domains of PVDF were significantly lower than those at approximately 60 8C but that the ratio remained approximately the same, so that the T 1r (F)-filter selection Figure 9. Fluorine-19 spectra (centreband signals only) of two samples of PVDF, showing discrimination using a T 1r (H) filter.…”

Section: Applications To Fluoropolymersmentioning

confidence: 98%

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Selective NMR Pulse Sequences for the Study of Solid Hydrogen‐Containing Fluoropolymers

Ando

Harris

Hazendonk

et al. 2005

Macromol. Rapid Commun.

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Summary: Fluorine‐19 NMR spectra of solids have some special features, which are discussed in this article. In particular, they generally contain two abundant spin baths (protons and fluorine nuclei). This situation throws up some special operational requirements, as does the study of heterogeneous samples. The relaxation characteristics of heterogeneous systems, which are briefly described herein, frequently permit the use of specific pulse sequences to obtain subspectra for individual components. Various possible selective sequences for use in fluorinated heterogeneous organic solids are listed and their actions rationalized on the basis of molecular mobility. Semicrystalline hydrogen‐containing fluoropolymers form especially suitable systems for such operations, and in order to understand their domain structures it is essential to obtain subspectra of the amorphous and crystalline domains. Examples are given of the use of selective pulse sequences for studying fluoropolymers, especially for poly(vinylidene fluoride) (PVDF) and the copolymer P(VDF75/TrFE25) (TrFE = trifluoroethylene).

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Section: Applications To Fluoropolymersmentioning

confidence: 77%

Section: Applications To Fluoropolymersmentioning

confidence: 98%

Selective NMR Pulse Sequences for the Study of Solid Hydrogen‐Containing Fluoropolymers

Ando

Harris

Hazendonk

et al. 2005

Macromol. Rapid Commun.

Self Cite

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“…This situation is similar to the PVDF homopolymer. 12 In addition, the amorphous selective spectra obtained using the delayed CP pulse sequence, both with and without spin-locking (t SL ¼ 0 and 5ms), are shown in Figure 2b. The intensities of the broad crystalline signals in Figure 2a (top; i.e., 2 LT and 8 LT ) were significantly reduced in Figure 2b.…”

Section: Resultsmentioning

confidence: 99%

“…This situation is similar to the PVDF homopolymer. 12 In addition, the amorphous selective spectra obtained using the delayed CP pulse sequence, both with and without spin-locking (t SL ¼ 0 and 5ms), are shown in Figure 2b F values obtained by fitting the decays using either a single-or double-exponential function were incorporated into the figure. As peak 1 am overlapped the remnant of the crystalline signals, two relaxing components were observed with the longer component containing the spin diffusion from the crystalline to the amorphous domains.…”

Section: Resultsmentioning

confidence: 99%

“…Solid-state NMR enables us to selectively observe either the amorphous or crystalline domains by applying the appropriate pulse sequences. [11][12][13] Using these techniques, we used variable temperature (VT) 19 F MAS NMR measurements to analyze the heating and cooling processes for a semi-crystalline P(VDF 75 /TrFE 25 ) system containing a significant amorphous domain.…”

Section: Introductionmentioning

confidence: 99%

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Solid-state 19F MAS and 1H→19F CP/MAS NMR study of the phase-transition behavior of vinylidene fluoride–trifluoroethylene copolymers: 2. semi-crystalline films of VDF 75% copolymer

Aimi

Ando

2012

Polym J

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The changes in the crystalline structure and molecular mobility in the semi-crystalline vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer P(VDF 75 /TrFE 25 ) caused by the ferroelectric-paraelectric phase transition were analyzed using variable temperature solid-state 19 F magic angle spinning (MAS) and 1 H-19 F cross polarization/MAS nuclear magnetic resonance spectroscopy in the temperature range of 42-129 1C. The conformational exchange between trans and gauche at the VDF and VDF-TrFE head-to-head linkage gradually increases at temperatures above 77 1C, and the conformational exchange at the head-to-tail linkage has a key role in the ferroelectric-paraelectric phase transition. The anomalous decrease in the amorphous peak intensities and the presence of a T 1q F value similar to that of the crystalline domain at 122 1C indicate that cooperative motion occurs in both phases just above the transition temperature (T c ). The amorphous domain is assimilated by the crystalline domain upon lowering the temperature from 129 to 85 1C, which significantly increases the crystallinity to below T c , as indicated by the shape of the spectra, and identical T 1q INTRODUCTIONVinylidene fluoride (VDF)-trifluoroethylene (TrFE) copolymer (P(VDF x /TrFE 1 Àx )), where x is the VDF molar fraction, is a typical ferroelectric polymer that shows a ferroelectric-paraelectric phase transition, which has garnered much interest in the effort to clarify its mechanism. 1,2 Two types of ferroelectric phases have been reported at room temperature, that is, the low-temperature (LT) and the cooled phase, depending on the VDF content and preparation conditions of the copolymer. 2 In the LT phase, the CF 2 dipoles are arranged in parallel because of the planar zigzag formed by the all-trans polymer chains, which is the same arrangement as the PVDF form I (b-form), whereas in the cooled phase, long trans segments are connected by irregular trans-gauche linkages along their chain axis to form a type of super lattice. However, the stable crystal structure in the hightemperature (paraelectric) phase is hexagonal and is composed of statistically mixed chains with TG þ , TG -, T 3 G þ and T 3 Gconformations. These chains rotate about their axes via the onedimensional diffusion of the conformational defects along the chain.Several reports have shown that lamellar crystals grow in P(VDF/ TrFE) films at VDF contents of x ¼ 0.60 to 0.82 when annealed at temperatures above the Curie point (T c ). In particular, annealing such polymers at elevated temperatures in the paraelectric phase increases the integrated X-ray diffraction intensities of the 110 and 200 reflections, which correspond to the all-trans chains, and sharpen the differential scanning calorimetry (DSC) endotherms observed at T c . [3][4][5][6][7] The efficient growth of lamellar crystals in the paraelectric phase has been explained using a sliding diffusion model for the polymer chains. For instance, a polyethylene lamellar crystal can thicken at higher pressures through th...

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Application of SSNMR to Selected Classes of Systems

2021

Solid State NMR

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Fluorine-19 solid-state NMR investigation of regiodefective semicrystalline α-poly(vinylidenefluoride)

Cited by 25 publications

References 33 publications

Selective NMR Pulse Sequences for the Study of Solid Hydrogen‐Containing Fluoropolymers

Selective NMR Pulse Sequences for the Study of Solid Hydrogen‐Containing Fluoropolymers

Solid-state 19F MAS and 1H→19F CP/MAS NMR study of the phase-transition behavior of vinylidene fluoride–trifluoroethylene copolymers: 2. semi-crystalline films of VDF 75% copolymer

Application of SSNMR to Selected Classes of Systems

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