P-PVDF

Immobilon-P PVDF membrane, 0.45-pm pore size (Mil-lipore, Catalog IPVH 000 10)... 

All sample proteins were run on either 12% or 14% pre-cast Novex 1.0 mm, 10 well gels under non-reducing conditions according to Laemmli (7). Samples were immediately electroblotted to Immobilon-P PVDF membrane using a semi-dry (MilliBlot-SDE) electroblotter essentially quantitiatively (8). After blotting, PVDF was washed briefly in HPLC water and stained with 0.05% Brilliant Blue-G Coomassie (BB-G) /20% methanol /0.5% acetic acid or Amido Black (2). The membrane was kept wet and not allowed to dry (9). Enzymatic digestion was performed as described (2) with all digestion and extraction buffer volumes reduced to 25 pL. 

Comparative HPLC peptide maps of transferrin and myoglobin were used to evaluate relative yields of tryptic peptides from different types of blotting membranes. To ensure identical transfer conditions, replicate lanes from a single gel were transferred to side-by-side strips of nitrocellulose, Immobilon P PVDF and Trans-Blot PVDF as described in Methods. As shown in Fig. 1, our results confirm the observations of Fernandez et al. (15) that optimal... 

Figure 20. Left real permittivity (full symbols) and loss factor (open symbols) obtained in a P-PVDF film at different fiequencies (see labels inside the graphics) (data adapted from [170]). Right Dynamic mechanical spectra of a p-PVDF film obtained at a frequency of 1 Hz, in tensile mode, performed along ftie longitudinal (solid lines) and transverse (dashed lines) directions, with respect to the stretch direction used to process the film (data adapted from [171]).

R. S.C. Monkhouse, P.D. Wilcox and P. Cawley, Flexible Interdigital PVDF transducer for the generation of lamb waves in structures. Ultrasonics (in press). 

Unlike other synthetic polymers, PVDF has a wealth of polymorphs at least four chain conformations are known and a fifth has been suggested (119). The four known distinct forms or phases are alpha (II), beta (I), gamma (III), and delta (IV). The most common a-phase is the trans-gauche (tgtg ) chain conformation placing hydrogen and fluorine atoms alternately on each side of the chain (120,121). It forms during polymerization and crystallizes from the melt at all temperatures (122,123). The other forms have also been well characterized (124—128). The density of the a polymorph crystals is 1.92 g/cm and that of the P polymorph crystals 1.97 g/cm (129) the density of amorphous PVDF is 1.68 g/cm (130). 

Relaxations of a-PVDF have been investigated by various methods including dielectric, dynamic mechanical, nmr, dilatometric, and piezoelectric and reviewed (3). Significant relaxation ranges are seen in the loss-modulus curve of the dynamic mechanical spectmm for a-PVDF at about 100°C (a ), 50°C (a ), —38° C (P), and —70° C (y). PVDF relaxation temperatures are rather complex because the behavior of PVDF varies with thermal or mechanical history and with the testing methodology (131). 

Copolymer compositions differ from PVDF in that the crystalline P phase is obtained without mechanical deformation. Thus, various thicknesses of the material can be readily produced. Unfortunately, a reproducible copolymer is not yet commercially available. 

In this work, the response of PVDF is studied in a cooperative effort with Francois Bauer of the Institut Saint Louis, France, L.M. Lee of the Ktech Corporation of Albuquerque, New Mexico, and M.U. Anderson, R.P. Reed, and L.M. Moore of Sandia National Laboratories. The basis of the work is... 

For PVDF, several experiments have shown that at room temperature the p form is thermodynamically the most stable, while the ot form is kinetically the most advantageous. For instance, by solution crystallization (casting from polar hexamethylphosphamide solutions) p form, y form and a form crystals are obtained for low, intermediate and high evaporation rates, respectively [15, 66]. 

Particularly relevant is the case of some copolymers of PVDF. Already small amounts (5-20% by mol) of a fluorolefinic comonomer (vinyl fluoride (VF) [89-90], trifluoroethylene [91-93], tetrafluorethylene [94, 95]) can force the polymers to a melt crystallization in the piezoelectric P form. (We recall that the homopolymer crystallizes in the non-piezoelectric a form, by melt crystallization). 

Just as an example, the X-ray diffraction patterns of compression moulded samples of PVDF, poly(vinylfluoride), and of some VDF-VF copolymers of different compositions are shown in Fig. 17 [90]. The degrees of crystallinity of the copolymer samples (40-50%) are high and analogous to those of the homopolymer samples. This indicates a nearly perfect isomorphism between the VF and VDF monomeric units [90, 96], The diffraction patterns and the crystal structures of the copolymers are similar to those of PVF, which are in turn similar to the X-ray pattern and crystalline structure of the P form of PVDF. On the contrary, the X-ray pattern of a PVDF sample crystallized under the same conditions (Fig. 17 a) is completely different, that is typical of the non-piezoelectric a form [90]. 

We have already cited (Sect. 4.1) that a small amount of suitable comonomeric units in PVDF allows to obtain the piezoelectric p form using normal melt processing conditions, without a significant reduction of the degree of crystallinity. This is the main reason for the recent commercial development of the VDF-trifluorethylene copolymers [121]. 

Figure 15. KFM images obtained from the PVDF-bonded composite made from (a) the as-received SFG50 graphite and from (b) the surface-modified SFG50 graphite. Reprinted from S.-B. Lee and S.-I. Pyun, Determination of the morphology of surface groups formed and PVDF-binder materials dispersed on graphite composite electrodes in terms of fractal geometry, J Electroanal. Chem. 556, p. 75, Copyright 2003, with permission from Elsevier Science.

Mokrini, A., Huneault, M. A. and Gerard, P. 2006. Partially fluorinated proton exchange membranes based on PVDF-SEBS blends compatibilized with methylmethacrylate block copolymers. Journal of Membrane Science 283 74—83. 

This section will successively deal with the treatment of PTFE, the treatment of PVDF and the treatment of P(VDF-HFP) copolymers. 

Fig. 11. Comparison of PVDF (a) and P (VDF-HFP) (b) surface respective morphoiogies as shown by scanning eiectron microscopy.

P. Marmey, M.C. Porte-Durrieu, C. Baquey, PVDF multifilament yarns grafted with polystyrene induced by gamma-irradiation Influence of the grafting parameters on the mechanical properties, Nucl. Instrum. Methods Phys. Res. B 208 (2003) 429-435. 

In the P phase of polyvinylene fluoride (PVDF), the CF2 groups in a polymer chain are all pointing in the same direction (Figure 9.20), so that a dipole moment... 

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