Vinylidene fluoride synthesis

Uses Synthetic fibers and adhesives chemical intermediate in vinylidene fluoride synthesis production of poly(vinyl dichloroethylene) and LLl trichloroethane comonomer for food packaging, coating resins, and modacrylic fibers. 

Yang, Y. S., Shi, Z. Q. and Holdcroft, S. 2004. Synthesis of poly[arylene ether sulfone-b-vinylidene fluoride] block copolymers. European Polymer Journal 40 531-541. 

The compilation of such data constituted a firm basis that was used to study a specific and more complicated system the elucidation of the electronic structure of a copolymer of ethylene (48%) and tetrafluoroethylene (52%) whose synthesis was conducted in order to maximize the alternating sequences. The valence band spectrum of such a compound (Figure 8) was found very similar to the one measured e.g. for poly(vinylidene fluoride). But, by looking to the fine details of the spectrum, by simulating the valence band of a block copolymer (by addition of PE and PTFE spectra), and by comparison with model calculations, it was possible to show that the C-C band width and the distance F2s-top of the C-C band were characteristic of an ethylene-tetrafluoro-ethylene copolymer with dominant alternant structure (28). 

The matter of the head-to-head, tail-to-tail polymerization of vinyl fluoride, vinylidene fluoride, and trifluoroethylene and the copolymerization of vinyl fluoride with vinylidene chlorofluoride and l-chloro-2-fluoroethylene has been extensively studied by Cais and Kometani [24-27] and by Bruch, Bovey, and Cais [28]. The synthesis of pure head-to-tail poly(trifluoroethylenes) is described in Ref. [25]. Isomers of poly(vinyl fluoride) with controlled regiosequence microstructure are discussed in Ref. [27]. 

PVDF is correctly named poly(l,l-difluoroethylene) and represented by (-CF2CH2-)n- It is a hard, tough thermoplastic fluoropolymer. PVDF is prepared by free-radical initiated polymerization, either in suspension or (usually) in emulsion systems. The basic raw material for PVDF is vinylidene fluoride (CH2=CF2), a preferred synthesis of which is dehydrochlorination of chlorodifluoroethane. 

PVDF film, as produced from the melt, is largely in the nonpolar a-form, the fS phase only being obtained after subsequent processing operations, as described above. If however, vinylidene fluoride is copolymerized with as little as 7% by weight of trifluoroethylene, a copolymer is formed with crystallites completely in the / -form. This obviates the need for stretching after synthesis and the copolymer can be processed byway conventional routes, such as injection molding. Moreover, unlike PVDF, copolymers of vinylidene fluoride and trifluoroethylene have been shown to demonstrate the ferroelectric to paraelectric transition. For a copolymer with a composition of 55% vinylidene fluoride and 45% trifluoroethylene, a phase transition is observed near 70°C, and with 90% vinylidene difluoride, a phase transition at 130°C. 

Liao, C., Zhao, J., Yu, R, Tong, H., and Luo, Y. 2012. Synthesis and characterization of low content of different SiO materials composite poly(vinylidene fluoride) ultrafiltration membranes. ZleraZinafiow 285 117-122. 

A.M. Dessouki, N.H. Taher, M.B. El Arnaouty, Synthesis of permselective membrane induced grafting of N-vinyl-pyrrolidone onto poly(tetraffuoroethy-lene-hexaftuoropropylene-vinylidene fluoride) (TFB) films. Polymer International 48 (1999) 92, 67. 

Ogoshi, T., Chujo, Y., (2005) Synthesis of poly(vinylidene fluoride) (PVdF)/silica hybrids having interpenetrating polymer network structure by using crystallization between PVdF chains. Polymer Science Part A, Polymer Chemistry, Vol. 43, No. 16, pp. 3543-3550, ISSN 1099-0518. 

Difluoro-l-chloroethane (obtained from acetylene, vinylidene chloride or 1,1,1-trichloroethane) is mostly used as the starting material for the synthesis of vinylidene fluoride ... 

Recently, also the synthesis of VF2 from 1,1-difluorethane on contact with Cr203/ AI2O3 based catalysts in the presence of oxygen has been reported [527]. Vinylidene fluoride is usually stored and shipped without polymerization inhibitors. If desired, terpenes or quinones can be added to inhibit polymerization. Before use the monomer has to be distilled and degassed several times to remove impurities [528]. Since vinylidene fluoride is a gas under normal conditions, most of the polymerization processes are carried out under pressure. The advantage of poly(vinylidene fluoride) is its good solubility in solvents such as dimethylacetamide (DMA), dimethylformamide (DMF), or dimethyl sulfoxide (DMSO). This fact allows its commercial processing without any problems. Industrially, polymerization is usually accomplished in suspension or emulsion as described in several patents [529-533]. Vinylidene fluoride can also be polymerized with... 

SCHEME 12.4 Synthesis of poly(vinylidene fluoride)-5-sulfonated polystyrene. 

---