Vinylidine chloride, polymerization

Composites of polypyrrole and poly(vinyl chloride) have been prepared by several groups (64-67). Polythiophene-poly(vinyl chloride) composites have also been prepared (68). The electropolymerization of pyrrole on poly(vinyl chloride)-coated electrodes yielded composites with mechanical properties (tensile strength, percent elongation at break, percent elongation at yield) similar to poly(vinyl chloride) (65) but with a conductivity of 5-50 S/cm, which is only slightly inferior to polypyrrole (30-60 S/cm) prepared under similar conditions. In addition, the environmental stability was enhanced. Morphological studies (69) showed that the polypyrrole was not uniformly distributed in the film and had polypyrrole-rich layers next to the electrode. Similarly, poly(vinyl alcohol) (70) poly[(vinylidine chloride)-co-(trifluoroethylene)] (69) and brominated poly(vinyl carbazole) (71) have been used as the matrix polymers. The chemical polymerization of pyrrole in a poly(vinyl alcohol) matrix by ferric chloride and potassium ferricyanide also yielded conducting composites with conductivities of 10 S/cm (72-74). 

VINYLIDENE CHLORIDE or VINYLIDENE CHLORIDE(II) or VINYLIDINE CHLORIDE MONOMER (75-35-4) Forms explosive mixture with air (—18°F/—28°C). Inhibitors such as the monomethyl ether or hydroquinone must be added to prevent polymerization. Readily forms explosive peroxides with air or contaminants (a white deposit may indicate the presence of explodable peroxides). Violent polymerization from heat or on contact with oxidizers, chlorosulfonic acid, nitric acid, or oleum or under the influence of oxygen, sunlight, copper, or aluminum. Violent reaction with alkali metals (lithium, sodium. 

Polymerizations in thiourea canal complexes yield high melting crystalline rra/w-1,4-polybutadiene, 2,3-dimethylbutadiene, 2,3-dichlorobutadiene, and 1,3-cyclohexadiene. Cyclo-hexadiene monoxide, vinyl chloride, and acrylonitrile also form stereoregular polymers. On the other hand, polymerizations of isobutylene and of vinylidine chloride fail to yield stereospecific polymers. 

If the polymer is insoluble, it precipitates out without any noticeable increase in solution viscosity. Examples of this type of reaction can be polymerizations of acrylonitrile or vinylidine chloride. The activation energy is still similar to polymerizations of soluble polymers and the initial rates are proportional to the square root of initiator concentration. Also, the molecular weights of the polymerization products are inversely proportional to the polymerization temperatures and to initiator concentrations. Furthermore, the molecular weights of the resultant polymers far exceed the solubility limits of the polymers in the monomers. The limits of acrylonitrile solubility in the monomer are at a molecular weight of 10,000. Yet, polymers with molecular weights as high as 1,000,000 are obtained by this process. This means that the polymerizations must proceed in the precipitated polymer particles, swollen and surrounded by monomer molecules. 

Poly(vinylidine chloride) can be formed in bulk, solution, suspension, and emulsion polymerization processes. The products are highly crystalline with regular structures and a melting point of 220 °C. The structure can be illustrated as follows ... 

Vinylidine chloride homopolymers form readily by free-radical polymerization, but lack sufficient thermal stability for commercial use. Copolymers, however, with small amotmts of comonomers find many applications. 

The rates of thermal decompositions of poly(vinylidine chloride)s were shown to depend upon the method by which the polymers were prepared [497]. Those that were formed from very pure monomers by mass polymerization are most stable. Polymers prepared by emulsion polymerizatiOTi, on the other hand, degrade fastest. The mechanism of degradation of poly(vinylidine chloride) was proposed to be as follows [498-500] ... 

Another widely used approach is the in situ polymerization of an intractable polymer such as polypyrrole onto a polymer matrix with some degree of processibil-ity. Bjorklund [30] reported the formation of polypyrrole on methylcellulose and studied the kinetics of the in situ polymerization. Likewise, Gregory et al. [31] reported that conductive fabrics can be prepared by the in situ polymerization of either pyrrole or aniline onto textile substrates. The fabrics obtained by this process maintain the mechanical properties of the substrate and have reasonable surface conductivities. In situ polymerization of acetylene within swollen matrices such as polyethylene, polybutadiene, block copolymers of styrene and diene, and ethylene-propylene-diene terpolymers have also been investigated [32,33]. For example, when a stretched polyacetylene-polybutadiene composite prepared by this approach was iodine-doped, it had a conductivity of around 575 S/cm and excellent environmental stability due to the encapsulation of the ICP [34]. Likewise, composites of polypyrrole and polythiophene prepared by in situ polymerization in matrices such as poly(vinyl chloride), poly(vinyl alcohol), poly(vinylidine chloride-( o-trifluoroethylene), and brominated poly(vi-nyl carbazole) have also been reported. The conductivity of these composites can reach up to 60 S/cm when they are doped with appropriate species [10]. 

VINYLIDINE FLUORIDE (75-38-7) Flammable gas (flash point <-85°F/ < —65°C). Violent reaction with oxidizers, barium, sodium, or potassium. Reacts with aluminum chloride. Incompatible with hydrogen chloride. May form explosive compounds with light metals and metallic azides. Capable of forming unstable peroxides may cause explosive polymerization. Undergoes thermal decomposition when exposed to flame or red-hot surfaces. May accumulate static electricity, and cause ignition of its vapors. The uninhibited monomer vapor may block vents and confined spaces by forming a solid polymer material. 

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