Vinylidene polymers

Vinylidene polymers Vinylidine chloride Vinyl interlayer Vinylite flooring Vinyl ketal polymers Vinyllithium [917-57-7]... 

VINYLIDENE POLYMERS, POLY(VINYLIDENE FLUORIDE) ELASTOMERS. 

Some polymers like PE and NR get cross-linked on exposure to radiation while others like those based on vinylidene polymers, e.g., polymethylmethacrylate (PMMA), polyisobutylene, degrade. Certain other types of polymer stmctures (high aromatic content or thermoset) resist degradation by high-energy radiation. Coating polymers usually contain acrylic, methacryUc, or fumaric vinyl unsaturation along or attached to the backbone. 

The microstructural approach can be extended to the polymers of 1,2-disub-stituted ethylenes, to diene polymers, and to those obtained by ring-opening polymerization and by polycondensation. Differences with regard to vinyl and vinylidene polymers are observed in the type and number of the sequences, their nomenclature and the statistic model for the quantitative interpretation of their distribution. 

The first point of the stereochemical analysis is in the recognition of the sequence to which a given nucleus is sensitive the problem seems rather obvious for vinyl or vinylidene polymers where the sequence must extend equally from the two sides of the nucleus in question but for diene polymers or those containing heteroatoms, the problem is not so simple. In the present case, the methylene protons are sensitive to the structure of the even sequences, dyads and tetrads, whereas the methyl protons are sensitive to the odd sequences, triads, and pentads. 

The photo-cross-linkability of a polymer depends not only on its chemical structure, but also on its molecular weight and the ordering of the polymer segments. Vinyl polymers, such as PE, PP, polystyrene, polyacrylates, and PVC, predominantly cross-link, whereas vinylidene polymers (polyisobutylene, poly-2-methylstyrene, polymethacrylates, and poly vinylidene chloride) tend to degrade. Likewise, polymers formed from diene monomers and linear condensation products, such as polyesters and polyamides, cross-link easily, whereas cellulose and cellulose derivatives degrade easily. ... 

Section 7.2.2). This feature makes it unique among vinylidene polymers, which typically are degraded by high-energy radiation.74... 

A new method is proposed for the estimation of the segmental orientation of vinyl or vinylidene polymers of moderate crystallinity by acquisition of only one Raman spectrum at a specific polarisation geometry. Data are presented for PVC, isotactic PP, and PVDF. 21 refs. 

Direct chlorination of vinyl chloride generates 1,1,2-tnchloroethane [79-00-5] from which vinylidene chloride required for vinylidene polymers is produced. Hydrochlorination of vinylidene chloride produces 1,1,1-trichloroethane [71-55-6], which is a commercially important solvent. Trichloroethylene and perchloroethylene are manufactured by chlorination, hydrochlorination, or oxychlorination reactions involving ethylene. Aromatic solvents or pesticides such as monochlorobenzene, dichlorobenzene, and hexachlorobenzene are produced by reaction of chlorine with benzene. Monochlorobenzene is an intermediate in the manufacture of phenol, insecticide DDT, aniline, and dyes (see Chlorocarbons a>td Chlorohydrocarbons.)... 

Polymerization of nonsymmetrical cyclic molecules gives stereochemi-cally variable polymers, [-SiRR 0-] , analogous to the totally organic vinyl and vinylidene polymers [-CRR CH2-] . In principle, these polymers can be prepared in the same stereoregular forms (isotactic and syndiotactic) that have been achieved for some of their organic counterparts 1, 17). Unfortunately, the stereoregular forms have not been prepared, and only the stereoirregular form (atactic) has been obtained. Unlike the other two stereochemical forms, the atactic form is inherently noncrystallizable. 

Similar to vinyl derivatives, a number of substituted vinylidene polymers are used in practice. Some of these polymers are part of classes of polymers such as halogenated polyolefins and were discussed separately (see Section 6.3 and 7.5). One example of polymer that can be indicated here is poly(vinylidene cyanide). Its pyrolysis generates a high yield of monomer [42],... 

The resulting polymer has a carbon chain backbone, but it is different from common vinyl or vinylidene polymers. 

Vinyl polymers of the type CH2CHX and vinylidene polymers of the type CH2CXY are capable of existing in different stereoregular forms. These are generally referred to as isotactic, syndiotactic, and atactic forms it is here assumed that the reader is familiar with this nomenclature and the specific structures associated with it. It has been shown that steric isomerism has little effect on the Tg of vinyl polymers but profoundly affects the Tg of vinylidene polymers.12 In the latter case, the isotactic form invariably is associated with the lowest Tg values. This result has also been rationalized on the basis of the Gibbs-DiMarzio theory, but again the details are beyond the scope of this book. 

Polyethylene is a special example of a generic class that includes many of the industrially important macromolecules, the vinyl and vinylidene polymers. The chemical repeat unit of a vinylidene polymer is -fCH2—CXY where X and Y represent single atoms or chemical groups. For a vinyl polymer Y is H and for polyethylene both X and Y are H. If X is —CH3, Cl, —CN, — or 0(C=0)CH3, where represents the mono-substituted benzene ring, or phenyl group, and Y is H, the well-known materials polypropylene, poly(vinyl chloride) (PVC), polyacrylonitrile, polystyrene and poly(vinyl acetate), respectively, are obtained. 

ACRONYM. TRADE NAME PHEMA, Hydron CLASS Vinylidene polymers... 

ACRONYM PMAA, PMA CLASS Vinylidene polymers STRUCTURE H CH3... 

ACRONYMS, TRADE NAMES PVDF, PVF2, Kynar, Solef, Neoflon, Foraflon, KF, Soltex CLASS Vinylidene polymers STRUaURE -(CH2Cp2)n-... 

Uses Intermediate in prod, of vinylidene polymer plastics such as flexible film, food wrap, pkg. materials, Saran prod, of flame-retardant coatings for fiber/carpet backings piping coating for steel pipes comonomer for nitrile rubber paints adhesives syn. fibers solvent in pharmaceuticals... 

Figure 1.15 shows polyisobutylene, a vinylidene polymer with symmetric substitution, and thus without stereoisomers. Cis and trans isomers are possible in butenylene polymers. Two examples are at the bottom of Fig. 1.15. They are not interconvertable by rotating of the molecule. Shown in the figures are the trans isomers (). In the cis isomers the backbone chain continues on the same side of the double bond ( /). In Figs. 1.16 and 1.17 a series of vinyl and vinylidene polymers are shown. The above-mentioned PTFE, poly(vinyl butyral), and poly (methyl methacrylate) are given, starting in Fig. 1.17. Polyoxides are drawn at the bottom of Fig. 1.17, and the top of Fig. 1.18. Poly(ethylene terephthalate) and two aliphatic polyamides (nylon 6,6 and nylon 6) round out Fig. 1.18. The 20 polymers just looked at should serve as an initial list that must be extended many-fold during the course of study of thermal analysis of polymeric materials.

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