Vinylidene group monomer

The transfer of a tertiary hydrogen between the polymer chain and a monomer can account for the vinylidene group in the polymer ... 

The vast majority of commercial polymers based on the vinyl group (H2C=CHX) or the vinylidene group (H2C=CX2) as the repeat unit are known by their source-based names. Thus, polyethylene is the name of the polymer synthesized from the monomer ethylene poly(vinyl chloride) from the monomer vinyl chloride, and poly(methyl methacrylate) from methyl methacrylate. 

The termination of the growing polymeric chain may occur through several different processes, mostly by chain transfer. Either the process of chain transfer with the monomer, or the reaction of dissociation to hydride, leads to the formation of terminal vinylidenic groups, whose presence was noticed in the olefin polymers, obtained with the previously described catalysts (22). 

Data on the significant role of the transfer reaction of the polymer chains with a monomer are in agreement with the number of vinyl and vinylidene groups in polyolefins 29.n8.n9)... 

This mechanism is in agreement with the presence of terminal vinylidene groups in polypropene [77], and the dependence of molecular weight on monomer concentration. 

Vinyl chloride has also been reacted with other monomers containing carboxyl, hydroxyl, acetate, maleate, and vinylidene groups. Some of these reactive groups permit cross-linking with other polymers such as alkyds and melamines. Typical solubility characteristics are shown in Figure 3. 

An IR spectroscopic technique for the study of kinetics of radical copolymerisation of acryl and vinyl monomers was developed. The technique is based on monitoring the conversion curves and determining copolymerisation rates in the course of the process separately for each monomer by measuring variations in the intensity of IR absorption bands of reacting vinylidene groups. A comparative study of the copolymerisation of model monomer pairs using monofunctional and polyfunctional compounds provided data on the role of structural-physical transformations, involved in the formation of crosslinked polymers, on the copolymerisation kinetics and on the non-uniformity of distribution of crosslinks in the copolymers formed. 17 refs. 

Because of the differences in reactivity between vinyl chloride and vinylidene chloride monomers, the structure of the copolymer was further investigated on the basis of the percentage of grouped monomers (i.e., the number average sequence length for vinyl chloride and vinylidene chloride repeat units). The results obtained were in excellent agreement with those obtained by PMR spectroscopy. 

Also, FEPM is a class of fluoroelastomers prepared from monomeric units containing one or more alkyl, perfluoroalkyl, or perfluoroalkoxy groups, with a reactive pendant group. This class of fluoroelastomers does not contain vinylidene fluoride monomer units. 

NMR spearoscopic end-group analysis confirmed this possible influence of silicon because of a high incorporation degree of the silane monomers as terminal vinylidene groups... 

This treatment can be extended without mrxlification to polymers obtained from vinylidene monomers with different substituents (CH2=CR R2) and from aldehydes (RCHO) in which the oxygen atom replaces the methylene group. 

Both P-hydride transfers result in polypropene molecules with one vinylidene and one n-propyl end group. The two transfers are zero- and first-order, respectively, in monomer. P-Hydride transfer yields vinyl end groups in ethylene polymerization. 

Moreover, we confirmed the results previously ascertained through radiochemical measurements. In fact, the comparison between such data and those obtained by IR measurements on the atactic polymer fraction (Table IV) shows that the ratio between the number of polymeric chains with a —C2H6 end group (corresponding to a chain transfer process depending on the catalyst concentration) and the number of polymeric chains with a vinylidenic end group of polymeric chains (corresponding to the chain transfer process with the monomer) is closely in accordance with the data reported in Fig. 33. 

Fluorocarbon elastomers represent the largest group of fluoroelastomers. They have carbon-to-carbon linkages in the polymer backbone and a varied amount of fluorine in the molecule. In general, they may consist of several types of monomers poly-vinylidene fluoride (VDF), hexafluoropropylene (HFP), trifluorochloroethylene (CTFE), polytetrafluoroethylene (TFE), perfluoromethylvinyl ether (PMVE), ethylene or propylene.212 Other types may contain other comonomers, e.g., 1,2,3,3,3-pentafluropropylene instead of HFP.213 Fluorocarbon elastomers exhibit good chemical and thermal stability and good resistance to oxidation. 

PDD as well as other dioxoles have been copolymerized with monomers such as vinyl fluoride, vinylidene fluoride, tiifluoroediylene, perfluoroalkylethylenes, chlorotrifluoroethylene, hexafluoropropylene, and perfluorovinyl ethers, some of which contain functional groups. 

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