Vinyl bromide polymerization

One of the first methods of polymerizing vinyl monomers was to expose the monomer to sunlight. In 1845, Blyth and Hoffman [7] obtained by this means a clear glassy polymeric product from styrene. Berthelot and Gaudechon [8] were the first to polymerize ethylene to a solid form and they used ultraviolet (UV) light for this purpose. The first demonstration of the chain reaction nature of photoinitiation of vinyl polymerization was done by Ostromislenski in 1912 [9]. He showed that the amount of poly(vinyl bromide) produced was considerably in excess of that produced for an ordinary chemical reaction. 

A very useful three-carbon olefin is acrolein dimethyl acetal (5). Acrolein itself cannot be used because it polymerizes and/or reacts with amines under the normal reaction conditions. With piperidine or morpholine as the base, acrolein acetals react in good yield with a wide variety of vinylic bromides to give dienal acetals and/or ami-noenal acetals. These product mixtures, after being treated with excess aqueous oxalic acid and being steam distilled, yield E,E-conjugated dienals, usually in good yields. Methacrolein acetals and 3-buten-2-one ethylene ketal also react well, but the crotonaldehyde acetals do not. 

Oxidants. The highly flammable gas reacts violently with oxidants. Sunlight. Vinyl bromide may polymerize in sunlight.2... 

It has been reported that reaction of n. 3-unsatu rated carboxylic acids with bis(collidine)bromine(l) hexafluorophos-phate leads to the formation of 2-oxetanones in moderate yields (Equation 33) <1999JOC81>. As with the related reaction of cinnamyl alcohols (discussed in Section 2.05.9.1), this 4- electrophilic intermediate. The cyclization reaction was diastereospecific single (E)- or (Z)-isomers were reacted to give single stereoisomeric products. Lactonization was favored by substrates that were /3-dialkyl-substituted, or ct-alkyl/aryl-, /3-aryl-substituted on the C-C double bond. ct-Monoalkyl/aryl, /3-unsubstituted substrates gave either polymeric products or exclusive vinyl bromide formation. 

Copolymers of vinyl chloride-vinyl bromide were prepared in bulk using the same conditions in the preparation of PVC, except that only uranyl nitrate was used as in initiator with visible light to avoid photodegradation during polymerization. Thermal analysis of the copolymer indicated random placement of the two comonomers. 

Table 2 shows also that polymerized vinyl bromide has a C—Br bond which is even less stable than the main chain C—C bond in PAN (257 versus 297 kJ/mol, if the data of the same author are compared). Hence it may be anticipated that the CN oligomerization can be started at lower temperature with AN/VBr copolymers, with the additional advantage of no main chain scission taking place in this step. 

In vinyl compound polymerization of vinyl acetate, alcohol, bromide, chloride, or carbonate, ascorbic acid can be a component of the polymerization mixture (733-749). Activators for the polymerization have been acriflavine (734), other photosensitive dye compounds (737,738), hydrogen peroxides (740,741,742), potassium peroxydisulfate (743), ferrous sulfate, and acyl sulfonyl peroxides (747). Nagabhooshanam and Santappa (748) reported on dye sensitized photopolymerization of vinyl monomers in the presence of ascorbic acid-sodium hydrogen orthophosphate complex. Another combination is vinyl chloride with cyclo-hexanesulfonyl acetyl peroxide with ascorbic acid, iron sulfate, and an alcohol (749). Use of low temperature conditions in emulsion polymerization, with ascorbic acid, is mentioned (750,751). Clarity of color is important and impact-resistant, clear, moldable polyvinyl chloride can be prepared with ascorbic acid as an acid catalyst (752) in the formulation. 

Halogenated polyolefins form another class of polymers. Some of the polymers from this class have important practical applications. Among these are poly(vinyl chloride), poly(vinylidene chloride), and polytetrafluoroethylene. Several unusual polymers such as poly(vinyl bromide) also are included in this class. Most halogenated polymers are obtained by the polymerization of a halogenated monomer. However, chemical modification (e.g. chlorination) of a preexistent polymer also can be applied to obtain partially halogenated materials. 

NH, NH-, -CN), silicon and olefinic double bonds are more polymerizable while those containing oxygen (e.g. -C=0,-0-,-0H), chlorine, aliphatic hydrocarbon and cyclic hydrocarbons tend to decompose. Brown (13) reported in his studies of a series of vinyl halides that the dihaloethylenes polymerize more rapidly than the corresponding monohalides and that chlorides and bromides polymerize more rapidly than the fluorides. Kobayashi, et. al. (IJ) found that the additons of certain halo-genated compounds to hydrocarbon monomer streams often dramatically increases the polymerization rate. Thus, these halogenated compounds may be considered to act as gas phase catalysts for the plasma polymerization of hydrocarbons. 

What is fhe implication of our work wifh respect to the metal-catalyzed polymerization of polar vinyl monomers FirsL for fhe late metal compounds, fhe polar vinyl monomers can clearly outcompete efhene and simple 1-alkenes wifh respect to insertion. However, fhe ground-state destabilization of the alkene complex that favors the migratory insertion of fhe polar vinyl monomers is a two-edged sword because it biases the alkene coordination towards ethene and l-alkenes. Indeed, we have observed fhe near quantitative displacement of vinyl bromide by propene to form 7 from 3 (Scheme 9.1). Thus, the extent of incorporation of fhe polar vinyl monomer in fhe polymer will depend on the opposing trends in alkene coordination and migratory insertion. The above discussion does not take into account the problem of functional group coordination for acrylates or halide abstraction for vinyl hahdes. 

The projected palladium-catalyzed cross-coupling required the availability of vinylstannane 216. As shown in Scheme XXV, the preparation of this lactone was initiated by copper-catalyzed 1,4-addition of l-(trimethylsilyl)vinylmagne-sium bromide to 5(2//)-furanone (212). For this process to be successful, excess trimethylsilyl chloride had to be present from the outset in order to trap the enolate as it was formed and circumvent its polymerization. This modification gave rise to C-silylated lactone 213, which was chemoselectively desilylated and transformed via vinyl bromide 215 [120] into stannane 216. 

Small amounts of vinyl bromide can be obtained readily in the laboratory by the action of alcoholic KOH or NaOH on 1,2-dibromoethane.223 224 1,1-Dibromoethane is formed from acetaldehyde and PCl3Br2.228 As stabiliser against polymerization 0.1-0.2% of hydro-quinone is added to vinyl bromide phenol is added to vinyl chloride (b.p. —13.9°). 

It is a liquid of ethereal odor, which boils at 16°, and has the specific gravity 1.517 at 14°. It is polymerized by the action of sunlight into a white mass which is insoluble in alcohol and ether. It shows but few of the reactions which are characteristic of the saturated halogen compounds. When treated with an aqueous solution of an alkali, an alcohol is not formed sodium ethylate does not yield an ether, nor sodium acetate an ester. With all these reagents vinyl bromide loses hydrogen bromide and acetylene is formed —... 

Polyacrylonitrile fibres can be flame-retarded by vinylidene chloride, vinyl chloride, or vinyl bromide added in the course of polymerization. Some attempts were made with red phosphorus as well. ... 

In 1860, Hofman described the "metamorphosis" of vinyl bromide to pol3winyl bromide and Baumann repeated this "conversion" with vinyl chloride in 1872. However, polyvinyl chloride (PVC) was not patented until 1912, when Klatte used sunlight to initiate the polymerization of vinyl chloride. Klatte produced the monomer by the mercuric chloride catalyzed addition of HCl to acetylene. He also suggested the use of camphor and triphenyl phosphate as plasticizers for PVC. 

Fig. 2. Phase diagram for the polyelectrolyhe complex formed by poly(Af-ethyl-4-vinyl-pyridinium bromide) (polymerization degree 530) and poly(methacrylic acid) (polymerization degree 1830). The dots (represent pH values at which the turbidity of the polymer solutions was first observed at 470 nm. Ionic strength was 0.01 M NaCl (a), 0.1 M NaCl (b), 0.25 M NaCl (c), and 0.5 M NaCl (d). Dashed area represents pH/composition range where the complex is insoluble. Reproduced from Ref 11 with permission.

Assandei and Percec reported that the in situ formed complex (Fe-34) from Fe(0) and o-phenanthroline induced the polymerization of vinyl chloride when employed with appropriate bromide initiators. Though the polymerization ceased around 40%, moderate and MWDs (Mw/Mn 1.5) were obtained for the vinyl chloride polymerization by metal catalysts for the first time. For the polymerization of stearyl methacrylate, a trivalent [Fe(DMF)6](C104)3 with bipyridine (Fe-35) was employed in conjimction with either AIBN or AlBN/CBr4. Though the details were imclear, a linearly increasing M with moderate MWDs was observed. 

Gathers and Fuoss have shown that the conductance of poly-(4-vinyl-N-butylpyridinium bromide) increases with the dielectric constant of the medium. The energy of removal of a mobile bromide ion from the electrostatic field of the molecule decreases as the dielectric constant is increased hence the number of free ions and the net charge on the polymeric ion should increase. Both contribute toward increasing the conductance. ... 

The addition of a large excess of bis(cj-alkenyl)zinc compounds to the TiC -catalyzed polymerization of propene resulted in an increased polymer yield, but a reduction in the molecular weights of the polymers.64 This suggests that the diorganozinc compounds are both co-catalysts and chain-transfer agents in this polymerization. The catalyst activity decreased in the order bis(3-butenyl)zinc < bis(7-octenyl)zinc < chlorodiethylaluminum. Bis(7-octenyl)zinc was co-polymerized with propene to afford hexylzinc side chains, whose zinc-carbon moieties were converted to vinyl groups by the addition of allyl bromide. 

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