Halogenated Monomers

There are mixed opinions on whether vinyl chloride will undergo alternating copolymerization with MA. Equimolar copolymers are claimed when various molar ratios of vinyl chloride and MA are combined and copolymerized in bulk or benzene at 50 C, with AIBN initiatorThe data showed that highest yields of copolymer occurred at polymerization of equimolar mixtures of the two monomers. Melville and Burnettestimate the copolymerization rate constant, at 25 C, is 1.2 x 10 liters moF s  

From three-component free-radical-initiated polymerization studies of ethylene, vinyl chloride, and MA, it was concluded that MA can undergo alternating copolymerization with vinyl chloride. Regardless of the initial monomer composition, a terpolymer was obtained with 50 mol % vinyl chloride and ethylene combined with 50 mol % MA. A CTC has been suggested to play a role in the copolymerization. However, the fact that 

In a different binary (vinyl chloride-MA) and ternary (vinyl chloride-MA-butadiene) copolymerization study, equimolar copolymerization of vinyl chloride and MA does not appear to be a general rule. The formation of equimolar copolymer appears restricted to limited cases, such as very low conversion and sufficiently high MA vinyl chloride ratios in the monomer feed. It is very hard to see how vinyl chloride, a weak acceptor, could become a donor monomer in the presence of the strong acceptor MA and a CTC formed from the monomer pair regulate copolymerization to obtain 1 1 alternating copolymer. The authors are inclined to agree with Ring s evaluation of this monomer pair. 

Allyl chloride, propenyl chloride isomers, trichloroethylene,l,3-dichloro-2-butene, 3-chloro-2-chloromethyl-1-propene, and chloroprene are all claimed to undergo alternating copolymerization with MA. Isopropenyl chloride is essentially nonpolymeriz-able by both free-radical and ionic initiators. However, mixtures of isopropenyl chloride and MA in benzene with AIBN, at 60°C, copolymerize quite readily to give colorless materials, with relatively high viscosities. The composition of the copolymers were found to be independent of monomer feed ratio and to consist essentially of a 1 1 composition of the monomer pair. In contrast, cis- and -propenyl chloride exhibit low copolymerization rates with MA and the resultant copolymers exhibit much lower specific viscosities than the isopropenyl chloride-co-MA polymers. 

It is well known that trichloroethylene will not undergo free-radical-initiated polymerization. However, MA and trichloroethylene have been copolymerized with free-radical initiators, both in bulk and solution, to obtain dark-colored materials. Kinetic studies showed the rate of copolymerization 

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For most vinyl polymers, head-to-tail addition is the dominant mode of addition. Variations from this generalization become more common for polymerizations which are carried out at higher temperatures. Head-to-head addition is also somewhat more abundant in the case of halogenated monomers such as vinyl chloride. The preponderance of head-to-tail additions is understood to arise from a combination of resonance and steric effects. In many cases the ionic or free-radical reaction center occurs at the substituted carbon due to the possibility of resonance stabilization or electron delocalization through the substituent group. Head-to-tail attachment is also sterically favored, since the substituent groups on successive repeat units are separated by a methylene... 

Monsanto s SEE modacryhc is the only remaining U.S. produced modacryhc flame-tesistant fiber. This fiber is a combination of halogen monomers and a dye receptor to offset the poor dye penetration characteristic of acrylonitrile-vinyl halogen copolymers. 

The introduction of halogenated monomers into the backbone results in highly increased vulcanization properties. 

Jaeger RJ, Conolly RB, Reynolds ES, et al. 1975. Biochemical toxicology of unsaturated halogenated monomers. Environmental Health Perspectives 11 121-128. 

A list of some anionically polymerizable unsaturated monomers is given in Table 5. They can be listed in four classes styrenic monomers, hydrocarbons monomers, halogenated monomers, and polar monomers. As a general principle, a good match between the nucleophilicity of the initiator and the electron affinity of the double bond is essential to obtain good initiation efficiency without side reactions. 

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. 

The future outlook for CFCs is bleak. With decreasing demand and production over the last ten years and an almost total phase-out planned, their future is limited, though not nonexistent. Because of their use for producing halogenated monomers, they will continue to play an important but smaller role in the chemical industry. 

Rempp and Franta [3] described the synthesis of macromonomers either by using redox catalysis with halogenated monomers (vinyl chloride, vinyl dichloride, or even trifluorochloroethylene) or by using a radical initiation with (meth)acrylates. In the latter case, thiol compounds were used as transfer agents (Scheme 46) [251] ... 

The telomerization process is certainly an appropriate technique for the synthesis of (meth)acrylic-type macromonomers, but also of (meth)acrylo-nitrile-derived macromonomers. This technique is open to almost all conventional monomers but is also devoted to original monomers such as NIPAM. We can note that macromonomers based on halogenated monomers were synthesized by telomerization, using redox catalysis. 

Some Mo, Os and other organometallic species show not only SFRP but also ATRP activity. This will depend on the nature of halogen, monomer and ligands. Thus, there are many systems that show a concurrent involvement of spontaneous activation/deactivation (SFRP), a catalyzed process (ATRP) and a degenerative exchange (DT) and their contributions to the overall control depend on the stmcture of reagents but also reactions conditions (concentration, temperature, light, additives, etc.)... 

Other methods that have been reported include inducing the cyclization reaction by incorporating thioamide groups [491], copolymerized AF-vinylpyrrolidone [492], or vinyl halogen monomers in copolymerized or grafted form [493]. Stabilizers based on maleic acid are also effective [494,495]. Reviews on the subject have been published by Brown [496] and Krcma [497]. 

Dyed in wet spinning during wash stage or pigmented dope Blend of moisture absorbing and finedenier staple fibers Incorporate halogen monomers, such as vinylidene chloride and antimony compounds Cationic dye sites quaternary ammonium compounds... 

The use of halogenated monomers or reactive intermediates can bring about a lowering of heat of combustion. For example, heat capacity and heat of combustion have been determined for copolymers of styrene with polyesters whose thermodynamic properties were known introduction of chlorine into the polyester molecule lowered the heat of combustion. The temperatures of self-ignition of polyesters containing 17.5% and 23.7% chlorine were 580 and 650 °C, respectively. 

Melting of Copolymers Study of the melting of random copolymers is justified for such practically important copolymers as polyacrylonitrile (PAN), polyacetals, propylene copolymers, ethylene copolymers, and ethylene vinyl acetate copolymers. The majority of PAN polymers are copolymers of acrylonitrile with halogenated monomers (with the purpose of imparting... 

Scheme 14 Typical examples of polymerization of halogenated monomers with iodo-compounds.

The second class of halogenated monomers studied in DT with alkyl iodides deals with chlorinated monomers and especially VC (CH2=CHC1) and vinylidene chloride (CH2=CCl2). 

T able 1 The magnitude (in a.u.) and size (in A ) of the o-holes of halogenated monomers and the energies of the lowest unoccupied molecular orbital (LUMO)... 

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