Monomers halogenated styrenes

G. Kaszas, Halogenated terpolymers of isobutylene, diolefin monomer and styrenic monomer, US Patent 6960632, assigned to Bayer Inc. (Sarnia, CA), November 1, 2005. 

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. 

As reactive flame-retardants, halogenated styrenes such as monochlorostyrene or dibromostyrene may be admixed with the monomer mixture. 

Relative reactivities in the copolymerization of pora-halogenated styrene monomers with styrene in the presence of trifluoromethanesulphonic acid were influenced strongly by the addition of excess counterions and by solvents of low polarity. Undissociated centres were thought to be more selective in monomer addition than the dissociated species, since similar alterations in relative reactivities were not observed in the corresponding metal halide-initiated systems. An influence of solvent polarity on relative reactivities in these systems has been noted by other workers,and multiparameter correlations based on monomer structure, solvent, temperature, and initiator type have been developed. ... 

ATRP is also a method to obtain bloekeopolymers from different monomers with styrene [168,169]. If the first bloek is terminated with a halogen end group, it works as a macroinitiator in the presence of transition metal eatalysts under a reversible redox mechanism, following the same seheme as in homopolymerization. The formation of tri- and multibloekstructures is also praetieable. 

Many other vinyl aromatic monomers and polymers were synthesized and investigated during this postwar period of discovery following styrene s early commercial success. Polymers of vinyl toluene, based on a more plentiful supply of toluene, had properties similar to those of polystyrene and were proposed as an attractive alternative (5). During this time, there was also great Interest in o-methylstyrene (6), divlnylbenzene (7) and various halogenated styrene monomers (8). 

Radio-chemical graft copolymerization with good efficiency on halogenated polyolefins has been carried out by contacting the substrate with monomer (styrene) vapor [158,159]. Interpenetrating polymer network (IPN) could be made by grafting the monomers on preirradiated substrates... 

Iodine is unique among the halogens in that it initiates polymerization of the more reactive monomers (styrene, vinyl ether, acenaphthylene. /V-vinylcarbazole) even in the absence... 

Monomers devoid of polar groups generally undergo anionic polymerization in a predictable manner. With polar monomers sometimes side reactions occur during the process transfer reactions in the case of acrylonitrile, or propylene oxide, and even more so with alkylacrylates deactivations (or "killing") reactions in the case of halogen substituted styrene or dienes. 

Epoxy vinyl ester resins are a special class of unsaturated resin. This resin is made by capping an epoxy resin with methacrylic acid and then dissolving in styrene monomer to the desired viscosity. This gives mechanical properties similar to epoxy resins, but the processibility (low viscosity allowing for resin infusion processes) of an unsaturated polyester resin. As with unsaturated vinyl esters, the most common fire retardant vinyl ester resin is based on a resin made from a halogenated system, tetrabromobisphenol A. The level of bromine in the resin and the presence of antimony will determine the fire performance of the resin. These resins are normally used for corrosion resistant equipment or when fire performance and high mechanical properties are required. It is very difficult to get a low smoke value with a brominated vinyl ester resin again due to the fact that bromine... 

Materials may exhibit a tainting odor from the polymers, monomers, additives, adhesives, or process. Packaging related taints, as reported from the Nestle s Central Packaging Laboratory over a 4-year period (1996-2000) were related to solvents (28%), degraded polyethylene (PE) (24%), styrene (15%), halogenated phenols (15%), degraded paper (3%),... 

Henrici-Olive and Olive were the first to put forward the hypothesis that complexes are sometimes formed between the active centre and the monomer and or/solvent [45], As only the complex with monomer is capable of propagation, part of the centres is inhibited and the polymerization rate is reduced. This theory was found to be valid with styrene [46], but not with MMA [47]. Burnett called attention to the important circumstance that radicals solvated in various ways may react differently, or at least at different rates [47]. His conclusions were based on kinetic studies of MMA polymerization in various halogenated aromatics. In the copolymerization of butyl vinyl ether with methacrylates, complex formation between the active centre and condensed aromatics prior to monomer addition was observed by Shaik-hudinov et al. [48], The growing polymer forms a stable donor-acceptor complex with naphthalene, described by the formula. 

The presence of a carbon-halogen bond is not absolutely essential for the occurrence of tranfer to monomer. Moore et al. [37] studied styrene polymerization with y-irradiation. They measured thermodynamic quantities, particularly the Gibbs energy, enthalpy, entropy and volume changes by the method of rotating sectors and found that transfer to monomer is negli-... 

These different mechanisms and prodnct distribntions, to some extent, are related to the bond dissociation energies, the chain defects of the polymers, and the degree of aromaticity, as well as the presence of halogen and other heteroatoms in the polymer chains. Large amount of styrene monomers can be obtained by pyrolysis of PS, while a wide range of hydrocarbons are prodnced by random degradation of PE and PP [3, 59, 60]. 

Figure 9-1 illustrates inductive influences in cationic polymerizations. The electron-releasing inductive influence of alkyl groups causes isobutene to polymerize very quickly at low temperatures where propylene reacts inefficiently and ethylene is practically inert. For similar reasons, a-methylstyrene (9-12) is more reactive than styrene, and substitution of an electron-withdrawing halogen for an ortho- or/ ara-hydrogen, decreases the monomer reactivity still further. As a corollary, ortho- and para-electron-releasing substituents (RO—, RS—, aryl) increase cation stability and monomer reactivity. 

We can summarise the situation with styrene by a few observations. Obviously this monomer is not easily attacked by the trityl ion and the most favourable case encountered is that in which trityl hexafluoroantimonate it used. Termination reactions seem to plague most of these polymerisations and we believe that halogen-ion transfer from the anion to the growing species soon after initiation is responsible for the loss of activity of these systems. Again, the SbF counterion is an exception in that it does not seem to undergo this termination reaction. Except for the last study discussed, little reliable evidence is available to date to elucidate these difficult problems. Much fundamental information could be obtained by continuing on the line followed by Johnson and Pearce. 

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