Polystyrene halogenation

For (b), a block copolymer, in which one side of the block has affinity to the solvent and the other block to the polymer particle, is the most reasonable stabilizer. Block copolymers of polystyrene/halogenated polybutadiene, polystyrene/ polyethyleneglycol, and polystyrene/PDMS are examples of this type of stabilizer (12). When using a block copolymer, it is possible to provide appropriate amphiphilic and other surface properties by changing the block ratio. For example, when using a block copolymer of polystyrene/PDMS for polymerization of methyl methacrylate in hexane, the ratio of polystyrene/polydimehtylsiloxane should be below 4.4 (13). If the ratio is above 4.4, the block copolymer forms a stable micelle and will not function properly as a stabilizer. 

Polymers with saturated carbon chain backbone include polyolefins, polystyrenes, halogenated polyolefins, halogenated polystyrenes, polyvinyls substituted with various groups such as -OH, -OR, -0(0)C-R, -C(0)0-R, -C(0)-R, -C5H4N, etc. In this class also are included polyacrylates, polymethacrylates, polymers with ketone groups in the backbone, as well as other polymers with saturated carbon chain backbone. The polymers with a saturated carbon chain backbone form the most important and common class of polymers. 

Table 17. Inorganic Synergists—Halogen System for Polystyrene and ABS...

In polymers such as polystyrene that do not readily undergo charring, phosphoms-based flame retardants tend to be less effective, and such polymers are often flame retarded by antimony—halogen combinations (see Styrene). However, even in such noncharring polymers, phosphoms additives exhibit some activity that suggests at least one other mode of action. Phosphoms compounds may produce a barrier layer of polyphosphoric acid on the burning polymer (4,5). Phosphoms-based flame retardants are more effective in styrenic polymers blended with a char-forming polymer such as polyphenylene oxide or polycarbonate. 

Flame Retardants. Flame retardants are added to nylon to eliminate burning drips and to obtain short self-extinguishing times. Halogenated organics, together with catalysts such as antimony trioxide, are commonly used to give free-radical suppression in the vapor phase, thus inhibiting the combustion process. Some common additives are decabromodiphenyl oxide, brominated polystyrene, and chlorinated... 

DMPPO—polystyrene blends, because of the inherent flame resistance of the DMPPO component (oxygen index ca 29.5), can be made flame retardant without the use of halogenated additives that tend to lower impact strength and melt stabiUty in other polymers. Approximately one-half of total Noryl sales volume is in flame-retarded grades, ie, VO or VI in a 1.6-mm section (UL-94). 

Deposition Precursors. Diamond has been deposited from a large variety of precursors which include, besides methane, aliphatic and aromatic hydrocarbons, alcohols, ketones, and solid polymers such as polyethylene, polypropylene, and polystyrene, and halogens. 

The combination of radiation-sensitive and radiation-resistant groups is interesting. Halogen substitution of the phenyl group in polystyrene results in high radiation sensitivity with inter-molecular crosslinking. 

Berlin and coworkers (5,56) desired to obtain a material with an increased mechanical strength. They carried out a plasticization of bulk ami emulsion polystyrene molecular weight 80000 and 200000 respectively at 150-160° C, with polyisobutylene, butyl rubber, polychloroprene, polybutadiene, styrene rubber (SKS-30) and nitrile rubber (SKN 18 and SKN 40). The best results were obtained with the blends polystyrene-styrene rubber and polystyrene-nitrile rubber. An increase of rubber content above 20-25% was not useful, as the strength properties were lowered. An increase in the content of the polar comonomer, acrylonitrile, prevents the reaction with polystyrene and decreases the probability of macroradical combination. This feature lowers the strength, see Fig. 14. It was also observed that certain dyes acts as macroradical acceptors, due to the mobile atoms of hydrogen of halogens in the dye, AX ... 

These results indicate that if polydienes and similar polymers can be prepared quantitatively with tertiary amine terminal groups, then they can be combined with other halogen functional polymers using established techniques to create interesting new block copolymer systems. For example, consider the reaction between telechelic pyridine terminated polybutadiene and monofunctional bromine terminated polystyrene (equation 4) -the latter has been prepared in 95% yield. >it The product would be an ABA... 

Ni(PPh3)4] Halogenated cross-linked polystyrene Ethylene 58... 

We note from Table VIII a strong interest in halogenated resists, particularly those substituted with chlorine. The addition of chlorine to the aromatic structure of polystyrene has a marked effect on cross-linking efficiency. Monodisperse polystyrene, for example, has a sensitivity on the order of 50 p C/cm2, yet with as little as 20% chloromethyl groups substituted on the ring, the sensitivity is improved to 2 C/cm2 for comparable molecular weight and distribution. 

Miscellaneous ligands so far incorporated into the polystyrene matrix include imidazolyl [21], 2-amido oxime [22], thioether and sulfoxide moieties [23]. The procedure is simple and essentially involves the halogen-replacement of Cl- or Br- from polystyrene matrix, bearing CH2C1, or Br- groups. Mostly, first row transition element salts undergo facile complexation with these modified polystyrene matrices [21] (Fig. 11). 

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