Bromine with polystyrene

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... 

Almost all electrophilic substitutions known to proceed in solution with isopropylbenzene can also be performed with polystyrene, using solvents such as nitrobenzene, carbon disulfide, or carbon tetrachloride. These substitutions include bromination [42], nitration [43,44], sulfonylation, Friedel-Crafts acylations [45 49], and alkylations... 

Cross-linked polystyrene can be acylated with aliphatic and aromatic acyl halides in the presence of A1C13 (Friedel-Crafts acylation, Table 12.1). This reaction has mainly been used for the functionalization of polystyrene-based supports, and only rarely for the modification of support-bound substrates. Electron-rich arenes (Entry 3, Table 12.1) or heteroarenes, such as indoles (Entry 5, Table 15.7), undergo smooth Friedel-Crafts acylation without severe deterioration of the support. Suitable solvents for Friedel-Crafts acylations of cross-linked polystyrene are tetrachloroethene [1], DCE [2], CS2 [3,4], nitrobenzene [5,6], and CC14 [7]. As in the bromination of polystyrene, Friedel-Crafts acylations at high temperatures (e.g. DCE, 83 °C, 15 min [2]) can lead to partial dealkylation of phenyl groups and yield a soluble polymer. 

Saigusa, T., and R. Oda Bromination of polystyrene with N-bromosuccini-mide, debromination of the brominated polystyrene, and grafting of vinyl acetate on the backbone of debrominated polystyrene. Bull. Ind. Chem. Research, Kyoto Univ. 33, 126 (1955) Chem. Abstr. 50, 1357 (1956). 

Though we have shown only one bromine atom and hence only one Ph2P group on the polymer, almost all of the benzene rings in polystyrene can be functionalized if the bromopolymer is made by bromination of polystyrene in the presence of a Lewis acid. Now the phosphine can be alkylated with an alkyl halide of your choice to form a phosphonium salt, still on the polymer. 

The order of effectiveness of halogens is I > Br > Cl > F [20]. Iodine-containing organic compounds are too thermally unstable to be melt compounded with polystyrene, and organoflorine comounds are too thermally stable to be effective as flame retardants. This leaves bromine- and chlorine-containing compounds as the most effective flame retardants. 

Polymer-supported Wittig reagents were first prepared more than 20 years ago [32]. It has been shown that the success of the reaction depends strongly upon (i) the preparation of the reagent by bromination and phosphination of cross-linked polystyrene rather than by co-polymerization using styryldi-phenyl phosphine, and (ii) the generation of the phosphorane with a base/ solvent system that swells the phosphonium sites in the polymer network (Scheme 6) [33]. Thus, bromination of polystyrene 1 yielded phenyl bromide 32, and this was followed by phosphination with n-butyUithium and chlor-odiphenylphosphine or with Hthium diphenylphosphide to give 33, a compound which is commercially available (Scheme 6). 

The literature reports the synthesis of two types of catalyst based on tungsten and molybdenum chemically bonded with the polymer, and their use in the metathesis of oleflns with internal C=C bonds [264]. The catalysts are synthesized by bromination of polystyrene containing 2% divinylbenzene with subsequent treatment of the brominated polymer by n-BuLi in tetrahydrofuran. Lithium-polystyrene derivatives are thus formed. After reaction with a,a -dipyridyl or Ph2PCl, they are converted, respectively, to dipyridyl (A) or phosphine (B) derivatives of polystyrene that form active complexes after being heated with W(CO)5 or Mo(CO). ... 

Hence, the insensitivity to addition sequence for styrene and (AA) monomers makes it relatively easy to form (PS-fc-PAA), (PS-fc-PAA-fc-PS), and (PAA-Z -PS-Z -PAA) di- and tiiblock copolymers. However, when AN and MMA are involved, the poly(acrylonittile) block must be formed first, i.e., second monomer addition should be in the order shown in the preceding text. Unlike NMP methods, the use of ATRP presents no major problems when preparing block copolymers containing acrylates and methacrylates. Triblock (ABC) copolymers can be prepared by starting with a bromine-terminated polystyrene macroinitiator to polymerize Z-butyl acrylate, followed by methyl acrylate or methyl methacrylate using a CuBr/pentamethyl diethylene triamine catalyst. 

Bromination of polystyrene with iV-bromosuccinimide and benzoyl peroxide in CCI4 at room temperature can achieve a 61% conversion in four hours. Considerable degradation, however, accompanies this reaction. 

As additive flame-retardants, low-molecular halogenated aliphatics are used, like hexachloroethane (CI3C—CCI3) or chlorinated paraffins. Brominated aliphatics, such as tetrabromoethane (Br CH - CHBrg) are preferably suggested for foams because of their lower processing temperature. Alicyclic compounds such as hexabromo-cyclododecane are readily compatible with polystyrene and efficient in relatively low proportions. 

Improvements beyond the empirical, direct additivity of heat capacities is needed at low temperatures, where skeletal vibrations govern the heat capacities. With only few measured points it is possible to establish the functional relationship of the 0, and 3 temperatures with concentration for the inter- and intramolecular vibrations (see Sect. 2.3). The group-vibration frequencies are strictiy additive, so that heat capacities of complete copolymer systems can be calculated using the ATHAS, as discussed in Sect. 2.3.7. hi Fig. 2.70 the glass transition changes with concentration, to reach 373 K for the pure polystyrene, as for the previously discussed copolymer systems with polystyrene. Below T, the solid Cp of both components needs to be added for the heat capacity of the copolymer, above, the liquid Cp must be used. The glass transition retains the same shape and width as seen in Fig. 7.68 on the example of brominated poly(oxy-2,6-dimethyl-l,4-phenylene) [29]. 

Sodium peroxide is another useful reagent for the fusion of polymer samples preparatory to analysis for metals such as zinc and non-metals such as chlorine [15,16] and bromine. In this method the polymer is intimately mixed either with sodium peroxide in an open crucible or with a mixture of sodium peroxide and sucrose in a micro-Parr bomb. After acidification with nitric acid, chlorine can be determined [16]. In a method for the determination of traces of bromine in polystyrene in amounts down to 100 ppm bromine, a known weight of polymer is mixed intimately with pure sodium peroxide and sucrose in a micro-Parr bomb which is then ignited. The sodium bromate produced is converted to sodium bromide by the addition of hydrazine as the sulfate ... 

High impact polystyrene can pass the UL-94 V-O rating by adding 12% aromatic bromine with 4% KR Grade Sb203. 

Suitable salts were those of perchloric acid or, preferably, of hexafluorophosphoric acid." " Experiments carried out with bromine-terminated polystyrene or polybutadiene gave a rapid precipitation of silver bromide even at low temperatures, due to the resonance stabilization of the benzylic or the allylic carbenium ions thus generated. The efficiency of block copolymer formation was found to be determined by factors such as the structure of the carbenium ion, the nature of the gegenion, the experimental conditions and, of course, the nature of the second monomer. Under carefully chosen conditions, THF could be polymerized to form living cationic block copolymers... 

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... 

Amos prepared his polymer-supported reagent in two steps from commercially available polystyrene beads (bromination, then condensation with lithium diphenylphosphide). He found that a useful range of sulphoxides could be reduced effectively, in good yields and in a few hours, to give clean samples of sulphides. 

Silane radical atom transfer (SRAA) was demonstrated as an efficient, metal-free method to generate polystyrene of controllable molecular weight and low polydispersity index values. (TMSlsSi radicals were generated in situ by reaction of (TMSlsSiH with thermally generated f-BuO radicals as depicted in Scheme 14. (TMSlsSi radicals in the presence of polystyrene bromide (PS -Br), effectively abstract the bromine from the chain terminus and generate macroradicals that undergo coupling reactions (Reaction 70). 

For the large scale synthesis, the sodium salt of 2 formed in the NaCN-NaOH reaction could be purified by brominated polystyrene resin S P-207 chromatography to avoid acidic work-up which generates HCN. The SP-207 resin was first saturated with 1 M NaCl, and the crude reaction mixture was loaded onto the column. The column was then eluted with 1M NaCl to remove inorganic salts such as excess NaCN and NaOH and other polar impurities. Eluant switching to MeOH-H20 eluted the sodium salt of 2. Fractions containing >98.5 A% of... 

The synthesis of luminescent organoboron quinolate polymers (21) (Fig. 15) via a three-step procedure starting from a silylated polystyrene has been communicated. The synthesis was initiated by the highly selective borylation of poly (4-trimethylsilylstyrene) (PS-Si), followed by the replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with substituted thienyl groups (R = H, 3-hexyl, 5-hexyl). In the final step, the 8-hydroxyquinolato moiety was introduced. The hexyl-substituted polymers efficiently emitted light at 513-514nm upon excitation at 395 nm.40... 

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