Living polystyrene, preparation

Preparation of Macromolecular Dioxolenium Salts. Living polystyrene prepared by the polymerization of styrene in THF with a-methylstyrene tetramer dianion reacted with a 2.1-molar amount of ethylene oxide for three hours at room temperature a 6.6-molar amount of adipoyl chloride was added, and the mixture was stirred for 20 horns a 20-molar amount of ethylenebromohydrin was added. This mixture was stirred for 44 hours. The bromoethylated polystyrene was precipitated in excess methanol and freeze-dried from benzene in a vacuum system. A 1-nitropropane solution of polystyrene dioxolenium salt was prepared by reaction of bromoethylated polystyrene with silver perchlorate in 1-nitropropane. Silver bromide was removed from the reaction mixture by filtration. Molecular weight of the product was measured by a vapor-pressure osmometer it was 1910 for living polystyrene and 5190 for the bromoethylated polystyrene. Bromine analysis of the bromoethylated polystyrene showed 67.9% of the calculated value. 

Block copolymers containing polysiloxane segments are of great interest as polymeric surfactants and elastomers. Polycondensation and polyaddition reactions of functionally ended prepolymers are usually employed to prepare well-defined block copolymers. The living polystyrene anion reacts with a,co-dichloropoly(dimethyl-siloxane) to form multiblock copolymers398. ... 

Nobutoki, K., and Sumitomo, H., Preparation of block copolymer of e-caprolactone with living polystyrene. Bull. Chem. 

Polystyrene was prepared by the anionic polymerisation of styrene in toluene plus THF mixtures (4 1 volume ratio) using n-butyl lithium as initiator. After removing a sample for analysis at this stage, the remainder of the living polystyrene was reacted with a five molar excess of trichloromethylsilane for 15 min and then excess methanol introduced. The methoxy-terminated polystyrene was freeze-dried from dioxan. The method described here essentially follows the route proposed by Laible and Hamann (6). 

The polydispersity of polymers prepared in this way is usually very low for example, a value MJM of 1.05 was found for a sample of poly(a-methylsty-rene). Living polymers can also be used for the preparation of block copolymers after the consumption of the first monomer, a second anionically polymerizable monomer is added which then grows onto both ends of the initially formed block. By termination of the living polymer with electrophilic compounds the polymer chains can be provided with specific end groups for example, living polystyrene reacts with carbon dioxide to give polystyrene with carboxylic end groups. 

Preparation of the Living" Polystyrene. 18 g of the living polymer was prepared by standard anionic polymerization using n-butyl lithium. The reaction was carried out by the dropwise addition of 20 ml of styrene to 5 ml of the initiator solution in 150 ml of neat THF at -78°C. The styrene drip was adjusted to take approximately 30 min for completion and then the reaction was allowed to stir for two hours before the grafting reaction with mesylated lignin was carried out. The number average molecular weight of the polystyrene, as determined by HPSEC, was 9500 with polydispersity of 1.2. 

Preparation of desired molecular weight polystyryl carbanion ( Living Polystyrene ) by anionic polymerization (Fig. 2). Anionic polymerization has been used extensively to provide control over molecular weight with narrow molecular weight distribution. 

Reaction of the mesylated lignin prepared in step 1 (Fig. 1) with the polystyryl carbanion (living polystyrene) from step 2 (Fig. 2). The carbanion displaces the mesylate groups on the lignin in a nucleophilic displacement reaction with the formation of the polystyrene-lignin graft copolymer (Fig. 3). 

Preparation of the strontium salt of one-ended living polystyrene (SrS )... 

On the other hand, Ishizu et al. [58] reported the synthesis of cyclic polystyrene using interfacial condensation reaction of a/o-dibromopolyslyrcnc prepared from living polystyrene initiated with sodium naphthalene and terminated with 1,4-dibromobutane and then tetramethylenediamine as depicted in Fig. 11. The reaction was carried out in organic solvent/water to yield in more than 90%. The effect of solvent on the yield of cycUc polymer was observed, and the yield of cyclic product obtained in DMSO was higher than that in toluene. Since DMSO dissolves in both water and toluene, the reaction proceeded faster than that in toluene. 

At the beginning, MACROMER was basically polystyrene prepared by anionic polymerization and subsequent reaction of the living end to produce a polymerizable group selected from the groups shown in Table 3 42). 

The living ends of a suitable polymer may initiate polymerization of another monomer, and thus lead to the synthesis of block polymers free of homopolymers. For sample, one prepares living polystyrene then adds pure methyl methacrylate to its solution and produces in this way a block polymer of styrene and methyl methacrylate (22). Actually, it is possible to produce living polymers with two active ends which can form a block polymer containing three segments—ABA. 

The reactive end of a living polymer attacks a suitable group on a dead polymer Pji and grafts on Pjj as shown by Schreiber (15), who grafted living polystyrene on dead poly (methyl methacrylate). Such a procedure may lead to cross linking or to the formation of a loop, if both ends of the living polymer are active. Other block polymers prepared by this technique are polymers of styrene and ethylene oxide (14), polymers of styrene and dimethylsiloxanes (13), and polymers of styrene and vinylpyridine (16). 

An alternative approach to synthesizing block copolymers with Ionic linking groups was later developed. Polystyrene with tertiary amine and groups was prepared by the reaction of living polystyrene with a, w-chloroamlnes such as 3-(dlmethylamlno)propyl chloride (20) (Equation (16). This reaction was shown to take place with at least... 

This is an example of the preparation of ABA-type thermoplastic elastomer. Styrene is polymerized first since styryl initiation of isoprene is faster than the reverse reaction. The reaction is carried out in a nonpolar solvent with Li" " as the counterion to enable predominantly cis-l,4-polyisoprene to be formed in the second growth stage. The living polystyrene-6/ocfc-polyisoprene AB di-block copolymer resulting from the second stage is then coupled by a double nucleophilic displacement of Cl ions from a stoichiometric equivalent of dichloromethane to give a polystyrene-61ock-polyisoprene-/)/ock-polystyrene triblock copolymer. 

Blocks. The synthesis of block copolymers were attempted in the following manner. "Living" polystyrene was first prepared by conventional anionic techniques using n-BuLi as the initiator in THF at -78 C. In initial experiments, this polystyryl lithium product was treated with AICI3 to afford a polystyryl A1 species which could be capable of alkylating Ti(0Bu)4. However, we find it to... 

The most widely used method for the preparation of PS macromonomers is the one developed by Milkovich [46]. Living polystyrene solutions were reacted with ethylene oxide to form the less reactive alkoxide and then with methacry-loyl chloride (MAC), according to the following reaction (Scheme 31). 

Kinetic and conductance investigations of the sodium and cesium salts of living polystyrene in dimethoxyethane, DME, were first reported by Shimomura, Smid, and Szwarc282. The kinetic data had to be extrapolated to 0 time due to the instability of the sodium salt in that solvent. For the same reason a direct conductance study was prevented. The cesium salt, prepared by initiating the polymerization with cumyl cesium, is more stable in DME than the sodium salt therefore, the pertinent kinetic observations and conductance studies were readily accomplished. 

Anionic polymerization frequently has been used to prepare well-defined living polymers such as polystyrene, poly(a-methylstyrene), polydienes, which may be transformed by two methods into block copolymers with cationically polymerizable monomers. When a living anionic polymer is mixed with a stoichiometric amount of a living cationic polymer the cationic and anionic species may couple. For example, anionic living polystyrene (St) or poly (a-methylstyrene) (MSt) were reacted with living cationic polytetrahydrofuran (THF). In the latter system the coupling efficiency was low, probably because of proton or hydride transfer 132) ... 

The living polymers generated by anionic polymerization are well suited to the preparation of block polymers. Adding 1,3-butadiene to a living polystyrene block sets the stage for attaching a poly( 1,3-butadiene) block. 

As mentioned earlier, fiee radical polymerization using 2,2,6,6-tetiamethyl-1 -piperidinylo (TEMPO) (21b) would allow living polystyrene to be made with reduced chain transfer reactions. If successful, such controlled fiee radical polymerization can be important processes that will compete well with traditional anionically prepared copolymers. 

Preparation of styrene-diene block copolymers involves sequential addition of the diene monomer to "living" polystyrenes. The resulting polymer is an AB block copolymer consisting of segments of styrene mers and diene mers. 

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