Polystyrene triblock copolymers with

Figure 13.13 Reduced storage modulus G and dynamic viscosity rj = G /w as functions of reduced frequency uto) for a cylinder-forming polystyrene-polybutadiene-polystyrene triblock copolymer with block molecular weights of 7000-43,000-7000. The curves are time-temperature-shifted to a reference temperature of 138°C the open symbols were obtained in the low-temperature ordered state the closed symbols were obtained in the high-temperature disordered state. (From Gouinlock and Porter 1977, reprinted with permission from the Society of Plastics Engineers.)...

E.) Bromination of Polyisobutylene and Polystyrene triblock copolymer with ditolylethylene. 

Triblock copolymers, as shown in Fig. 5.8 d), comprise a central homopolymer block of one type, the ends of which are attached to homopolymer chains of another type. As with other block copolymers, the components of triblocks may be compatible or incompatible, which will strongly influence their properties. Of particular interest are triblocks with incompatible sequences, the middle block of which is rubbery, and the end blocks of which are glassy and form the minor phase. When such polymers phase-segregate, it is possible for the end blocks of a single molecule to be incorporated into separate domains. Thus, a number of rubbery mid-block chains connect the glassy phases to one another. These materials display rubber-like properties, with the glassy domains acting as physical crosslinks. Examples of such materials are polystyrene/isoprene/polystyrene and polystyrene/polybutadiene/polystyrene triblock copolymers. 

The group of Abetz [77] used polystyrene-fcZocA -poly(l,2-butadiene)-block-polyitert-hutyl methacrylate) triblock copolymers with partially hydrolyzed poly(tert-butyl methacrylate) blocks, together with polystyrene-... 

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. 

This was utilized by Tian et al. [168] to prepare a new class of liquid crystal homopolymers of poly ll-[4-(3-ethoxycarbonyl-coumarin-7-oxy)-carbonyl-phenyloxy]-undecyl methacrylate] containing a coumarin moiety as a photocross-linkable unit. The preparations included polymers of various chain lengths. Also, hquid crystaUine-coil diblock and hquid crystalline-coil-liquid crystalline triblock copolymers with polystyrene as the coil segment were formed. The polymers were reported to have been synthesized with the aid of atom transfer radical polymerization. The dimerization of the coumarin moieties takes place upon irradiation with light of A > 300 nm to yield cross-linked network structures. 

Zhou Q, Brumer H, Teeri TT (2009) Self-organization of cellulose nanocrystals adsorbed with xyloglucan oligosaccharide-poly(ethylene glycol)-polystyrene triblock copolymer. Macromolecules 42 5430-5432... 

The characteristic ratio, C, is much smaller (1.08) for the ABA chains in the large micelles than in the small aggregates formed at weak segregation [34], since most of the chains form loops. Loops appear to be dominant in the micelle formed in A,Ai-dimethyl acetamide by a large triblock copolymer with polystyrene as the soluble internal block and poly(tert-butylstyrene) as the insoluble terminal blocks [26]. 

Three SBS triblock copolymers with different compositions and block lengths (Table 1) were obtained from Shell Development Co, they are designated here as 0.48 PS, 0.29 PS, and 0,27 PS to reflect their polystyrene (PS) content. It should be noted that two of these have comparable PS... 

A useful, hydrocarbon-soluble, dilithium initiator has been prepared by the dimerization of 1,1-diphenylethylene with lithium in cyclohexane in the presence of anisole (15 vol%) as shown in equations 14 and 15 (43). Although the initiator was soluble in this mixture, it precipitated from solution when added to the polymerization solvent (cyclohexane or benzene). Therefore, the dilithium initiator was chain extended with approximately 30 units of isoprene to generate the corresponding soluble oligomer. This initiator was used to prepare well-defined polystyrene-6ZocA-polyisoprene-6/oc -polystyrene and poly(a -methylstyrene)-6Zoc -polyisoprene-6ZocA-poly(o -methylstyrene) triblock copolymers with >90% 1,4-microstructure by sequential monomer addition. 

Siegfried and co-workers (66,67) investigated thermoplastic IPNs based on SEES triblock copolymers with a polystyrene ionomer. Two subclasses of thermoplastic IPNs were identified those prepared by a sequential polymerization method, and those prepared by mechanically blending separately synthesized polymers. In each case, a polystyrene acid sulfate was neutralized dynamically in the melt with a concentrated solution of sodium hydroxide. The water steamed off rapidly under the reaction conditions. The first subclass resulted in lower melt viscosities, but more nearly equal dual-phase continuity was achieved with the second subclass. The subject of thermoplastic IPNs was recently reviewed by Sperling (68). 

Suppose that a polystyrene-h/ocA -polybutadiene-h/oc -polystyrene triblock copolymer is synthesized with block molecular weights of 10,000-80,000-... 

Figure 40 (a) Phase SFM image of a polystyrene-block-oligothiophene-block-polystyrene triblock copolymer cast on mica from a solution in toluene (1 mg/ml). (b) Micelles built by the same triblock system as observed in a closed film by phase SFM (after Fourier filtering). (Reprinted from M.A. Hempenius, B.M.W. Langeveld-Voss, J.A.E.H. van Haare, R.A.J. Janssen, S.S. Sheiko, J.P. Spatz, M. Moeller, and E.W. Meijer. J. Am. Chem. Soc. 120 2798, 1998. Copyright [1998] American Chemical Society. With permission.)... 

It is interesting to note that some of their electron micrographs exhibit features similar to those of a linear polystyrene-block-poly((4-vinylbenzyl)di-methylamine)-block-polyisoprene triblock copolymer with almost equal amounts of the three components, when cast from benzene [168] (Fig. 16c,d). Also a quaternary star copolymer consisting of polystyrene, polyisoprene, polybutadiene, and poly(4-methylstyrene) was reported, but no morphological characterization was given [79]. 

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