Polystyrene triblock copolymer

Antony, P., Puskas, J.E., and Kontopoulou, M. The Rheological and Mechanical Properties of Blends Based on Polystyrene-Polyisobutylene-Polystyrene Triblock Copolymer and Polystyrene. Proceedings of MODEST, International Symposium on Polymer Modification, Degradation and Stabilization, Budapest, Hungary, 2002. 

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. 

A polystyrene-poly(ethylene,l-butene)-polystyrene triblock copolymer is produced by the selective hydrogenation of the corresponding triblock copolymer in which the center block consists of random placements of 1,2-poly(1,3-butadiene) and 1,4-poly (1,3-butadiene) units. 

Li ZB, Chen ZY et al (2005) Disk morphology and disk-to-cylinder tunability of poly(acrylic acid)-b-poly(methyl acrylate)-b-polystyrene triblock copolymer solution-state assemblies. Langmuir 21 7533-7539... 

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.)...

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. 

Block Copolymer Synthesis by Three-Step Sequential Monomer Addition The preparation of block copolymers by sequential addition of monomers using living anionic polymerization and a monofunctional initiator is the most direct method for preparing well-defined block copolymers. Detailed laboratory procedures for anionic synthesis of block copolymers are available [37, 230], Several important aspects of these syntheses can be illustrated by considering the preparation of an important class of block copolymers (Scheme 7.22), the polystyrene-fe-polydiene-( -polystyrene triblock copolymers. 

Certain block copolymers, for example polyfethylene oxide)-polystyrene triblock copolymers, can form micelles in the suspoision medium and this may hinder the production of laige particles, since nucleatitm may occur within the micelle. However, the use of shorter diblocks of the same compositicm oiables micron-sized particles to be prepared [32]. 

NMP of styrene in a miniemulsion can be also performed in a tubular reactor [213]. In the first step, a macroinitiator is prepared by bulk polymerization in a batch reactor and the subsequent miniemulsion polymerizatiOTi is carried out in a tubular reactor. The polymerization kinetics in the tubular reactor are similar to those in a batch reactor. It is also noteworthy that both preparatimi of a macroinitiator and a miniemulsion polymerization can be achieved in a crmtinuous tubular reactor to obtain polystyrene-h/ock-poly(butyl acrylate) diblock and polystyrene-h/ocA -poly (butyl acrylate)-h/ocA -polystyrene triblock copolymers [214],... 

Hempenius, M.A., et al. 1998. A polystyrene-oHgothiophene-polystyrene triblock copolymer. JAm Chem Soc 120 2798. 

Li, K. and Q. Wang. 2004. Synthesis and solution aggregation of polystyrene-oligo(p-phenyle-neethynylene)-polystyrene triblock copolymer. Macromolecules 37 1172. 

Polystyrene-b-polyisoprene-b-polystyrene triblock copolymers of different composition were also prepared in a similar... 

Scheme 102 One-pot synthesis of polyfluorene-polystyrene triblock copolymers...

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 effect of molecular weight of atactic polystyrene-i -poly(ethylene-co-butylene)-b-atactic polystyrene triblock copolymers on the morphology, impact strength, and... 

NA, not applicable SEES, polystyrene-(polyethylene/polybutylene)-polystyrene triblock copolymer. 

An alternative approach is to incorporate reactive functional groups Into the elastomer, producing an in-situ graft copolymer. This reduces interfacial tension, improving dispersion in processing, and improves the adhesion of the rubber to the thermoplastic In the solid state. A maleated polystyrene/poly(ethylene-co-butylene)/polystyrene triblock copolymer (SEES) has been used successfully to toughen polyamides and polyesters. 

Block copolymers are long-chain molecules composed of multiple blocks of distinct monomers (see Fig. 17). They are widely used as adhesives, and because they can reduce interfacial energy they can act as compatibilizers in polymer blends. In addition, many of the novel and fascinating properties of block copolymers arise from microphase separation. Thermoplastic elastomers, such as polyurethanes and polystyrene-polyisoprene-polystyrene triblock copolymers, act like cross-linked elastomers, although there is no true cross-linking. Instead, rubbery portions of the... 

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.)... 

Another unique approach toward low 6 is to disperse fine foams in PI films, since the e of air is unity. This technique developed by Hedrick et al. [208] typically involves the preparation of PS-PAA-PS (PS polystyrene) triblock copolymer, imidization, and finally higher temperature annealing where thermally labile PS block undergoes thermolysis (depolymerization) to form submicron pores. They utilized a variety of other thermally unstable block such as poly(a-methylstyrene), poly(propylene oxide), PMMA, poly(e-caprolactone), and aliphatic polyesters and examined the effects of chemical structure, fraction, and molecular weight of the block on the resultant morphology (pore size, shape, porosity) and dielectric and thermal, and mechanical properties. In this case, the resulting porous structure depends on the initial microphase separation domain structure of the thermally labile triblock. For example, nano-foamed PI (19% porosity) prepared from triblock consisting of PMDA-3F [3F = l,l-bis(4-amino-phenyl)-l-phenyl-2,2,2-trifluoroethane] (see Fig. 62 for its structure) and poly(propylene oxide) showed a considerably lower e = 2.3) than that of the non-porous homo PMDA-3F e = 2.9) [209]. 

T. Yamaguchi and E. Yamada, Preparation and mechanical properties of clay/polystyrene-block-polybutadiene-block-polystyrene triblock copolymer (SBS) intercalated nanocomposites using organoclay containing stearic acid. Polymer International, 55 (2006), 662-7. 

Poly sty rene-b-polybutadiene-b-polystyrene triblock copolymer ... 

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