Polystyrene-polybutadiene diblock

Figure 14. Gel permeation chromatograms of polystyrene and polystyrene-polybutadiene diblock copolymer prepared with Ba-Mg-Al. Conditions solvent, cyclohexane 50° C.

Sehwier CE, Argon AS, Cohen RE. Crazing in polystyrene-polybutadiene diblock copolymers containing cylindrical polybutadiene domains. Polymer 1985 26(13) 1985—1993. 

The experimental studies on phase behavior and pattern formation reviewed here have been done on substrate-supported films of cylinder-forming polystyrene- foc -polybutadiene diblock (SB) [36, 43, 51, 111-114] and triblock (SBS) [49, 62, 115-117] copolymers (Table 1), lamella-forming polystyrene- /ocfc-poly(2-vinyl pyridine) diblock copolymers (SV) [118, 119] and ABC block terpolymers of various compositions [53, 63, 120-131], In simulation studies, a spring and bid model of ABA Gaussian chains has been used (see Sect. 2) [36,42, 58, 59],... 

The substantial work on polystyrene/polybutadiene and polystyrene/ polyisoprene blends and diblock and triblock copolymer systems has lead to a general understanding of the nature of phase separation in regular block copolymer systems (5,6). The additional complexities of multiblocks with variable block length as well as possible hard- and/or soft-phase crystallinity makes the morphological characterization of polyurethane systems a challenge. 

The coordination of metals to various other pendant sites present in block co-polymers has also been explored. For example, metal coordination to the olefinic groups present in the polybutadiene (PB) blocks of polystyrene-/ -polybutadiene (PS-/ -PB) diblock and PS- -PB-3-PS triblock copolymers has been reported.This was achieved by the reaction of PS-/ -PB with various metal complexes such as Fe3(CO)i2, [Rh(/r-Cl)(CO)2]2, PdCl2(NCMe)2, and PtCl2(NCMe)2 to afford materials with Fe-, Rh-, Pd-, and Pt-containing blocks. Intermolecular cross-linking was possible but solubility in organic solvents was maintained and micellization was observed in most cases. However, on solvent removal and drying, many of the polymers became insoluble. 

Starting in the 1980 s, a number of governmental recycling policies created a demand for recycled thermoplastic olefin (TPO) for post-consumer applications. Since polystyrenes and TPOs are not miscible, polystyrene-TPO diblock copolymers are being developed to reduce the interfacial tension in PS/TPO blends. TPOs are tough materials with low stififiiess properties. If blended with polystyrene, they improve the toughness of polystyrenes. If compatibilized, the properties of PS/TPO should be similar to styrene-hydrogenated polybutadiene rubbers. 

As an example of blends with attractive interactions, Fig. 65 shows a superstructure in which interactions between methacrylic acid groups and pyridine side groups of a polystyrene-fc-polybutadiene-fo-poly(f-butyl methacry-late-staf-methacrylic acid) (PS-b-PB-b-P(MAA-sfaf-fBMA)) triblock quater-polymer and a PS- -P2VP diblock copolymer lead to a wavy lamellar structure with cylinders from mixed P2VP and P(MAA-sfaf-fBMA) blocks [194],... 

The use of these initiators to polymerize LA814 and methylglycolide815 has been reported to proceed in a well-controlled fashion. Block copolymers such as PCL-b-PLA have also been prepared. Elimination of PrOH from the reaction of (270) with preformed hydroxyl terminated polymers, followed by lactone polymerization, yields diblocks of CL with polystyrene or polybutadiene.816 The preparation of an ABA triblock has also been reported (A = CL, B = LA) since propagating chains of PLA do not initiate CL ring opening, (270) was pretreated with hydroxy terminated (PCL-b-PLA)-OH 814... 

The most simple diblock copolymers are linear chains, in which one part of the chain consists of one type of monomer, say polystyrene (PS), and the other one of another type, say polybutadiene (PB), as illustrated in Figure 14. PS and PB usually phase separate at low temperatures however, because of their chemical connectivity, block copolymers cannot unmix on a macroscopic scale. They can only phase separate on a microscopic scale, the size of which is determined by the length of the polymers. 

In solution, block copolymers display interesting colloidal and interfacial properties. They can be used as emulsifying agents in water-oil and oil-oil systems (6 ). In the later case, the oil phases are solid and they give rise to polymeric alloys (7.) or they are liquid and they allow the preparation of latexes in organic medium (8 ). However, the molecular structure of block copolymers based on polybutadiene PB (70 ) and polystyrene PS behave as thermoplastic elastomers when engaged in multiblock (PB-PS)n or triblock (PS-PB-PS) structures but never when implied in inverse triblock or diblock arrangements. Similarly the... 

A gel permeation chromatogram obtained by Heller (13) indicated that Kraton 101 contained 1% polystyrene, 22% polystyrene/1,4-poly-butadiene, and 77% polystyrene/1,4-polybutadiene/polystyrene, apparently because the material is manufactured by coupling of the diblock. The diblock would be present if the coupling reaction is not 100% efficient. Kraton 101 would thus be essentially a blend of ABBA and AB block copolymers. Assuming that Kraton 102 is manufactured in the same way, the molecular weight of the ABBA block copolymer results as about 72,000 from the above data, the polystyrene blocks having a molecular weight of about 12,000, and the polybutadiene center block one of about 48,000. 

The morphologies of polystyrene-F-polybutadiene (PS-F-PBD) diblock copolymers confined in a nanopore were observed by Shin and Xiang (Shin et al., 2004), in which a lot of attentions were paid to the layer number of the concentric cylinder barrel structure as a function of the nanopore radius. In this work, the symmetrical and asymmetrical... 

The comparison of BS and symmetric BSB copolymers derived from the BS polymer by addition of a B block identical to the first one has demonstrated that the addition of a third block to a diblock copolymer achieves a stretching of both the polybutadiene and the polystyrene chains92. ... 

Polystyrene and ABS are the polymers that are most commonly modified with SBCs. SBS triblocks and SB diblocks with 30-40% styrene are often used in concentrations near 5% either as a toughener alone in combination with polybutadiene in high-impact polystyrene. In addition to the use of elastomeric... 

A variation of the HIPS process uses diblock polybutadiene-polystyrene rubbers to produce core-shell rubber particles with polystyrene cores and thin polybutadiene shells. The small particle size of 0.1 to 0.4 pm is less than optimum for toughening but provides a high-gloss material. 

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