Polystyrene-polybutadiene

Interpenetrating networks of DMPPO and polymers such as polystyrene, polybutadiene, poly(urethane acrylate), and poly(methyl methacrylate) have been prepared by cross-linking solutions of DMPPO containing bromomethyl groups with ethylenediamine in the presence of the other polymer (68). 

Thermoplastic Elastomers. These represent a whole class of synthetic elastomers, developed siace the 1960s, that ate permanently and reversibly thermoplastic, but behave as cross-linked networks at ambient temperature. One of the first was the triblock copolymer of the polystyrene—polybutadiene—polystyrene type (SheU s Kraton) prepared by anionic polymerization with organoHthium initiator. The stmcture and morphology is shown schematically in Figure 3. The incompatibiHty of the polystyrene and polybutadiene blocks leads to a dispersion of the spherical polystyrene domains (ca 20—30 nm) in the mbbery matrix of polybutadiene. Since each polybutadiene chain is anchored at both ends to a polystyrene domain, a network results. However, at elevated temperatures where the polystyrene softens, the elastomer can be molded like any thermoplastic, yet behaves much like a vulcanized mbber on cooling (see Elastomers, synthetic-thermoplastic elastomers). 

SBS (linear or star) Polystyrene Polybutadiene Polystyrene Polyethylene Thermoplastic elastomer... 

Addition of poly(styrene-block-butadiene) block copolymer to the polystyrene-polybutadiene-styrene ternary system first showed a characteristic decrease in interfacial tension followed by a leveling off. The leveling off is indicative of saturation of the interface by the solubilizing agent. 

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. 

Anionic polymerization of polystyrene takes place very rapidly- much faster than free radical polymerization. When practiced on a large scale, this gives rise to heat transfer problems and limits its commercial practice to special cases, such as block copolymerization by living reactions. We employ anionic polymerization to make tri-block copolymer rubbers such as polystyrene-polybutadiene-polystyrene. This type of synthetic rubber is widely used in the handles of power tools, the soft grips of pens, and the elastic side panels of disposable diapers. 

Consider a polystyrene-( )-polybutadiene star block copolymer with four arms coupled by a central Si-atom. Or consider a metal catalyst (e.g., Au) supported in activated carbon. Then the scattering of only the selected element (Si, Au, respectively) can be extracted [242], Even the distribution of the elements in the material can be mapped based on ASAXS data. A concise review of the ASAXS method in combination with AXRD and AWAXS has been published by Goerigk et al. [243]. 

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

Table 10.1. Polystyrene- -Polybutadiene Block Copolymers Used as Starting Materials 1...

Styrolux is an example of a nanostructured polymer which is used in food packaging. It is a polystyrene-polybutadiene block copolymer where polymer chains are build up of alternating polystyrene and polybutadiene blocks. These blocks appear as dark lamellae in the TEM image due to the staining of the polybutadiene with OSO4. This structured nanoscale architecture of the pol5mier, which can be controlled during manufacture, allows the optimum combination of impact resistance and transparency. 

A block copolymer containing 75 mass % of polybutadiene and 25 mass % of polystyrene polybutadiene-Z)/ocA -polystyrene (0.75 0.25 w)... 

The properties of such heterogeneous polystyrene/polybutadiene blends mainly depend on the following parameters ... 

Preparation of a Polystyrene/Polybutadiene-Blend (High Impact Polystyrene, HIPS) by Polymerization of Styrene in the Presence of Polybutadiene... 

The high-pressure phase behavior of polymer-solvent-supercritical carbon dioxide systems was investigated experimentally The polymers used were poly(methyl methacrylate), polystyrene, polybutadiene, and poly(vinyl ethyl ether) at concentrations ranging from 5 to 10% in mixtures with toluene or tetrahydrofuran. The experiments were conducted for temperatures from 25 to 70°C and pressures up to 2200 psi in a high-pressure cell (Kiamos and Donohue, 1994). 

Calibration curves were developed for HPSEC-DV using polymer standards including narrow MWD polystyrenes, polybutadienes, polymethyl-... 

Polystyrene-polybutadiene-polystyrene block-copolymers were also heparinized via formation of acetal bonds. The procedure involved oxidation of the copolymer to glycol 90) ... 

The above thermal analysis studies demonstrated the enhanced thermal stability of POSS materials, and suggested that there is potential to improve the flammability properties of polymers when compounded with these macromers. In a typical example of their application as flame retardants, a U.S. patent39 described the use of preceramic materials, namely, polycarbosilanes (PCS), polysilanes (PS), polysilsesquioxane (PSS) resins, and POSS (structures are shown in Figure 8.6) to improve the flammability properties of thermoplastic polymers such as, polypropylene and thermoplastic elastomers such as Kraton (polystyrene-polybutadiene-polystyrene, SBS) and Pebax (polyether block-polyamide copolymer). 

Fig. 7. Example of electron micrograph of the centered cubic structure. Copolymer polystyrene-polybutadiene SB. 71 containing 13% polybutadiene, swollen with 25% styrene, and post-polymerized. Black circles are polybutadiene spheres...

Douy has synthetized polystyrene-polybutadiene (SB) block copolymers of various molecular weights and compositions66 by anionic polymerization, under high vacuum, in tetrahydrofuran dilute solution (less than 5%), at low temperature (—70 °C), and with cumyl potassium as initiator. Resulting from the polymerization conditions, the microstructure of the polybutadiene block is 90% 1,2 and 10% 1,4. 

Fig, 8. Example of phase diagram concen-tration/temperature. Copolymer polystyrene-polybutadiene SB. 31 containing 20% poly butadiene and exhibiting a Hexagonal structure. 

The study by low-angle X-ray diffraction and electron microscopy of concentrated solutions of the copolymers in preferential solvents for polybutadiene (iso-prene, butadiene) or for poly(a-methyl styrene) (styrene, a-methylstyrene, methyl methacrylate, methylethyl ketone) and of copolymers in the dry state obtained by slow evaporation of the solvent from the mesophases have shown the existence of three types of structure hexagonal, lamellar, and inverse hexagonal depending upon the copolymer composition84,85. The factors governing the structural type and the structural parameters are the same as in the case of polystyrene-polybutadiene copolymers85. ... 

Block copolymers of butadiene and vinyl-2-naphtalene (BVN) have been synthetized and studied by the same techniques as polybutadiene-poly(a-methyl styrene) and polystyrene-polybutadiene block copolymers86,87. They exhibit the same structures, namely lamellar and cylindrical as SB and BMS block copolymers86,87. ... 

We shall examine the range of stability of the ordered structures of copolymers containing an amorphous polystyrene, polybutadiene or poly(ethyl methacrylate) block and acrystallizable polyethylene oxide) (PEO) or poly(e-caprolactone) (PCL) crystallizable block and the factors that determine the existence and the geometrical parameters of such periodic structures. 

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. 

Phase Relationships. The first systematic investigation of the two-phase behavior of polymer/polymer/solvent systems was probably made by Dobry and Boyer-Kawenoki (2) for a variety of polymer pairs, and more recently this work was extended by Kern and Slocombe (3) and Paxton (35) to a number of other systems including several vinyl polymers. Typically, the three-component phase behavior is as shown in Figure 19 for the polystyrene/polybutadiene/benzene system (2), where a one-phase (polystyrene/polybutadiene/benzene) region is separated by a phase boundary from a two-phase (polystyrene-rich/benzene and polybutadiene-rich/benzene) mixture. As with any three-component system of this type, a critical point exists somewhere near the maximum of the phase boundary, and appropriate tie lines give the compositions and amounts of the respective phases in the two-phase region. 

Figure 19. Ternary phase diagram for the polystyrene/ polybutadiene/benzene system. (After Dobry and Boyer-Kawenoki (2).)...

One further example might be the thermoplastic elastomer, triblock copolymer of polystyrene, polybutadiene, and polystyrene, in that order. The polybutadiene in this case has been grafted with poly (methyl methacrylate). The proposed nomenclature is shown in Equation 17. For emphasis, the notation is read from top to bottom, and from left to right. 

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