Styrene-butadiene star polymer

As a first comprehensive 2D experiment, Kilz et al. [36] described the characterization of complex styrene-butadiene star polymers. The four-arm star polymers were prepared by anionic polymerization to give samples with perfect composition and molecular weight control. The polymerization was designed to yield a mixture of linear (of molar mass M), two-arm (2M), three-arm (3M), and four-arm (4M) species. Four samples with varying butadiene content (about 20,40, 60, and 80%) were prepared. The 2D verification sample was a mixture of four samples with different chemical composition and molar masses. Therefore, this verification sample consisted of 16 components representing the wide range in chemical composition and molar mass. 

Figure 17.8a is the TEM image of a styrene/butadiene star block copolymer containing 74% (by volume) styrene. The nanostmctured morphology arises from the fact that the constituents - that is, polystyrene (PS) and polybutadiene (PB) chains -are connected chemically by covalent bonds which do not permit a macroscopic segregation of the polymer chains. Due to the presence of a unique molecular architecture of the copolymer, the star block copolymer was found to show a cocontinuous arrangement of the nanostmctures [69-72]. The star block copolymer specimen was treated -with osmium tetroxide vapor prior to TEM imaging such treatment... 

Block copolymer chemistry and architecture is well described in polymer textbooks and monographs [40]. The block copolymers of PSA interest consist of anionically polymerized styrene-isoprene or styrene-butadiene diblocks usually terminating with a second styrene block to form an SIS or SBS triblock, or terminating at a central nucleus to form a radial or star polymer (SI) . Representative structures are shown in Fig. 5. For most PSA formulations the softer SIS is preferred over SBS. In many respects, SIS may be treated as a thermoplastic, thermoprocessible natural rubber with a somewhat higher modulus due to filler effect of the polystyrene fraction. Two longer reviews [41,42] of styrenic block copolymer PSAs have been published. 

Figure 9-19. A universal gel-permeation chromatography calibration curve obtained from measurements on linear poly(styrene) (O), comb-branched poly(styrene) (O ), star-branched poly(styrene) ( ), poly(methyl methacrylate) ( ), poly(vinyl chloride) (a) c -l,4-poly-(butadiene) (A), poly(styrene)-poly(methyl methacrylate) block copolymer (Qj ), random copolymer from styrene and methyl methacrylate O), and ladder polymers of poly(phenyl siloxanes) ( ) (according to Z. Grubisic, P. Rempp, and H. Benoit).

Tween 81. See Polysorbate 81 Tween 85 Tween 85LM. See Polysorbate 85 Twinkling Star. See Antimony trioxide Two-stage phenolic resin. See Novolac resin Two-stage resin. See Phenolic resin Ty-lon B11. See Sodium sulfite Tylac 037 Tylac 97-422 Tylac 692 Tylac 757 Tylac 820 Tylac 936 Tylac 979-RG Tylac 68009-00 Tylac 68010-00 Tylac 68012-00 Tylac 68013-00 Tylac 68014-00. See Styrene/butadiene polymer Tylac 68060-00. See Acrylonitrile copolymer Tylac 68073-00 Tylac 68074-00 Tylac 68075-00 Tylac 68076-00. See Butadiene-acrylonitrile elastomer, carboxyl-terminated Tylac 68150-00 Tylac 68151-00. See Butadiene/acrylonitrile copolymer Tylac 68152-00. See Styrene/butadiene polymer... 

In addition, block copolymers can be produced by adding a second monomer once the first one has completely reacted. Tri- and multi-block copolymers can be prepared by subsequent additions of different monomers. Thus, styrene-butadiene-styrene tri-block copolymers produced by anionic polymerization are used as thermoplastic elastomers. Also, star and hyperbranched polymers can be obtained through this technique by simply using suitable initiation systems [17]. 

Styrene-butadiene block copolymers (SBC) with a high (70-85 %) styrene content are commercially produced and marketed as transparent, stiff, and tough thermoplastic resins under the trade names of Styrolux (Styrolution), K-Resin (Chevron-Phillips), Finaclear (Total petrochemical), and Clearene (Denka-Kaguku). Unlike other more elastomeric types of styrene-butadiene block copolymers, the rigid SBC resins contain only <25 % polybutadiene rubber content. Structurally, these SBC polymers are composed of polystyrene (S) and polybutadiene (B) blocks, linked together in an unsymmetrical star-block [(S-B)x] structure. 

Serrano, E., Zubeldia, A. et al. Effect of different thermal treatments on the self-assembled nanostructures of a styrene-butadiene-styrene star block copolymer. Polymer Degradation and Stability, 83 (2004), p. 495-507... 

Since all p-star polymers still possess several DPE functions, the synthetic sequence may possibly further continue to synthesize higher armed and compositional star-branched polymers. It should be mentioned that styrene derivatives were generally used herein both for facile synthesis of highly reactive living anionic polymers and for easy characterization of the resulting stars by H NMR, but living anionic polymers of 1,3-butadiene, isoprene, and certain functional styrene and 1,3-dienes can also be employed in the iterative methodology. 

Michler GH, Adhikari R, Lebek W, Goerlitz S, Weidisch R, Knoll K. Morphology and micromechanieal deformation behavior of styrene/butadiene-bloek eopolymers. 1. Toughening mechanisms in asymmetric star block copolymers. J Appl Polym Sci 2002 85(4) 683-700. 

With the exception of a few commercial polymers such as polyisobutylene, polybutadiene and styrene-butadiene block copolymers, living polymers are prepared in small quantities under stringent conditions. Larger amounts can only be prepared by repeating the synthesis many times, and this is a costly and time-consuming process. In the case of hydrogenated polybutadiene, to prepare samples that resemble polyethylene, the need for a secondary reaction step renders the preparation even more costly. This has so far limited the extent to which it has been possible to use these materials to test models. Cell et al. [ 18] prepared asymmetric stars with structures similar to ethylene-propylene copolymers by hydrogenation of star-branched polyisoprene. The reactions to produce these materials took up to three weeks, and... 

The linear polymers, as shown above, can be built up by the sequential addition of monomer or by coupling the living anionic chains using compounds like dichloro dimethylsilane. Hence, the base polymer would have styrene polymerized first, followed by butadiene, and then addition of the coupling agent. If a multifunctional coupling agent such as silicon tetrachloride is used, a radial block or star-branched SBS is formed. 

Despite the drawbacks of this method, it has been used to prepare a tremendous number of polypeptide hybrid block copolymers (Table 1), and when carefully executed provides reasonably well-defined samples. Synthetic polymer domains have been prepared by addition polymerization of conventional vinyl monomers, such as styrene and butadiene, as well as by ringopening polymerization in the cases of ethylene oxide and e-caprolactone. The generality of this approach allows NCA polymerization off of virtually any primary amine functionality, which was exploited in the preparation of star block copolymers by polymerization of sarcosine NCA from an amine-terminated trimethyleneimine dendritic core [37]. In most examples, the polypeptide domain was based on derivatives of either lysine or glutamate, since these form a-helical polypeptides with good solubility characteristics. These residues are also desirable since, when deprotected, they give polypep-... 

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