PS/PBD/styrene

Gailard and coworkers [215, 266] demonstrated the surface activity of block copolymers by studying the interfacial tension reduction in demixed polymer solutions. Addition of a FS-b-FBD diblock copolymer to the PS/PBD/styrene ternary system showed first a characteristic decrease in interfacial tension followed by a leveling off, which is similar to the evolution of interfacial tensions for oil-water systems in the presence of surfactants. The early investigations were more of case studies that demonstrated the phenomenon without giving the fundamental detail required to help the understanding of the emulsification process and the factors that govern it. 

HIPS and ABS are heterogeneous materials containing dispersed rubber particles in continuous vitreous matrixes. Figure 4.4(a) and (b) exhibit the typical salami morphologies of HIPS and ABS when produced in bulk processes with PBD rubber. These products are nontransparent, due to their relatively large particle sizes. Figure 4.5 compares the stress-strain curves of PS, poly(styrene-co-acrylonitrile) (SAN), HIPS and ABS. The area under... 

ABA triblock copolymers, where A was PBd and B either PS or PMMA were prepared by the combination of ROMP and ATRP techniques [122], The PBd middle blocks were obtained through the ROMP of cyclooctadi-ene in the presence of l,4-chloro-2-butene or cis-2-butene-l,4-diol bis(2-bromo)propionate using a Ru complex as the catalyst. The end allyl chloride or 2-bromopropionyl ester groups were subsequently used for the ATRP of either styrene or MMA using CuX/bpy (X = Cl or Br) as the catalytic system (Scheme 50). Quantitative yields but rather broad molecular weight distributions (Mw/Mn higher than 1.4) were obtained. 

Recent investigations in our laboratory involve the controlled radical polymerization of styrene, initiated by dicumyl peroxide 8 in the presence of Tempo [71,72]. Molecular weights are obtained in the range 2500-300000 with narrow polydispersity (Mw/Mn = 1.5). From such capped Tempo polystyrene 9, polysty-rene-6-chloromethylstyrene (PS-6-PCMSty) [171], PS-h-PBd and PS-h-PBd- -PS block copolymers are prepared with Mw = 50000 and Mw/Mn = 1.5 [72] ... 

Metalation of PI and PBd by this procedure and subsequent polymerization of styrene led to the formation of PI- -PS and PBd-g-PS copolymers with well-defined molecular characteristics144-148 (Scheme 66). 

Ma et al.177 synthesized a,co-dilithium poly(styrene-b-butadiene-b-styrene)s (PS-b-PBd-b-PS) by using l,3-bis(l-phenylethylenyl)benzene activated with 2 mol of s-BuLi as initiator for the sequential polymerization of butadiene and styrene in the presence of s-BuOLi in benzene. The cyclization reaction was performed under high dilution in cyclohexane with either dichlorodimethylsilane or MDPPE (Scheme 87). The cyclic copolymer was isolated by fractional precipitation. The only indication of the formation of this architecture was the lower intrinsic viscosity. 

A substantial amount of work has been done on the ozone degradation of polymers. For Instance, mechanical properties and adhesion have been shown to degrade sharply during ozone exposure (1-4). Polystyrene (PS) and polybutadiene (PBD) show very different sensitivities to ozone exposure. Since reaction with a gas would occur first at the surface, we planned to study the reactivity of the PBD as affected by copolymerization with styrene. In particular it was of Interest to know if random and block copolymers of styrene would show different surface sensitivities because of changes in surface distribution of the groups. For the same group concentration, block structures should segregate PS better. 

Two different types of (PS-b-PBDh) diblock can be presently synthesized. The first one by classical anionic initiation (s-buty1-lithium) and "living" propagation of the (PS-b-PBD) copolymer (8), followed by the hydrogenation procedure described here as discussed above, the resulting product will be close to a (PS-b-LLDPE) copolymer. The second one came from the discovery (9) of a "living" polymerization of butadiene into a pure (99 %) 1,4 polymer by a bis n allylnickel-tri-fluoroacetate) coordination catalyst, followed by styrene polymerization unfortunately, the length of the polystyrene block is limited (to a M.W. of ca. 20,000) by transfer reactions. 

The monomers, N-vinyl carbazole (NVC), methacrylamide (MAM), octadecyl methacrylate (ODMA) and trichloroethyl methacrylate (TCEM) were obtained from Polyscience, Inc. Diphenyl acetylene (DPAE), poly(4-chlorostyrene) (PC1S), poly(butadiene) (PBD), poly(styrene) (PS) were obtained from Aldrich Chemical Co. Poly (vinyl alcohol) (PVA), 99-100% hydrolyzed, was obtained from J. T. Baker Chemical Co. Poly(vinyl pyrrolidone) was obtained from Sigma Chemical Co. 

Non-0-SoIutions. A number of data have been published for the intrinsic complex modulus of flexible polymers in good solvents. Tanaka, Sakanishi and coworkers studied the system of PIB in cyclohexane (2,92,98), polymethyl methacrylate (PMMA) in chloroform (2,9/), PMS in benzene and in toluene (94,99) and a few copolymers of styrene-butadiene in toluene and in cyclohexane (100). Schrag, Ferry et al. reported the results on PS in a-chloronaphthalene and in a chlorinated diphenyl (3), polybutadiene (PBD) in a-chloronaphthalene and in Decalin (101) and PMS in Decalin and in a-chloronaphthalene (102). In all these cases, the frequency dependence of the intrinsic complex modulus is qualitatively described as more Rouse-like as compared with the results for -solutions. Apart from the physical appropriateness, any of the three versions of the Zimm theory can be applied to the experimental results the original Zimm integrodifferential equation... 

ABS-type resins are used as impact modifiers for PVC, but the resultant blend has insufficient transparency for application in clear bottles. Transparency can be obtained by grafting PMMA onto crosslinked PBD (5) or poly (butyl acrylate) (6) which has been previously grafted onto PS (Diagram 4). In this case the PMMA branch is compatible with PVC by virtue of its solubility parameter, and optical clarity results from suitable component ratios in the graft copolymer so that the refractive index matches that of PVC. The desired results are not obtained if a copolymer of methyl methacrylate and styrene is... 

The polystyrene/styrene/polybutadiene (PS/S/PBD) system occurs in the production of high impact polystyrene. The process for making toughened polystyrene as described by Moulau and Keskkula (1) starts with a rubber in styrene solution. As S is polymerized to PS, phase separation results in immediate formation of droplets of a PS phase. With further polymerization, the PS phase increases in volume until phase volumes are equal. At this point, phase inversion occurs—the dispersed PS phase becomes the continuous phase and the PBD phase becomes the disperse droplets. Complete conversion of S to PS yields the commercially important high impact polystyrene. 

Samples of linear PBD (Mw = 149,000 Mw/Mn = 1.46) and PS (Mw = 290,000 Mw/Mn = 3.0) were dissolved at six levels of total solids in S in jars on a roll mill. Styrene polymerization was prevented by adding 0.1% benzo-quinone. The two-phase mixtures were separated by centrifugation 15 min at 20,000 rpm in a Beckman model 21 ultracentrifuge, and the solutions were then frozen in the metal centrifuge tubes. Frozen plugs were removed as needed by warming the outside of the tube. They were then sectioned at the interface, warmed to 25°C, and the solids level in each phase was measured by methanol... 

In 1965 Shell Oil Co. introduced styrenic TPEs, under the trade name Kraton, which are polystyrene-b-polyisoprene(or polybutadiene)- -polystyrene (PS-b-PI(or PBd)- -PS linear triblock copolymers, made by anionic polymerization. Later, BASF introduced styrenic PTEs having tapered blocks (i.e., Styroflex). The typical styrene content of TPEs is between 25 and 40wt.%. When more stable TPEs, toward oxygen. 

Table 4.2 Heterogeneous polymerization of styrene in the presence of PBD for the production of HIPS. Reaction kinetics applied onto both phases (the PS- and the PB-rich phase) [30] (s = 0,1,2,...) [b, n,m = 1,2,3,...)...

A thermal treatment has been used by Sasakawa et al. to modify the surfaces of polyoxymethylene (POM) and acrylonitrile-butadiene-styrene (ABS) resins [162]. The results showed that the heat treatment eliminates oxygen from POM to form hydrocarbons at the surface while it oxidizes the surface of PBD and PS. 

For several years, polymers were expected to be miscible only when there was favorable specific interaction between them. Gibbs free energy of mixing was developed and shown to contain three different contributions combinatorial entropy of mixing, exchange interaction, and a free volume term. Specific interactions are a prerequisite for the miscibility of polymers. This was the drift that the Nobel laureate P. Flory indicated as discussed in Chapter 1. A number of exceptions to this rule have been found. A number of miscible systems have been found to have a random copolymer as one of the blend constituents. Both the copolymers that were found miscible with random microstructure are butadiene-styrene copolymer and vinyl chloride and vinyl acetate copolymers. The homopolymers PBd, PS, PVC, and PVA can form six binary blends. This is from C2 = 6. They are not miscible in any of the six binary blends that can be formed from four homopolymers. This would mean that there are no specific interactions... 

Onion structure In styrene-butadiene block copolymer blends with polystyrene, the copolymer forms spherical particles consisting of numerous concentric shells, with PS and PBD alternating 3.32, 3.33... 

Fig. 4. Glass transition temperatures Tf) in S-B-S and SBR. PBD = Polybutadiene PS = Polystyrene SBR = Styrene-butadiene rubber.

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