Poly styrene-b-

As previously described, all microspheres discussed in this chapter were synthesized from AB type diblock copolymers. Precursor block copolymers, poly(styrene-b-4-vinyl pyridine) (P[S-b-4VP]) diblock copolymers, were synthesized using the additional anionic polymerization technique [13]. The basic properties of the block copolymers were determined elsewhere [24,25] and are listed... 

The poly(styrene-b-isoprene) (P(S-b-IP)) and poly(-styrene-b-2-vinyl pyridine) (P(S-b-2VP)) block copolymers with narrow molecular weight distributions for blending with the microspheres were also synthesized using the additional anionic polymerization technique. The number-average molecular weights (Mns) and PS contents are also shown in Table 1. 

Cao X. and Faust R., Polyisobutylene based thermoplastic elastomer 5. Poly(styrene-b-isobutylene-b-styrene) tri-block copolymers by coupling of living poly(styrene-b-isobutylene) di-block copolymers. Macromolecules, 32, 5487, 1999. 

Jacob S., Majoros I., and Kennedy J.P., Novel thermoplastic elastomers Star-blocks consisting of eight poly(styrene-b-isobutylene) arms radiating from a calex[8]arenecore. Rubber Chem. TechnoL, 71, 708, 1998. 

The physical properties of the acid- and ion-containing polymers are quite interesting. The storage moduli vs. temperature behavior (Figure 8) was determined by dynamic mechanical thermal analysis (DMTA) for the PS-PIBMA diblock precursor, the polystyrene diblock ionomer and the poly(styrene)-b-poly(isobutyl methacrylate-co-methacrylic acid) diblock. The last two samples were obtained by the KC>2 hydrolysis approach. It is important to note that these three curves are offset for clarity, i.e. the modulus of the precursor is not necessarily higher than the ionomer. In particular, one should note the same Tg of the polystyrene block before and after ionomer formation, and the extension of the rubbery plateau past 200°C. In contrast, flow occurred in... 

Figure 8. DMTA behavior for poly(styrene)-b-poly(isobutyl methacrylate-co-methacrylic acid) potassium salt.

Brown and White employed this approach to prepare block copolymers of styrene and mcthacrylic acid (6). They were able to hydrolyze poly(styrene-b-methyl methacrylate) (S-b-MM) with p-toluenesulfonic acid (TsOH). Allen, et al., have recently reported acidic hydrolysis of poly(styrene-b-t-butyl methacrylate) (S-b-tBM) (7-10). These same workers have also prepared potassium methacrylate blocks directly by treating blocks of alkyl methacrylates with potassium superoxide (7-10). 

Preparation of Block Copolymers. Poly(styrene-b-methyl methacrylate) and poly(styrene-b-t-butyl methacrylate) were prepared by procedures similar to those reported for poly(styrene-b-methyl methacrylate (12,13). Poly(methyl methacrylate-b-t-butyl methacrylate) was synthesized by adaptation of the method published (14) for syndiotactic poly(methyl methacrylate) polymerization of methyl methacrylate was initiated with fluorenyllithium, and prior to termination, t-butyl methacrylate was added to give the block copolymer. Pertinent analytical data are as follows. 

At this point a comparison of these observations with those reported by Allen, et al. (7-10), for the reaction of poly(styrene-b-isobutyl methacrylate) with potassium superoxide should be made. 

Neutralization with KOH in aqueous THF gave the desired poly(styrene-b-potassium methacrylate) (S-b-MA.K). The carbonyl band in the IR spectrum is replaced with a strong, broad carboxylate absorption centered near 1566 cm 1 (Figure 2c). The carboxylate and potassium contents were assayed by non-aqueous titration and ICP, respectively. The resulting values of 0.91 meq COj /g and 0.98 meq K/g indicate essentially quantitative conversion to the potassium methacrylate. S-b-MA.K obtained in this manner is easily dissolved in solvents such as THF and dichloromethane, in contrast to the... 

In summary, we have examined several new methods for cleaving ester groups in poly(styrene-b-alkyl methacrylates). Short blocks of methyl methacrylate are very difficult to hydrolyze, but can be cleaved with reagents such as lithium iodide and potassium trimethylsilanolate. These latter reagents, however, result in side-reactions which appear to crosslink the polymer. 

SEBS Poly(styrene-b-ethylene butylene-b-styrene)... 

First of all, these materials are ttractive "per se". In particular, poly(styrene-b-caprolac tone) is a semi-crystalline product displaying an amazing resistance to cold-fracture, and also macroscopically biodegradable at least when PCL represents the continuous phase. It can be "organized" into single crystals, wherein lamellae of PSt and PCL alternate with a periodicity of about 80 A. 

It was demonstrated that poly(styrene-b/oc -vinylpyrrolidone) beads (0 220 nm) are suitable for preparation of pH nanosensors [12]. Various fluorescein derivatives were embedded and did not leach out of the beads due to functionalization with highly lipophilic octadecyl anchor. The pK., of the indicators inside the nanobeads varied from 5.8 to 7.7 making them suitable for various biotechnological, biological and marine applications. The beads based on a lipophilic l-hydroxypyrene-3,6, 8-trisulfonate (pKa 6.9) were also manufactured. 

Since Lewis base additives and basic solvents such as tetrahydrofuran are known to deaggregate polymeric organolithium compounds, (21,23,26) it was postulated that ketone formation would be minimized in the presence of sufficient tetrahydrofuran to effect dissociation of the aggregates. In complete accord with these predictions, it was found that the carbonation of poly(styryl)lithium (eq. 9), poly(isoprenyl)-lithium, and poly(styrene-b-isoprenyl)lithium in a 75/25 mixture (by volume) of benzene and tetrahydrofuran occurs quantitatively to produce the carboxylic acid chain ends (8 ). 

Elabd, Y. A., Napadensky, E., Walker, C. W. and Winey, K. 1. 2006. Transport properties of sulfonated poly(styrene-b-isobutylene-b-sytrene) triblock copolymers at high ion-exchange capacities. Macromolecules 39 399-407. 

Since their commercial introduction by Shell in 1965, the poly(styrene-b-(buta-diene or isoprene)-b-styrene) triblock copolymers (SBS or SIS) have attracted a... 

Preparation of Octa-Arm Poly(styrene-b-isobutylene) Stars... 

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