Solution micelles polystyrene

WI1 Winoto, W., Tan, S.P., Shen, Y., Radosz, M., Hong, K., and Mays, J.W., High-pressure micellar solutions of polystyrene-Z>/ocA -polybutadiene and polystyrene-Z)/ >c -polyisoprene in propane exhibit cloud-pressure reduction and distinct micellization end points. Macromolecules, 42, 3823, 2009. 

Zhong, X.F., Varshnay, S.K., and Eisenberg, A. (1992) Critical micelle lengths for ionic blocks in solutions of polystyrene-b-poly(sodium acrylate) ionomers. Macromolecules, 25,7160-7167. 

Sha et al. applied the commercially available dual initiator ATRP-4 for the chemoenzymatic synthesis of block copolymers. In a first series of publications, the group reported the successful synthesis of a block copolymer comprising PCL and polystyrene (PS) blocks [31, 32]. This concept was then further applied for the chemoenzymatic synthesis of amphiphilic block copolymers by macroinitiation of glycidyl methacrylate (GMA) from the ATRP functional PCL [33]. This procedure yielded well-defined block copolymers, which formed micelles in aqueous solution. Sha et al. were also the first to apply the dual enzyme/ATRP initiator concept to an enzymatic polycondensation of 10-hydroxydecanoic acid [34]. This concept was then extended to the ATRP of GMA and the formation of vesicles from the corresponding block copolymer [35]. 

Table II presents the experimental data, obtained from using bulk solutions of different NP-EO q/SDS ratios. Figure 6 shows the surfactant composition on the polystyrene latex surface as a function of the surfactant composition in the bulk solution at concentrations corresponding to the onset of micellization. If the surfactant composition on the surface were the same as that in the bulk solution, the experimental points would fall on the dashed line in the figure. Thus, the...

Platonova et al. reported a preparation method of Co nanoparticles having good dispersibility using block copolymer (polystyrene poly-4-vinyl piridine) mi-cells where Co was generated by the reduction of micells loaded with CoCl2 and by thermal decomposition of Co2(CO)s in micellar solutions of the block copolymers... 

Au NPs have been synthesized in polymeric micelles composed of amphiphilic block copolymers. Poly(styrene)-block-poly(2-vinylpyridine) in toluene has been used as nanocompartments loaded with a defined amount of HAuCl4 and reduced with anhydrous hydrazine. The metal ions can be reduced in such a way that exactly one Au NP is formed in each micelle, where each particle is of equal size between 1 and 15 nm [113]. In another example, the addition of HAuCfi to the triblock copolymer (PS-b-P2VP-b-PEO) (polystyrene-block-poly-2-vinyl pyridine-block-polyethylene oxide) permits the synthesis of Au N Ps using two different routes, such as the reduction of AuC14 by electron irradiation during observation or by addition of an excess of aqueous NaBH4 solution [114]. 

Because the essentials of micellization have been discussed in depth for poly(oxyethylene)-containing block copolymers, we do not describe experimental studies on styrenic block copolymers in solution in great detail. Instead, the features are summarized in tabular form (see Tables 3.1-3.4). Experiments on ionic block copolymers containing polystyrene are discussed in Section 3.6.2. 

Gohy et al. studied the solution properties of micelles formed by two polystyrene-frZock-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP- -PEO) copolymers in water by dynamic light scattering and transmission electron microscopy [92]. Spherical micelles were observed that consist of a PS core, a P2VP shell and a PEO corona. The characteristic sizes of core, shell and corona were found to depend on the copolymer composition. The micellar size increased at pH<5 due to P2VP block protonation (Fig. 19). 

Janus micelles are non-centrosymmetric, surface-compartmentalized nanoparticles, in which a cross-linked core is surrounded by two different corona hemispheres. Their intrinsic amphiphilicity leads to the collapse of one hemisphere in a selective solvent, followed by self-assembly into higher ordered superstructures. Recently, the synthesis of such structures was achieved by crosslinking of the center block of ABC triblock copolymers in the bulk state, using a morphology where the B block forms spheres between lamellae of the A and C blocks [95, 96]. In solution, Janus micelles with polystyrene (PS) and poly(methyl methacrylate) (PMMA) half-coronas around a crosslinked polybutadiene (PB) core aggregate to larger entities with a sharp size distribution, which can be considered as supermicelles (Fig. 20). They coexist with single Janus micelles (unimers) both in THF solution and on silicon and water surfaces [95, 97]. 

For polymer chemists it is interesting to know how well-known linear polymers can be linked with dendritic architectures and what the supramolecular consequences of this approach might be. Combination of dendrimers with linear polymers in hybrid linear-dendritic block copolymers has been employed to achieve particular self-assembly effects. Block copolymers with a linear polyethylene oxide block and dendritic polybenzylether block form large micellar structures in solution that depend on the size (i.e., the generation) of the dendritic block [10]. Amphiphilic block copolymers have been prepared by the combination of a linear, apolar polystyrene chain with a polar, hydrophilic poly(propylene imine) dendrimer [11] as well as PEO with Boc-substituted poly-a, -L-lysine dendrimers, respectively [12]. Such block copolymers form large spherical and cylindrical micelles in solution and have been described as superamphi-philes and hydra-amphiphiles , respectively. 

---