PS-6-PEO

In order to improve the tribological properties of molecular films, molecular surface modification is the first choice to make an approach. A Diblock polymer polystyrene-poly(ethylene)oxide (PS-PEO) thin-films were studied in our previous research because of its interesting structure (one... 

The loss of phase complexity in both systems may be attributed to an increase of the PS/PEO and PI/PEO interaction parameters. Because LiClC is selectively located in the PEO domains, the interaction parameters (/ps-peo and xpi-peo ) must increase, leading to variations in domain type and dimension. As the lithium salt increases the polarity (and presumably the solubility parameters) of the PEO domains, the interfacial tensions between PEO and PI, and PEO and PS are elevated. Thus, a reduction in the overall PEO interfacial area is required, which necessitates additional chain stretching. In consequence, the CSC structure becomes dominant when comparing doped and non-doped samples [171] (Figs. 54 and 55b). 

The more recently developed cryo-TEM technique has started to be used with increasing frequency for block copolymer micelle characterization in aqueous solution, as illustrated by the reports of Esselink and coworkers [49], Lam et al. [50], and Talmon et al. [51]. It has the advantage that it allows for direct observation of micelles in a glassy water phase and accordingly determines the characteristic dimensions of both the core and swollen corona provided that a sufficient electronic contrast is observed between these two domains. Very recent studies on core-shell structure in block copolymer micelles as visualized by the cryo-TEM technique have been reported by Talmon et al. [52] and Forster and coworkers [53]. In a very recent investigation, cryo-TEM was used to characterize aqueous micelles from metallosupramolecular copolymers (see Sect. 7.5 for further details) containing PS and PEO blocks. The results were compared to the covalent PS-PEO counterpart [54]. Figure 5 shows a typical cryo-TEM picture of both types of micelles. 

Similar fluorescence techniques have been used by other authors on micelles containing PS cores. In this respect, Riess and Hurtrez showed that no chains were exchanged for PS-PEO micelles, even for rather low PS MW [69]. 

PS-PEO reverse spherical micelles have been used as nanoreactors for the synthesis of metallic nanoparticles, as shown by the works of Moller and coworkers [102] and Bronstein et al. [103]. 

Finally, the formation of crew-cut micelles with spherical and various other morphologies was reported by Eisenberg and coworkers for PS-PEO diblocks with a major PS block [134], More information about crew-cut micelles will be given in Sect. 6. 

Clustering in PS-[Ru]-PEO micelles was shown to be sensitive to temperature and ionic strength, as previously observed for covalent PS-PEO copolymer [131]. These effects were, however, more pronounced in the case of the metallosupramolecular copolymers, indicating a possible influence of the charged fois-2,2/ 6/,2/terpyridine-ruthenium(II) complexes [329]. 

Fig. 11 AFM image of a 260 nm thick film of PS-PEO cast from benzene in a benzene/ water atmosphere for 48 h. Reproduced from [44]...

Another class of polymers capable of stabilizing Au NPs through physisorption is amphiphilic block copolymers. Initial reports describe the formation of Au NPs in the presence of different amounts of diblock copolymers like PS-P2VP (polystyrene-block -poly-2-vinylpyridine) [111] or PS-PEO (polystyrene-block-polyethyleneoxide) [112]. 

Xu et al. (1992) used light scattering to characterize micelles formed by a wide range of PS-PEO di- and tri-block copolymers in dilute solution in water. Although full analysis of the data was complicated by the tendency of the micelles to undergo secondary association, they did find that the micellar radius scaled as eqn 3.14, in agreement with the predictions of Halperin (1987). With values of p and RB from the star-like micelle model, Xu et al. (1992) were able to compute % parameters for the interactions of PEiO with water and with PS, in... 

PS-PEO diblocks adsorbed on glass plates. Adsorption from toluene led to preferential adsorption of PEO however, due to the very high asymmetry of the copolymers studied, and the favourable adsorption energy, PS was also adsorbed. On the approach of a second coated plate, the PS volume fraction increased near the interface, indicative of strong interlayer repulsion (Cosgrove et al. 1994). 

Fig. 3.38 (a) Neutron reflectivity profile for a PS-PEO diblock (M = 15 kg mol-1,1.5% PEO) end-adsorbed from d-toluene onto quartz (Field et al. 1992a). The symbols indicate measured values, whilst the full line is a fit to a parabolic volume fraction profile, (b) Models for the density profile. The parabolic function was found to give the best fit to the data. 

Poly (ethy lene oxide)/poly (styrene) block copolymers A comprehensive study of crystallization from solution in PS-PEO diblocks was performed in the late 1960s and early 1970s (Gervais and Gallol 1973a,b Lotz and Kovacs 1966 Lotz et al. 1966). 

Fig. 5.24 Transmission electron micrograph of crystals (etched with ethanol) formed by a PS-PEO diblock (Mn = 34.1 kg mol-1, 66wt% PS) crystallized from solution in xylene (Lotz et al. 1996).

Fig. 5.25 Phase diagrams for PS-PEO diblocks in diethyl phthalate (Ciervais and Gallot 1973a), a selective solvent for PS. SEO-3 M = 34.7kgmol 59% PEO.This sample forms a non-crystalline lamellar phase (lam) and a lamellar crystalline phase (crystal). SEO-9 Ma - 75 kg mol-1, 70.5% PEO. This sample forms a non-crystalline hexagonal-packed cylinder phase (hex) and a crystal phase.

Fig. 5.26 Showing regions of stability of crystals with different numbers of folds n in the crystallization temperature-concentration plane for a PS-PEO diblock ( Af = 9 kg mol 61% PEO) in diethyl phthalate (Gervais and Gallot 1973a).

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