PEO, brushes

Fig. 10 Plots of Le/f-cw vs. dimensionless graft density a (1) PS brushes prepared by adsorption of PS-polydimethylsiloxane block copolymers (Mw,ps = 60000) and 0 (Mw,ps = 169000) [21,22]. (2) PEO brushes prepared by adsorption of PEO-PS block copolymers A (Mw.peo = 30800) and V (Mw.peo = 19600) [201]. (3) PMMA brushes prepared by surface-initiated ATRP (M = 31 300 267400). Data reprocessed from [116,117]...

Fig. 17 Dependence of the average PEO brush height ((Jj)brush) on the surface area per grafted chain (s), where (/i)brush was calculated by two different methods. The squares represent (h)brush from the difference between the average radii of the PNIPAM microgels with and without the grafted PEO chains and the circles from the ratio of / [70]...

Fig. 18 Grafting density (a) dependence of average PEO brush height ((h)brush) during the PEO chain stretching. The line represents a least square fitting of (h)brUsh

Adhesion data are presented in Figure 6. The adhesion of S. epidermidis is suppressed to essentially zero by each of the PEO brushes investigated. However, for P. aeruginosa adhesion is only slightly reduced at the short brush. 

Figure 6. Effect of PEO brushes on the adhesion of micro-organisms at glass surfaces at 20°C (white bars) and 37°C (black bars). For further details refer to the text.

Three main trends emerge from the data presented in Figure 6 (1). For both types of microbes, the bacteria and the yeasts, the adhesion of the hydrophobic cells is less strongly reduced. Apparently, hydrophobic interaction favours PEO-cell interaction. (2) The PEO brushes are less effective in repelling the... 

Protein adsorption on PEO brushes has been extensively studied and has recently been reviewed [48], In general, PEO brushes greatly reduce and sometimes even completely prevent protein adsorption. Easy removal of proteins from PEO coatings has also been described [49,50],... 

At higher pressure some positive component outweighs the double layer repulsion. It might be speculated that this strong repulsion is due to steric interactions between the hydrophilic PEO brushes and (at least) three surface force components must be considered, i.e. n = n vw + n ei + rrst. 

Figure 3.99. Simplified sketch of a PEO brush consisting of trains at the surface (with flj. close to unity) and a brush region of volume fraction 0 and thickness H.

Figure 80 Temperature dependencies of conductivities for PEO brushes with short side chains (MW = 300g moi ) at various UCF3SO3 doping levels (symbols are experimental data lines are fits with the Vogel-Fulcher-Tammann equation). The vertical dashed line indicates the range of room temperature (295 K). Reprinted from Zhang, Y. ...

UF PAN membranes. The coated membranes were immersed in isopropanol for 30 min and thereafter in a water bath. It was shown that during precipitation, the copolymer undergoes microphase separation, forming interpenetrating networks of PAN-rich and PEO-rich nanodomains. Transmission electron microscopy reveals that PEO domains act as water-permeable nanochannels and provide the size-based separation capability of the membrane. A small decline in flux (15%) was observed in a 24 h dead-end filtration experiment with 1 g/1 BSA solution using the modified membrane, while the base UF membrane lost 81% of its flux irreversibly in the same conditions. It was concluded that the PEO brush layer, formed on the membrane surface, acts as a steric barrier to protein adsorption, endowing these membranes with exceptional fouling resistance. 

FIGURE 20.8 Micrographs of (a) Staphylococcus epidermidis and (b) Candida albicans around the border zone between glass (left-hand side) and PEO brush-coated glass (right-hand side). Bars 10 om (a) and 40 pm (b). (Adapted from Roosjen, A. et al. Microbiology 149 3229, 2003.)... 

Sufficiently dense brushes are also able to prevent adsorption of globular proteins to surfaees. An example is given in Figure 20.9 for the adsorption of blood proteins on polystyrene surfaces coated with a PEO brush. The arrow in Figure 20.9 indicates the amount of plasma proteins adsorbed on the bare polystyrene surface. The enhanced protein adsorption on the less dense brushes suggests (weak) attraction... 

FIGURE 20.9 Adsorption of proteins from human blood plasma on a PEO brush-coated polystyrene (PS) surface as a function of the (reciprocal) PEO grafting density. (Adapted from Norde, W. and Gage, R.A. Langmuir 20, 4162, 2004.)... 

Subsequently, Wolf and coworkers [49] investigated the effect of copolymer architecture on the interfacial tension reduction for the PDMS/PEO blend utilizing PDMS-h-PEO diblocks, PDMS-b-PEO-b-PDMS triblocks, and bottle-brush copolymers consisting of PDMS backbone and PEO brushes. The study showed that for the range of molecular weights investigated, the total number of PDMS... 

It is suspected that the PEO brush layer formed on the internal pore surface by Pluronic F127 and F108 might reduce the appar-... 

As shown above, it has been known for some time that the solubility of polyelectrolytes in aqueous media can be influenced by the electrochemical switching of the counterions. However, this principle has only recently been applied to trigger electrochemically built-up micellar aggregates from unimolecular solutions by adjusting the solubility of one part of a binary block-like copolymer [235]. Hereby, the electrolysis of ferrocyanide to ferricyanide led to the formation of vesicles (polymersomes). In contrast to real film formation, the solubilizing part, poly (ethylene oxide) (PEO), prevented film deposition on the electrode. Instead, bilayer film formation in bulk solution was favored under vesicle build-up with an insoluble polyelectrolyte complex as the vesicle wall, sandwiched between a well-hydrated PEO brush. 

FIGURE15.10 Illustration of PEO brush layer formation on the surface of membrane internal pores due to the surface segregation of Pluronic. 

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