Ag-PEO

Figure 9. Schematic representation of the asymmetric plasma reactor used for the PEO-like and Ag/PEO-like coating deposition.18...

As determined by XPS analysis, the surface composition and O/C and N/C elemental ratios for 5 W and 15 W PEO-like and Ag/PEO-like films, following incubation in the protein solutions are illustrated in Table 1 for a power of 5 W. The data (Table 1) demonstrate that the PEO-like coatings are effective at reducing and/or preventing protein adsorption. The PEO-like films completely prevented the adsorption of albumin, as XPS did not detect a nitrogen signal. Moreover, the O/C ratio of the film is maintained after albumin exposure. 

Table 1. Atomic percentages for the 5 W PEO-like and Ag/PEO-like films, following incubation in the protein solutions, bovine serum albumin and fibrinogen. In this figure BSA represents bovine serum albumin and F represents fibrinogen.18...

The analysis of these experimental data, taken from reference [28], shows that the thermodynamic parameter values of IC and PEO are completely different. A large positive AH0 and also a large positive AS° are found for the adsorption process of PEO, suggesting that the driving force for this process is of an entropic nature and then AG° is more negative when the temperature increases. 

This section summarizes some of the most significant electrochemical results obtained to date for selected electrodes cleaned and characterized under UHV in PEO-lithium-based solutions, and include nonalloy (Ni)- and alloy-forming metals (Ag and Al), a noninteracting substrate (boron-doped diamond, BDD) and a material capable of intercalating Li+ (graphite). It is expected that the information herein contained will serve to illustrate the power of this methodology for the study of highly reactive interfaces. 

FIGURE 13.5 Difference pair correlation functions AG(rz) between the atomic pair correlation functions of samples with deuterated and hydrogenous PEO. In the case of the 0.1 M salt concentration (solid line), the butylammonium chains were deuterated in both samples, whereas for the 0.03 M salt concentration (dashed line), both samples contained hydrogenous counterions. The volume fraction of PEO was 4% in all cases. 

From these absorbance changes, the repetition of the redox response of PEO-cyt.c was also observed in situ followed by the potential sweep. Figure 13.2 shows the absorbance change at 414 nm induced by the potential sweeping (sweep rate 5 mV/s, potential sweep range between —0.8 and +0.8 V vs. Ag). The stable absorbance change due to the redox reaction of PEO-cyt.c was observed without attenuation. 

The corresponding AG(r) is shown in figure 2. A clear peak is observed at 1.1 A which corresponds to the characteristic C-H bond distance and coordination number in the polymer. It is clear that there is no strong structure at larger distances in the first order difference. This is largely due to the fact that the polymeric hydrogen is not at any particular centre of symmetry in relation to the hydrating water. However it is possible to reveal more of the hydration structure after the (known) intermolecular structure of the PEO molecule is subtracted firom the difference function. A detailed analysis of the result after this subtraction. 

The molecules of a block copolymer can micellize in an aqueous solution. A well-known example is Pluronic F127, a PEO-PPO-PEO block-copolymer from BASF AG, Germany. This polymer is cross-linkable by irradiation and, therefore, the micelles formed in aqueous solution can be fixed by irradiation. 

Fabrication of well-arranged metal nanoparticle arrays by using nanocylinder structured template films is one of the important topics in nanotechnology. The size and the periodicity of the nanoparticle arrays can be controlled independently by choosing appropriate templates. This control has been achieved by using well-ordered nanotemplate films of PEO-based azo LCBCs (Li et al., 2007b). As shown in Fig. 12.21, a well-ordered array of Ag nanoparticles was fabricated successfully... 

Interestingly, Smeenk et al. could realize similar structures with a protein-polymer conjugate. For that purpose, a central high-molecular-weight p-sheet-tum protein (poly[(AG)3EG] with n = 10 or 20) was flanked on both terminal sides with PEO blocks. The resulting PEO-protein ABA conjugate shows self-assembly into well-defined fibrils with a protein p-sheet core with a distinct fine stmcture and PEO shell. 

NaBHa was used as reducing agent in a solution of AgNOs and chitosan in acetic acid to obtain Ag NPs. In this case, PEO was added to the solution in order to improve the spinnability of chitosan [76]. 

PEO 2000 for synthesis (Merck-Schuchardt) was chosen for osmotic vapour pressure measurements. Fructose p.a. (Fa. Merck) was used as calibrating substance. For the membrane osmosis PEO 35000 (Hoechst AG) was taken. This product was fractionated by slowly cooling a solution (10 wt.% PEO) of a mixture water/acetone (15/85 wt./wt.). This procedure was carried out to make sure, that the sample doesn t contain portions of low molecular polymers <20000 g/mol. The membranes (Sartorius, Gottingen, regenerated cellulose Cat.-Nr. 11539) have a lower limit for determination of molar masses of 20000 g/mol. 

Other materials have been used to cationize the pol5miers. Metallocenes (ferrocene, nickelocene, and cobaltocene) have been used as cationizing agents for polystyrene and PEO (47). These cations have the advantage that they are soluble in many organic solvents and also do not have the isotopic splitting seen with Ag, which often complicates the interpretation of the MALDI spectra. 

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