Water contact angles, polymer

Such polymers are as hydrophobic as poly(tetrafluoroethylene) (Teflon), with water contact angles in the range of 107°. But, unlike Teflon, polyphosphazenes of this type are easy to fabricate, are flexible or elastomeric, and can be used as coatings for other materials. ... 

The cast films ofpoly(azomethine)s are transparent but pale to deep yellow in color. The water contact angles of fluorine-containing poly(azomethine)s films from diamine (17) are 80° for terephthalaldehye (19) and 75° for isophthalalde-hyde (20) as dialdehyde component (Table 9.9).20 These low values of water contact angles are attributed to the lower fluorine content in these polymers. 

Problems of desorption and loss of activity encountered with natural heparin have led numerous workers to explore synthetic heparin-like polymers or heparinoids, as reviewed by Gebelein and Murphy [475, 514, 515]. The blood compatibility of 5% blended polyelectrolyte/polyfvinly alcohol) membranes was studied by Aleyamma and Sharma [516,517]. The membranes were modified with synthetic heparinoid polyelectrolytes, and surface properties (platelet adhesion, water contact angle, protein adsorption) and bulk properties such as permeability and mechanical characteristics were evaluated. The blended membrane had a lower tendency to adhere platelets than standard cellulose membranes and were useful as dialysis grade materials. 

After natural ageing, again an increase in the water contact angle, was observed. However, the values of the untreated polymer surface were never reached. 

There are two methods for rendering a polymer surface slippery. One is to make the polymer surface either very hydrophobic or very hydrophilic. From a practical point of view, an extremely hydrophilic polymer surface is more attainable than an extremely hydrophobic one, because the water contact angle of even the most hydrophobic surface currently available is not larger... 

The effect of the thickness of plasma polymer of CH4 on the contact angles of water is summarized in Table 29.6, and the results of XPS analysis are summarized in Table 29.7. The trend in the decrease of water contact angle on immersion seen for... 

Figure 32.20 Water contact angle change of closed system and flow system TMS polymer surfaces with the power input of argon and oxygen plasma posttreatment.

It can be seen that the second Ar or O2 plasma treatment lowered the water contact angles on closed system TMS polymer surfaces, but not as much as the change introduced on the flow system sample. 

At higher treatment temperatures, differences between the water contact angles of the polymers are small, but at even higher temperatures, the hydrophobicity of poly(octadecylmethylsiloxane) declines more rapidly than that of poly(diethylsiloxane) and PDMS because of the poorer thermal stability of siloxanes with higher alkyl substituents. Despite this defect, some-... 

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