Surface water sensitive polymers

There are three major complications in contact angle studies of proteins and other water sensitive polymers. First, no simple or safe method of guaranteeing the cleanliness or uniformity of specimen surfaces is available the initial purity of the sample must be relied upon as the primary criterion of surface uniformity. Second, there is a strong effect from adsorbed water molecules which remain on the surface and... 

Surface interactions between water and polymer networks have a profound effect on the water structure. The properties of water in these and other heterogeneous systems are sensitive to the size of the network pores and have been described by the two-phase model which assumes partition of the water between the "bulk and the "bound water phases" Evidence for this partition has been obtained in several proton NMR studies and also in ESR studies of paramagnetic probes in zeolites, silica gels and in water containing polymers. ... 

The emulsifier provides sites for the particle nucleation and stabilizes growing or the final polymer particles. Even though conventional emulsifiers (anionic, cationic, and nonionic) are commonly used in emulsion polymerization, other non-conventional ones are also used they include reactive emulsifiers and amphiphilic macromonomers. Reactive emulsifiers and macromonomers, which are surface active emulsifiers with an unsaturated group, are chemically bound to the surface of polymer particles. This strongly reduces the critical amount of emulsifier needed for stabilization of polymer particles, desorption of emulsifier from particles, formation of distinct emulsifier domains during film formation, and water sensitivity of the latex film. 

Figure 16.7 Sequence of insulin release from pH/temperature-sensitive polymer matrix. Both glucose oxidase and insulin are loaded inside the matrix. The decrease in pH by gluconic acid results in ionization of the polymer, which in turn increases the lower critical solution temperature. This makes the polymer water-soluble, and erosion of the polymer matrix at the surface releases the loaded insulin...

The same plasma polymer deposited in a closed-system reactor has a graded elemental composition with a carbon-rich top surface, and the oligomer content is much lower [10], both of which increase the level of adhesion. The adhesion of the same water-borne primer is excellent and survives 8 h immersion in boiling water. When this surface is treated with O2 plasma, the adhesion does not survive 1 h of boiling, while the dry tape test still remains at the level of 5. The water-sensitivity of adhesion depends on the chemical nature of the top surface as depicted by XPS data shown in Figure 28.12. Water-insensitive tenacious adhesion, coupled with good transport barrier characteristics, provides excellent corrosion protection, as supported by experimental data [1-4], and constitutes the basic principle for the barrier-adhesion approach. 

Applications of FAB have been succesfully performed in the characterization of a wide range of compounds (dyes, surfactants, polymers...) but little attention has been devoted to the capabilities of this technique to solve environmental concerns, such as organic pollutants identification in water. The widespread use of surfactants in the environment has required the emplo yment of both sensitive and specific methods for their determination at trace levels. GC/MS and HPLC procedures has been used for the determination of anionic (LAB s) and non ionic surfactants (NPEO) in water (1-4). Levsen et al (5) identified cationic and anionic sirrfactants in surface water by combined field desorption/ collisionally activated decomposition mass spectrometry (FD/CAD), whereas FAB mass spectrometry has been used for the characterization of pine industrial surfactants (6-8). 

These data are corroborated by results obtained from continuous photolysis experiments. Cabowax-20M protected Pt catalyst when coupled to Ru02 fails to split water under illumination of a cyclic system containing Ru(bipy)3+ as a sensitizer and methylvio-logen as an electron relay. By contrast, if the Pt microspheres are protected by PVP-Ci6 simultaneous H2 and 02 productions are observed. The lack of specificity of the Carbo-wax 20 M protected particles is attributed to the strongly hydrophylic nature of this protective polymer providing facile access of the Ru(bipy)3+ cation to the platinum surface. Uncharged hydrophylic polymers appear thus unsuitable for Pt protection in this cyclic water decomposition system. 

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