Polymer surface nitrogenization

When the DMAEMA content of NVP - DMAEMA copolymers was reduced from 20% to 8%, the silica fines stabilization effectiveness appeared to improve slightly. When the 80/20 NVP - DMAEMA copolymer was converted to a terpolymer containing 8% DMAEMA (CH SO, silica fines stabilization was substantially unaffected. However, stabilization of silica/kaolinite fines was greatly improved. This suggested that the interaction of polymer quaternary nitrogen atoms with anionic sites on mineral surfaces was important for the stabilization of migrating clays but a different interaction was important for the stabilization of silica fines. Calcite fines stabilization improved while hematite fines stabilization effectiveness decreased. This also indicated the nature of the adsorbed polymer - fine particle complex varied for different minerals. 

However, the fact that industrial applications of polymer surface fluorination employ a fluorine/nitrogen mixture as the fluorinating agent complicates matters because fluorine gas is toxic, may explode when brought into contact with organic substances, and causes severe bums on human tissue. Moreover, the use of fluorine requires highly qualified personnel and special safety systems. 

A great deal of research has been focused on the evaluation of plasma polymers and plasma treated materials for blood and soft tissue contacting-applications (2,3). A number of studies have involved the physical adsorption or covalent attachment of a variety of biomolecules to various gas plasma-treated polymer surfaces (4,5). In such studies, however, the covalent immobilization is often assumed to take place through precursor groups formed at the biomaterial surface from ill-defined oxygen and nitrogen functionalities obtained directly from the plasma. 

Cordes and co-workers 191 found that the alkaline hydrolysis of p-nitrophenyl hexanoate is subject to catalysis by polyvinylpyridine-based polysoaps. For example, k bs is increased from 0.1 mm to 1.4 mm in the presence of 5 x 10 7 M 38% polysoap (23) (the same material used in the Strauss work). With 5 x 10-7 M polymer having a 15 % dodecyl content, the rate is increased only 3 times above background. The simplest rationale for the kinetics invokes both hydrophobic and electrostatic forces. Thus, dodecyl chains on the polymer hydrophobically bind p-nitrophenyl hexanoate to the polymer surface. Since the polymer possesses a high density of cationic nitrogens, hydroxide ions also accumulate at the polymer surface where they catalyze the hydrolysis of bound ester. Addition of nitrate ion to the aqueous reaction... 

In this review, some of the electroactive polymers most commonly studied during the past one and a half decades have been selected to illustrate the type and level of information obtainable from XPS core-level spectra. It concerns (a) the intrinsic structure, (b) the CT interaction, and (c) the stability and degradation behavior. The review is meant to be comprehensive, although emphasis has been placed on some specific issues related to these three basic physicochemical properties. For example, the chemical nature of the nitrogens in PPY and PAN has been critically compared on the basis of XPS data. Some of the major discrepancies in the XPS literature of electroactive polymers have also been examined. In most cases, preference has been given to results for which proper justification and careful comparison with available data are possible. Finally, some future trends in the application of XPS and other more surface sensitive techniques to the study of highly reactive conjugated polymer surfaces have been mentioned. 

The surface wettability by water drops has been clearly linked with the concentration of chemically bound nitrogen in the surface. Conversely, measurements of advancing and receding contact angles for water can provide information regarding surface composition. On the other hand, there appears to be little or no direct correlation between water wettability and adhesive strength of evaporated aluminum films. Substantial improvement in adhesion of Ai to many polymers can be achieved by 02 plasma treatment of the polymer surface before metallization. Other workers have shown this to result in chemical linkages between the metal and polymer surface moieties. 

Four years later. Stem and co-workers (18) investigated commercial desalination CA membranes with an acetyl-content of 40.8Z. The membranes were dried by a simple method developed by Vos and Burris (19) first soaking them In an aqueous solution containing surfactants to reduce the water-polymer surface tensions, and then alr-drylng theny The nitrogen permeation rate of such a membrane was 4.7 x 10 cm" (STP)/cm -s-cmHg at 30 C... 

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