Polymeric “smart” coatings have been developed that are capable of both detecting and removing hazardous nuclear and heavy metal contaminants from contaminated surfaces. These coatings consist of strippable polymeric compositions containing blends of polymers, copolymers and additives that can be brushed or sprayed onto a surface as a solution or dispersion in aqueous media. Upon drying, these coatings form strong films that can easily be peeled or stripped from the surface. When applied to a contaminated surface, these coatings display responsive behavior. Areas of contamination are indicated by a color change. As the coatings dry, the contaminants are drawn into and fixed in the polymer matrix. Subsequent removal of the coating with entrapped contaminants results in some degree of surface decontamination. Here we report the development and investigation of a smart, decontaminating coating developed for uranium and plutonium.
A new approach to prepare surface-functionalized polypropylene using block cooligomers of propylene and acrylate esters is described. Using boron-promoted radical polymerization and a vinyl-terminated polypropylene oligomer, block cooligomers of propylene and tert-butyl acrylate were prepared. Codissolution of such cooligomers with excess isotactic polypropylene and film casting produced functionalized films. Acidolysis of the tert-butyl esters at the surface of these films produced a poly(acrylic acid)-grafted polypropylene film that could be further modified chemically. Incorporation of pH-sensitive dyes into this poly(acrylic acid) surface in turn produced films whose reactivity in proton-transfer chemistry in various solvent suspensions was studied as a function of solvent.
The effects of solvent on the accessibility and reactivity of an ester-bound fluorophore at a functionalized polyethylene-solvent interface have been studied. Fluorophore-labeled polyethylene surfaces were prepared by blending together a small amount of either a phenylpyrenylmethyl-terminated ethylene oligomer or a pyrene ester-terminated ethylene-ethylene glycol block cooligomer and a 20-200-fold excess of high molecular weight additive-free high-density polyethylene. Solution casting of 1,2dichlorobenzene solutions of these mixtures generated iilms containing the pyrene labels. Studies of the 11/13 values for these films in a series of solvents, studies of the extent of excimer formation, and studies of quenching of the amine fluorescence by soluble amines that are incompatible in bulk high-density polyethylene all suggest that the fluorophores are near or in the solvent-polymer interface. In contrast to soluble pyrene-labeled polymers, the extent of excimer formation for surface-bound pyrene labels was greatest with good solvents. Short grafts where the pyrene label was attached either at the graft origin or at the graft terminus produced significantly different behavior for the pyrene fluorophore label.Surface modification of polymers is important technologically and as a fundamental research p r~b l e m . l -~ Such chemistry has received increasing attention in the last few years because of the potential of such chemistry. For example, surface modification of polymers is often carried out to affect properties like permeability or a d h e~i o n .~,~ Polymer surface chemistry also affects a polymer's hydrophilicity and bio~ompatibility.~~~ In this paper, we describe ways pyrene labels can be used to study solvation changes that occur a t surface-functionalized polyethylenes.It is well recognized that the chemistry of functional groups located at polymer surfaces can be influenced by the medium the functional groups encounter a t the polymer-solvent interface. It is also becoming increasingly apparent that the term "surface" with respect to an organic polymer is a m b i g u o u~.~+~ The definition of what constitutes the "surface" of an insoluble but swellable polymer like polyethylene depends largely on the phenomena one chooses to study and on the experimental conditions of the determination. For example, water contact angles respond to functional groups in the top 5 8, of an otherwise hydrophobic polymer or hydrophobic substrate.1° X-ray photoelectron spectroscopy (XPS) detects groups in the outermost 50-100 8, of a surface.11J2 However, both of these assays involve chemistry where relatively well-defined phase boundaries are present. The situation is less clear for an organic polymer suspended in an organic solvent. For a polymer film suspended in a solvent, we would define the polymer surface as consisting of a solvent-polymer interfacial region where bound functional groups can interact with solvent or reagents in solution. The depth of this interface would depend on how the solvent interacts with the pol...
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