Polymer film modification

When a polymer film is exposed to a gas or vapour at one side and to vacuum or low pressure at the other, the mechanism generally accepted for the penetrant transport is an activated solution-diffusion model. The gas dissolved in the film surface diffuses through the film by a series of activated steps and evaporates at the lower pressure side. It is clear that both solubility and diffusivity are involved and that the polymer molecular and morphological features will affect the penetrant transport behaviour. Some of the chemical and morphological modification that have been observed for some epoxy-water systems to induce changes of the solubility and diffusivity will be briefly reviewed. 

Laser ablation of polymer films has been extensively investigated, both for application to their surface modification and thin-film deposition and for elucidation of the mechanism [15]. Dopant-induced laser ablation of polymer films has also been investigated [16]. In this technique ablation is induced by excitation not of the target polymer film itself but of a small amount of the photosensitizer doped in the polymer film. When dye molecules are doped site-selectively into the nanoscale microdomain structures of diblock copolymer films, dopant-induced laser ablation is expected to create a change in the morphology of nanoscale structures on the polymer surface. 

As aforementioned, diblock copolymer films have a wide variety of nanosized microphase separation structures such as spheres, cylinders, and lamellae. As described in the above subsection, photofunctional chromophores were able to be doped site-selectively into the nanoscale microdomain structures of the diblock copolymer films, resulting in nanoscale surface morphological change of the doped films. The further modification of the nanostructures is useful for obtaining new functional materials. Hence, in order to create further surface morphological change of the nanoscale microdomain structures, dopant-induced laser ablation is applied to the site-selectively doped diblock polymer films. 

In the last 30 years considerable progress has been made in the development of tailor-made electrode surfaces by chemical modification [4-12] of electrodes surfaces with electroactive polymer films. A comprehensive description of electroactive polymer-modified electrodes can be found in the book edited by M. Lyons [13]. 

Modification of mortar and concrete in the presence of a latex occurs by concurrent cement hydration and formation of a polymer film (coalescence of polymer particles and the polymerization of monomers). Cement... 

Amylose brushes (a layer consisting of polymer chains dangling in a solvent with one end attached to a surface is frequently referred to as a polymer brush) on spherical and planar surfaces can have several advantageous uses, such as detoxification of surfaces etc. The modification of surfaces with thin polymer films is widely used to tailor surface properties such as wettability, biocompatibility, corrosion resistance, and friction [142-144]. The advantage of polymer brushes over other surface modification methods like self-assembled monolayers is their mechanical and chemical robustness, coupled with a high degree of synthetic flexibility towards the introduction of a variety of functional groups. 

Fig. 40. Possible reaction sequence for initial stages of glow discharge modification of polymer films of an ethylene-tetrafluoroethylene copolymer...

REACTIVE GASES AS REAGENTS FOR POLYMER FILMS CHEMICAL MODIFICATIONS... 

K. Allmer, A Hult, and B. Ranby, Surface modification of polymers. III. Grafting of stabilizers onto polymer films, J. Polym. Sci Part A folym. Chem., 27 3405 (1989). 

Rapid polymerization of electrochemically generated species such as organic radicals can cover an electrode with a polymeric film. Such films are sometimes impenetrable and difficult to remove, which results in passivation of the electrode surface. A typical case is the oxidation of 1,2-diaminobenzene [9]. The modification of electrode properties by coating with thin polymer films is currently an area of active investigation [10— 12]. 

Electroanalytical sensors based on amperometric measurements at chemically modified electrodes are in the early stages of development. The modes of modification can take many forms, but the most common approach at the present time is the immobilization of ions and molecules in polymer films which are applied to bare metal, semiconductor, and carbon electrodes. Such surface-modified electrodes exhibit unique electrochemical behavior which has been exploited for a variety of applications. 

Chemical modification of electrode surfaces by polymer films offers the advantages of inherent chemical and physical stability, incorporation of large numbers of electroactive sites, and relatively facile electron transport across the film. Since th% polymer films usually contain the equivalent of one to more than 10 monolayers of electroactive sites, the resulting electrochemical responses are generally larger and thus more easily observed than those of immobilized monomolecular layers. Also, the concentration of sites in the film can be as high as 5 mol/L and may influence the reactivity of the sites because their solvent and ionic environments differ considerably from dilute homogeneous solutions [9]. 

PAMAM]. The final step of this functionalization relied on activation and cross-linking of attached dendrimers with a homobifunctional spacer (DSG or PDITC). Alternatively, after attachment of dendrimers to the surface, glutaric anhydride activated with V-h ydrox vsucc i n i m i de can be used. This surface modification yields a thin, chemically reactive polymer film, which is covalently attached to the glass support and can be directly used for the covalent attachment of amino-modified components, such as DNA or peptides (Fig. 14.2b). 

More recent efforts focused on surface modification of conductive polymers by the SECM, fabrication, and characterization of microstructures. Mandler et al. developed an approach for the formation of a 2D conducting polymer on top of an insulating layer. This approach, based on electrostatically binding a monomer (anilinium ions) to a negatively charged self-assembled monolayer of co-mercaptodecanesulfonate [MDS, HS(CH2)ioS03 ] followed by its electrochemical polymerization. The polyanion monolayer exhibited the properties similar to those of a thin polymer film [167]. 

---