Polymer-substrate surface

Atomic force spectroscopy shows that when only the polymer-substrate surface is modified, parallel orientation of the nanoscopic cylinders is observed in the 137 nm thick film (see Figure 4.34(a)) because of the lower surface energy of the polystyrene block. However, the presence of a random copolymer at both the polymer-substrate and the polymer-air interfaces eliminates the preferential... 

The equilibrium wetting behavior of simple liquids (including low MW polymers) on low polarity polymer surfaces is well documented and consistent with Gibbsian thermodynamics within specific constraints. Empirical relationships have been established between observed contact angles and polymer surface chemical composition. Predictive relationships have been established between contact angles and polymer substrate surface chemistry based on the theory of fractional polarity surface energies can be factored into dispersion and polar components. These relationships seriously break down with increasing polarity of either the liquid or solid surface. 

SIMS is extremely sensitive, even to the part per billion range, and is used widely in the semiconductor industry. SIMS and XPS are complementary since they provide very similar information [203], but the depth resolution of static SIMS is substantially higher than XPS. However, the quantitative use of SIMS in polymer science is currently not as well developed as XPS. SIMS has been used to study the surface of polyurethanes [204,205] and PMMA-S lamellar diblocks [206]. In the latter study, dynamic SIMS was used to show that the lamellae aligned parallel to the surface after annealing. The thickness of the layer nearest the free surface as well as near the polymer-substrate surface... 

Nelea V, Luo L, Demers CN, Antoniou J, Petit A, Lerouge S, et al. Selective inhibition of type X collagen expression in human mesenchymal stem cell differentiation on polymer substrates surface-modified by glow discharge plasma. J Biomed Mater Res A... 

For example, the low-temperature plasma treatment is a technique that does not negatively affect the environment, so that it is widely applied for modifying the polymer substrate surface. The main benefits of this technique are (Kim et al. 2005) ... 

Fig. 1. The hthographic process. A substrate is coated with a photosensitive polymer film called a resist. A mask with transparent and opaque areas directs radiation to preselected regions of the resist film. Depending on resist characteristics, exposed or unexposed portions of the film are removed using a developer solvent. The resulting pattern is then transferred to the substrate surface and the resist is stripped.

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

The distance between the disk surface facing the optics and the memory layer naturally has to be much smaller than in common optical disks, where the memory layer is deposited behind a 1.2-mm thick transparent glass or polymer substrate disk. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

Friedrich et al. also used XPS to investigate the mechanisms responsible for adhesion between evaporated metal films and polymer substrates [28]. They suggested that the products formed at the metal/polymer interface were determined by redox reactions occurring between the metal and polymer. In particular, it was shown that carbonyl groups in polymers could react with chromium. Thus, a layer of chromium that was 0.4 nm in thickness decreased the carbonyl content on the surface of polyethylene terephthalate (PET) or polymethylmethacrylate (PMMA) by about 8% but decreased the carbonyl content on the surface of polycarbonate (PC) by 77%. The C(ls) and 0(ls) spectra of PC before and after evaporation of chromium onto the surface are shown in Fig. 22. Before evaporation of chromium, the C(ls) spectra consisted of two components near 284.6 eV that were assigned to carbon atoms in the benzene rings and in the methyl groups. Two additional... 

Fig. 33. High resolution C(ls) XPS spectra obtained from (A) silver and (B) polymer fracture surfaces of specimens prepared by curing the polyamic acid of PMDA/4-BDAF against polished silver substrates. Reproduced hy permission of the American Chemical Society from Ref. [391.

One of the most common rubber adhesives are the contact adhesives. These adhesives are bonded by a diffusion process in which the adhesive is applied to both surfaces to be joined. To achieve optimum diffusion of polymer chains, two requirements are necessary (1) a high wettability of the adhesive by the smooth or rough substrate surfaces (2) adequate viscosity (in general rheological properties) of the adhesive to penetrate into the voids and roughness of the substrate surfaces. Both requirements can be easily achieved in liquid adhesives. Once the adhesive solution is applied on the surface of the substrate, spontaneous or forced evaporation of the solvent or water must be produced to obtain a dry adhesive film. In most cases, the dry-contact adhesive film contains residual solvent (about 5-10 wt%), which usually acts as a plasticizer. The time necessary... 

The mechanism by which the primers are thought to work is relatively straightforward. The primer first diffuses into the polyolefin surface, and subsequently becomes entangled in the polyolefin. The primer molecule can then act as an anchor in the substrate surface for the adhesive polymer, which forms after the primer initiates polymerization of the alkyl cyanoacrylate monomer [37]. 

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