Poly metal/polymer interfaces

When rfc = 0, the polymeric structure is considered to be open enough (i = 0) that any subsequent oxidation will not occur under conformational relaxation control, hence P = 1. Every polymeric chain at the poly-mer/solution interface acts as a nucleus a planar oxidation front is formed that advances from the solution interface toward the metal/polymer interface at the diffusion rate. 

On the other hand, Doblhofer218 has pointed out that since conducting polymer films are solvated and contain mobile ions, the potential drop occurs primarily at the metal/polymer interface. As with a redox polymer, electrons move across the film because of concentration gradients of oxidized and reduced sites, and redox processes involving solution species occur as bimolecular reactions with polymer redox sites at the polymer/solution interface. This model was found to be consistent with data for the reduction and oxidation of a variety of species at poly(7V-methylpyrrole). This polymer has a relatively low maximum conductivity (10-6 - 10 5 S cm"1) and was only partially oxidized in the mediation experiments, which may explain why it behaved more like a redox polymer than a typical conducting polymer. 

Coated-wire electrode — A polymer film containing an ion-responsive material and a binder, e.g., poly(vinyl)chloride, is coated onto a conductor (e.g., a metal wire or graphite). They show useful response to solution concentrations of measured species in the range 10-5 < c < 0.1 mol dm-3. The processes at the metal polymer interface are still not understood. 

Metal polymer interfaces chromium coated poly(ethylene terephthalate) (PET) (26) and metalized polycarbonate (PC)(27)... 

We consider the polymer to have a significant ion concentration. Thus an electrical double layer will form at the Me/poly interface, leading to capacitive charging current (mechanism a). Second, in dynamic measurements the current associated with the oxidation/reduc-tion of the polymer redox sites P /P (mechanism b) is often very large. Third, it should be noted that the reaction 0/R may proceed as a regular electrochemical charge transfer reaction at the metal/polymer interface. This was found to be the main mechanism in several systems, e.g., H2/H on polypyrrole-coated metal electrodes [235.246]. 

One way to overcome the problem of chirality existing only at the metal-matrix interface is to encase the metal particle inside the chiral matrix. In that case, all of the metal surface atoms should be close to a chiral center however, this approach has some problems too. For example, access to the metal surface may be inhibited by the encasing matrix. In spite of this, several attempts have produced moderately successful catalysts by creating metal—polymer catalysts. Pd has been deposited on poly-(5)-leucine (Scheme 3.4) and Pd and Pt colloids have been encased in a polysaccharide to produce catalysts that enanti-oselectively hydrogenated prochiral C=C and C=N bonds (Scheme 3.5).7... 

According to the theory of metastable adsorption of de Gennes [216], when an adsorbed polymer layer is in contact with a pure solvent, the layer density diminishes with increasing distance to the srrbstrate (e g., metal) sirrface. The behaviors of several polymer film electrodes, such as poly(tetracyanoqirinodimethane) [133], poly(vinylferrocene) [148,217], polypyrrole [218] and polyaniline [69,219], have been explained by asstrming that the local film density decreases with film thickness that is, from the metal strrface to the poly mer solution interface. 

In failure analysis the possibility to record all elements is advantageous, not least in combination with 3D imaging (i.e., a TOF-SIMS instrument with dual-beam capability is the instrument of choice). An example is the investigation of black spots in OLEDs where a fluorine-based polymer was sandwiched between a metallic cathode consisting of Ba and A1 and a poly(3,4-ethylenedioxythiophene)/ITO anode. From the recorded raw data, depth profiles can be reconstructed as well as two-dimensional (2D) images in any depth or a 3D representation of all interesting signals. It was found that aluminum was oxidized at the Al/polymer interface [220]. 

When addressing the adhesion of polymers to interfacing materials, the primary and foremost challenge is to understand the fundamental driving forces which can initiate the development of adhesion strength between polymer-to-polymer, poly-mer-to-metal, polymer-to-ceramic, or polymer-to-inks coatings and adhesives. These interfaces also exist in multivariate environments, such as heat and humidity, which also must be examined. Ultimately, it is the polymer and the interface chemistry that determine adhesion. However, there can be adhesion failure between the polymer and an inorganic, such as a metal, due to an oxide layer that is weakly attached. 

Polymer electrolytes (e.g., poly (ethylene oxide), poly(propylene oxide)) have attracted considerable attention for batteries in recent years. These polymers form complexes with a variety of alkali metal salts to produce ionic conductors that serve as solid electrolytes. Their use in batteries is still limited due to poor electrode/electrolyte interface and poor room temperature ionic conductivity. Because of the rigid structure, they can also serve as the separator. Polymer electrolytes are discussed briefly in section 6.2. 

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