Polymer deposition technologies

As mentioned earlier, it is misleading to describe advances in the properties of polymers without also describing how such polymers are processed into thin films or crystals. Moreover, many of the physical properties of polymers are inextricably linked to their structural and orientational order. An excellent example of this is the piezoelectric and pyroelectric coefficients of the well-known polymer, polyvinylidene difluoride (PVdF) 

The polymer solution flows radially outwards to form a thin solution layer that subsequently sets as the solvent evaporates. The uniformity of the layer depends on a number of factors including the initial acceleration of the substrate and the rate of solvent evaporation, both of which can be easily controlled. The film thickness, d, depends on the solution viscosity, Tj, rotation speed 0, solution density p and spiiming time t and is given by  

More involved models to relate the thickness to the spinning conditions have been developed [36]. Generally, the polymer molecules within spin-coated films are relatively disordered and order has to be induced after deposition via stretch aligning or more commonly via electrical poling at elevated temperature [37]. 

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Photo-resist technology is widely used for imaging processes in such applications in electronics. If it is wished to produce a metallic pattern of connections between many electronic components (resistors, capacitors, integrated circuits, etc.), this can be done by the selective etching of a thin copper plate deposited on an insulating base. The copper layer is protected by a resist which is a polymer, deposited in such a way that it prevents the attack of the metal by an etching solution which will solubilize only the unprotected, exposed copper (Figure 6.8). 

Several techniques are applicable to bulk polymer materials, such as vacuum deposition technologies. Vacuum deposition processes may be used to obtain thin polymer films that have high density, thermal stability, and insolubility in organic solvents, acids, and alkalis. These polymer deposition techniques involve in situ polymerization on a substrate surface affected by various factors. The layers can be deposited on any substrates that cannot be damaged by the vacuum processes. The following are all examples of vacuum deposition processes (Skolheim 1986 Harsanyi 20(X)) ... 

A unique feature of in situ encapsulation technology is that polymerization occurs ia the aqueous phase thereby produciag a condensation product that deposits on the surface of the dispersed core material where polymerization continues. This ultimately produces a water-iasoluble, highly cross-linked polymer capsule shell. The polymerization chemistry occurs entirely on the aqueous phase side of the iaterface, so reactive agents do not have to be dissolved ia the core material. The process has been commercialized and produces a range of commercial capsules. 

The group in the Swiss Federal Institute of Technology [55] has fabricated a macroscale device by depositing the conducting polymer (poly(/j-phenylenevinylene)) on the MWCNT film (Fig. 16). They have observed the characteristic rectifying effect from the l-V curve, which suggests the CNTs inject holes efficiently into the polymer layer. However, due to the difficulty in... 

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