Tuesday, January 6, 2015

Selection of conductive polymer Since the discovery of conducting polymers have stability - and thu

Mikromønstring of conductive polymers
Conductive polymers increased stability and conductivity and the improved cell membrane processing methods enables and facilitates the transfer of research objects into actual products. As part of this development has succeeded in mikrostrukturere conductive polymers. Here, there had to be mastered on two main factors: the polymerization process and the binding to the substrate.
Conductive polymers are conjugated cell membrane polymers conjugation, i.e., alternating double and single bonds is a prerequisite for obtaining electronic conductivity in polymers. The first system that was discovered, cell membrane described and later triggered a Nobel Prize [1], was polyacetylene (Figure 1). Undoped trans-polyacetylene (1a and 1b) are semiconducting. When doped structure, i.e., that of example. iodine removed electrons from the conjugated polymer cell membrane chains, there is a positively charged polaron area which can move through cell membrane the string in an applied cell membrane field (1c and 1d). This provides electrical conductivity, which is a billion times higher than in undoped cell membrane trans-polyacetylene. Trans-polyacetylene is the model system all love because. Its relatively simple structure that allows setting of beautiful models for spectroscopic and electrical properties. Polyacetylene best handled in high vacuum (self igniting due. Oxygen-doping), cell membrane and hence the interest now turned towards systems with better chemical properties. It has in particular attempted to produce chemically stable, processable conjugated polymers preferably from aromatic building blocks (Figure cell membrane 2). It is harder to describe these systems characteristics in simple models, but in return has been manageable materials.
Selection of conductive polymer Since the discovery of conducting polymers have stability - and thus the conductivity - over time been one of the major problems. This has limited the actual use where high conductivity cell membrane is essential. Instead, it has been particularly semiconductors that have been most successful (LED, display, etc.). This picture is about to change, cell membrane allowing cell membrane them to produce conductive polymers with high and stable conductivity and reasonable longevity. The change is mainly due to commercial availability of the required monomer 3,4-ethylenedioxythiophene (EDT) (Figure 2) from Bayer AG (Baytron M). EDT's good characteristics due to the dioxyring, which is bonded to the thiophene ring at position 3 and 4, thereby preventing undesired bonding at these positions during the polymerization. Dioxyringen lowers the oxidation potential of the monomer so that the polymerization proceeds more easily than that of thiophene and causes the polymer are oxidized cell membrane (and hence the conductive) at normal temperature. conditions. Finally, cell membrane decreases dioxyringen band gap, so the conductivity is increased compared. Thiophene. One of the prerequisites for achieving good conductive surfaces is that EDT is polymerized, where it will be used by oxidative polymerization. This will enable the conductance 30-100 times higher cell membrane than with the aqueous suspension of the PEDT, which is also commercially available from Bayer AG (under the name of Baytron cell membrane P) [2]. With electrochemical oxidative polymerization and the PEDT is obtained conductivities of up to 550 S / cm [3.4]. The choice of poly (3,4-ethylenedioxythiophene) (PEDT) as conjugated polymer was obvious as micro-patterned conductive polymers in particular was chosen to act as a transporter of energy and signals.
PEDT's polymerisationsveje and weigh Polymerization of EDT can be performed in a variety of ways: Electrochemical. Here the transfer of electric charge to force the necessary oxidation of EDT. The method is highly constrained by the need for an electrically conductive substrate to complete the polymerization of the conductive polymer (and how much fun it is!). Oxidative. Polymerization of using EDT. A chemical oxidizing agent, typically iron (III) - and Cu (II) salts as well as peroxydisulphatforbindelser. Monomer and oxidizing agent are mixed in a solvent (water or an alcohol), and the polymerization proceeds either in the solvent cell membrane (precipitates as precipitate), or by the solution applied to a substrate. cell membrane As the solvent evaporates, EDT polymerizes and forms a conductive film on the substrate. The latter gives a reasonable film, but is not very reproducible and quite impossible to use on a large scale, because the life of the mixture is no more than 10-15 minutes at room temperature. Therefore, we were on the lookout for an alternative method: Dampfasepolymerisation (VPP) of EDT Dampfasepolymerisation (from English: vapor phase polymerization (VPP). A rather misleading term because it really is an oxidative polymerization on a surface where the monomer cell membrane just supplied from the gas phase ), was first described by Mohammadi et al. [5] and has since been used to produce various conductive polymers in particular polypyrrole. The technique appeared to be promising for producing cell membrane mikromønstring, since it would be enough to make patterning of an oxidizing agent, which could then be used to polymerize EDT from the vapor phase in the same pattern. Figure 3 shows a sketch of the experimental setup. The oxidizing agent b

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