Nanotechnology Lect.6

Polymers
A polymer is a large molecule made of a chain of individual basic units called monomers joined together in sequence. A copolymer is a macromolecule containing two or more types of monomers. When the polymer is a good conductor of electricity, it is referred to as conductive polymer (or organic metal). In this lecture, nanostructuring of polymers and the effect this can have on the properties of polymers are described. The focus is on copolymers since these are extremely useful in nanotechnologies.
? Conductive polymers
Polymers that are good conductors of electricity are called conductive polymers and include polyacetylene, polyaniline, polypyrrole, polythiophene — many more have also been synthesised. These polymers are characterised by their alternating double-single chemical bonds, so they are ?-conjugated. The ?-conjugation of the carbon bonds along the oriented polymer chains provides a pathway for the flow of conduction electrons and is thus responsible for the good electrical conduction properties of the material. A detailed SEM analysis of conductive polymers has revealed that these are made of a sequence of metallic nanoparticles about 10 nm in diameter. The high conductivity of polymers such as polyacetylene and polyaniline is related to the nanostructure of the polymer. Polyaniline and its analogues change colour when a suitable voltage is applied, or when reacting with specific chemicals (electrochromic and chemochromic). For this reason, they are promising for use in light-emitting diodes (LEDs). Other applications are the