Question

Explain why polyacetylene is an electrical conductor whereas polyethylene.

Answer 1

there are certain factors involved which decides weather the polymer is gone be conducting or not. Here in the case of the Polyacetylene ( IUPAC name Polyethyne) and polyethylene the concept of the sp3 and sp2 and valence elctron plays most important part and are responsible for conducting behavior.. For example, in thermoplastic polymers such as polyethylenes, the valence electrons that are present in the outershell are more stable oriented in sp3 hybridized covalent bonds. which consist of "sigma-bonding electrons" because of this valence elctrons have low mobility and which in turn do not contribute to the electrical conductivity of the material. However, in some of the other materials, the situation is althoghther different.

The polymers which have ability to conduct electricty have backbones of contiguous sp2 hybridization carbon centers. One valence electron on each carbon center lies in a pz orbital, which is perfectly perpendicular to the other three sigma-bonds. All the pz orbitals of the all differnt shell combine with each other to a molecule wide delocalized set of orbitals. The electrons in these decetralized orbitals have high mobility when the material is "doped( mixed with any other material whichh have ant kind of special property)" by oxidation, which removes some of these decentralized electrons.

Thus, theconjugated p-orbitals form a one-dimensional electronic band, and the electrons that are present in this band become more mobile when it is partially emptied.

In principle, these same materials can be doped by reduction, which adds electrons to an partially filled band.

And hence this kind of hybridized orbital are responsible for this behavior. Doping is usually done to increase the conducting potential of a material to use it for commercial purpose.

In practice, most organic conductors are doped oxidatively to give p-type materials. The redox doping of organic conductors is analogous to the doping of silicon semiconductors.