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Polymers

Introduction of Conductive Polymers Part-2

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Although another conductive polymer, polyaniline, has existed for nearly two centuries, the adventitious discovery of polyacetylene places it at the forefront of conductive polymers, opening up new revolutionary opportunities for experimentation. Although metals are the best available engines today, their use has many disadvantages. Mining, shipping, and metalworking are expensive. Conductive polymers are interesting alternatives because they are light, economical and versatile from a functional point of view. So, how do these conductive polymers work? As with metals, the electric charge flow in conductive polymers is generated by the voltage, a difference in the positive and negative electric potential of a battery or an output. Negatively charged electrons are attracted to the positive pole and generate a current as they pass from one atom to another. But, as already mentioned, the electron of the polymer is normally not delocalized and cannot easily move to conduct the current. But let’s take another look at polyacetylene. If you look closely, you will find that alternating single and double bonds hold the polymer atoms together. This is known as a conjugated main chain.
Along this spine, the sigma bonds hold each atom together by concentrating the electrons directly between them. The Pi bonds, which form the second bond in each double bond, strengthen the bond between their atoms by attracting the electrons above and below the plane and the molecule. This forms delocalized orbitals in which the mobility of electrons can be improved by a process called “doping”. This process essentially changes the number of electrons in the polymer, either by removing or adding electrons to the atoms. The elimination of electrons creates empty spaces in the outermost orbital of the atom, allowing the remaining electrons to move more freely.

The addition of electrons forces one atom to create another orbital, and as long as that orbital is not full, electrons have more room to move and jump from one atom to another. You can think it’s like a pool table full of billiard balls. The balls could move if they did not disturb. But if you remove bullets, the rest can move. Or, if you add more balls, you must add a new pool table. On this new pool table, you have a lot of freedom of movement.

The easier they can move, the easier they can carry loads and conduct electrical currents. Although no one initially believed that polymers could conduct electricity, the scientific community has since stopped researching Shirakawa. In 2000, Shirakawa, MacDiarmid, and Heeger were awarded the Nobel Prize for Chemistry, and research on conductive polymers has grown exponentially, while the potential of conductive polymers has not yet been discovered. There are countless opportunities for technological developments and meanings such as high capacity batteries, artificial muscles, and biosensors. Although we probably do not see plastics completely replacing metals in our lives, the field of conductive polymers has tremendous potential, especially for something that started out as a mistake.

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Polymers

Introduction of Conductive Polymers Part-1

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When you think of electricity, what comes to your mind first? It’s probably a cable. We are used to seeing metals as the best way to conduct electrical energy. And it is true that metals are present in almost every electronic product we use: light bulbs, telephones, computers, televisions and countless other devices. But believe it or not, there are some non-metallic elements, such as conductive plastics, that can also serve as drivers. Their special properties challenge our assumptions about non-metals and enable them to harness the power of electricity. Although electricity may seem magical, the science behind it is pretty simple.

An electric current is just the flow of electrons from one atom to another. Different atoms combine electrons better than others, so materials like metals are more conductive than others. This is because the electrons are delocalized, meaning that the outermost electrons in a metal atom remain loose, allowing them to move more freely. On the other hand, the outer electrons in the non-metallic atoms are held closer to the core, preventing movement. Think of the electrical cable. Inside, the charges flow easily through the metal threads. On the outside, the gum prevents these charges from circulating in our bodies and kills us when we touch the cord. But electrically conductive plastics turn this idea into a head. These plastics are polymers, long chains of smaller repeating units known as monomers. By changing the structure of the atoms in the monomers, these plastics can become as conductive as some metals. Sounds good, right?

You may think that a brilliant chemist made this plastic specifically for this purpose. But like many other important discoveries in science, it was an accident. This happened in Hideki Shirakawa’s laboratory when the chemical polyacetylene compound was poorly mixed. Usually black and dusty, the compound instead formed a silver film that looked distinctly metallic. Wondering whether this strange substance would have metallic properties, Shirakawa shared the discovery with chemist Alan MacDiarmid and physicist Alan Heeger. After experimenting with many different processes, they discovered that they can increase the conductivity of polyacetylene to compete with certain metals. For example, with the addition of brominated gas, the conductivity of polyacetylene has increased 10 million times to a level close to that of copper.

 

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