What are polymers?
Polymers are called a set of usually organic macromolecules, which result from the union of simpler molecules called monomers by chemical covalent bonds. This is how long molecular structures are joined together by different forces (hydrogen bridges, Van deer Waals forces or hydrophobic interactions). The polymers from polymer manufacturing can be of natural or synthetic origin and process called polymerization. In which phenomena such as temperature, reaction time or the nature of the monomers will determine the length of the resulting chain.
The word polymers comes from the union of two Greek words: ploys (“many”) and mere (“parts, segments”), and were named for the first time in 1866 by Marceline Berthelot. Many of the materials used by mankind since ancient times are polymers, such as wood, wool or silk, and from its modification. It was possible to obtain more resistant and useful forms of them, before even understanding much about their molecular complexity. The first fully synthetic polymer was obtained in 1907, when Dutchman Leo Hendrix Baekeland developed Bakelite, from phenol and formaldehyde.
Beyond the IUPAC standards established to name chemical substances, polymers are usually named by taking the name of the base monomer for their conformation, preceded by the prefix poly (“many”). Thus, we talk about polystyrene, polyethylene, etc. Another common way is to add the word “rubber”, “rubber” or “acrylic” before the name of the copolymers, such as styrene-butadiene rubber, or phenol-formaldehyde resin. Finally, there are some polymers with their own names, usually derived from the brands that sold them, such as nylon (polyamide), Teflon (polytetraflurethylene) or neoprene (polychloroprene).
Polymers are usually classified according to their origin, in:
- Those of natural origin, from nature, such as amino acids or proteins.
- Semi-synthetic. They are obtained from the transformation of natural polymers.
- Obtained industrially by handling organic monomers.
- Those whose chain of molecules is primarily composed of carbon (C).
- Vinyl organic. They have mostly carbon atoms, but combined with other halogen, styrene or olefin formations.
- Organic non-vinyl. They have oxygen (O) and nitrogen (N) in addition to carbon atoms.
- They can be based on sulfur (S) or silicon (Si).
Structure of polymer
- Chemical characteristics of polymers
They are often bad conductors of electricity, so they are often used as insulators. It is also frequent that they have electrochromism (change of color before electricity) and in some cases phosphorescence or fluorescence. Synthetic polymers are poorly reactive, although the presence of organic acids and solvents usually corrodes quickly.
- Physical characteristics of polymers
Polymers are usually crystalline, in cases of more orderly structures, although their presentation can be very varied. They respond to low temperatures by acquiring more hardness and vitreous properties. While at higher temperatures they are more elastic until they reach their melting temperature (Tuf) at which their crystalline cells merge. Much higher is the decomposition temperature, at which the bonds between the monomers dissolve.
The polymer construction process is polymerization, and consists in the covalent bonding of the different monomers that comprise it. This process can be of two types:
By condensation. It results in copolymers and homopolymers, through the loss of a small molecule (of water, for example) in each monomer bond. It is also known as stage polymerization.
By addition. It occurs in a three-phase process: initiation, propagation and termination, during which a hemolytic rupture occurs and the monomers come together.
Polymers are hugely versatile. Their resistance to electric conduction has made them ideal for coatings and insulators, as well as some of very high melting point also serve to insulate cookware. In other cases, suitable building materials result, for coatings and waterproofing, or as structural material.