Polymer

The term "Polymer" refers to a macromolecule composed of several molecules, which can be of one (or even more) types of atoms (or directly groups of atoms). It is true that many of the chemical and physical properties do not change when we remove or add one (or more) similar constitutional units.

Modern polymers are usually formed today with the help of a process known as polycondensation or polymerization.

The key thing that distinguishes other materials from polymers is the so-called chain-structured arrangement of all the molecules within them - these are typically long linear structures of interconnected atoms (or their groups), where a certain regular structure is evident. This regularity can (but does not have to) be interrupted in places due to branching (then it is a so-called graft polymer, or branched polymer, or even so-called polymer networks).

This information is crucial because otherwise we could even consider diamonds as polymers (or today's popular graphene), since their molecular weights are similarly high.

To have complete information – it was not long ago when the term polymer only referred to macromolecular substances formed from molecules with the formula Xn " (where number n indicated how many times the structure repeats). However, we must not forget that today the term polymer also refers to substances that are explicitly non-chemical in origin: such as nucleic acids and various proteins. This is, of course, because their molecular structure consists of a gigantic number of very similar structural items that are constantly repeating.

In order for the field of modern chemistry and polymers to be more comprehensible, fortunately, scientists have decided to clearly distinguish things: for example, all polymers formed from biological origin today fall under the term biopolymers (or biomacromolecular substances). For example, perhaps the best-known biopolymer is cellulose, which contains around a thousand units of glucose. This is also why cellulose has such a high relative molecular weight (around 200,000).

Examples of common chemical polymers in practice

Perhaps the most well-known representative of common chemical polymers is polyethylene, which can be represented as:

H―(CH2)n―H

or:

H―(CH2―CH2)n―H

when one wants to emphasize that it was formed through the polymerization of ethene/ethylene.

Another relatively well-known polymer is so-called polybutadiene (the oldest synthetic rubber):

H―(CH2―CH═CH―CH2)n―H

we can also have polybutadiene terminated with a hydroxyl group (HTPB), which then looks like this:

HO―(CH2―CH═CH―CH2)n―OH

Another good example of a modern (and no longer entirely simple) polymer is polyvinyl chloride (PVC):

H―(CH2―CHCl)n―H

What structures can polymers have?

All of the above-mentioned polymers are unbranched and straight structures. However, if we want to familiarize ourselves with a more complex polymer, a good representative is the well-known natural rubber for everyone. Natural rubber is derived from the monomer unit of isoprene hydrocarbon (or synthetic provenance polystyrene can also serve).

Polymers of all types, of course, do not have to create just simple and linear substances. Even among the connections of monomer units, chemical bonds can arise - which then form the specific and unmistakable spatial/planar structure of the given polymer.

All polymers can also be formed from more than one monomer, thus they are referred to as copolymers. The molecules here may or may not have a regular structure of their monomer units. From this, it logically follows that both nucleic acids and proteins are, from this perspective, obvious copolymers.

What are the mechanical properties of polymers?

Unquestionably, the most important factor that interests humanity about all chemical polymers is their mechanical and physical properties. These precisely determine how the given polymer will behave in the macroworld and on a larger scale.

• Tensile strength – this property of the given material (and polymers are no exception) determines how much elongation the polymer can withstand before it breaks. This is a very important aspect because it is usually the most crucial factor for them. Generally speaking, the tensile strength of a given polymer increases with the length of its chain/creating a more complex network-type structure, as in the case of cellulose.
• Elastic modulus – indicates how elastic a specific polymer is. It is defined for fibers of a certain length and thickness. This value is furthermore not fixed and changes considerably with temperature.