Many molecules connect to each other, where lots of water molecules are formed as a side product (or sometimes another small molecule)
A macro molecule is produced via a condensation mechanism.
Glycol C2H4(OH)2, with two OH-groups per molecule, can suffer a polycondensation process in two directions.

HO – CH2 – CH2 – OH

Each OH-group can react with the OH-group of another molecule. Every time water is formed.
The glycol molecule can extent to two sides.

The product is, in this case, a polyether, a solid, while the reactant glycol is a liquid.

Famous polycondensation products are:
  1. Polyethers
  2. Polyesters
  3. Polypeptídes
  4. Polysaccharides

Copolymerisation is the process where participate more than one kind of monomers.
In the industry many copolymeres are invented, made and applied.
For example, the material of videotapes are a copolymere product of the two monomeres: glycol (1,2-dihidroxyethane) and tereftalic acid (1.4-dicarboxylbenzene ).

Question 24
Copolymerisation of the monomeres glycol and oxalic acid is possible, with a little bit of concentrated sulfuric acid as a catalyst.
This reaction starts with an attack of protons at oxalic acid, whereby a carbonium ion is formed (a C with a positive charge). This is the slow step of the reaction. The slowest step determines the total reaction rate.