What the term polymer mean? One thus indicates a system formed by a collection of macromolecules, i.e. molecular species of large size, called macromolecules, resulting from the covalent bond between repetitive units called monomers. These macromolecular species thus defined have sizes (characterized by their molar mass) much higher than those of the simple molecules. As a result macromolecular nature, new properties are observed for the corresponding systems, properties usable, in particular, in the field of structural materials.

Polymers possess molar masses ranging between a few thousand to several million of g/mole. In the case of the three-dimensional polymers, the molar mass can be regarded as infinite.

Remarks

a) The terms “polymer” and “macromolecule” are often confused. Certain specialists preferentially reserve the term “macromolecule” to those of biological origin, being often more complex in their molecular structure, than that of synthetic polymers. For our part, we will use the two terms interchangeably.

b) The terms “monomer” and “polymer” are, at the same time, adjectives and gerunds.

The number of monomeric units which constitute a polymeric chain is called the degree of polymerization (DP); it is directly proportional to the molar mass of polymer. The assembly, within a macromolecular chain, of a small number of monomeric units, is called sequence and the first terms of the series of the sequences are indicated by diad, triad, tetrad, pentad, etc. The chains made up of a small number of monomeric units are called oligomers; typically, the degrees of polymerization of oligomers vary from 2 to 20.

Reactions of polymerization transform called simple monomeric molecules (or monomers) into a whole polymer resulting from the covalent assembly of unit monomers. When several monomers (indicated by comonomères) are used simultaneously to form polymer, the result is called a copolymer.

The covalent assembly of the monomeric units can utilize a variable number of connections; the number of connections which associated with the covalent assembly of the repetitive units (monomeric units) is called valence, preferable to the term functionality which can lead to confusion. The monomeric units can thus be mono, di-, tri- or tetravalent and the monomeric molecules from which they result are they also qualified mono, di-, sorting or tetravalent. The average valence of the monomeric units of a macromolecular system determines its dimensionality, i.e. the way in which the monomeric units in space are laid out.