2. Crystalline polymers

Not all polymers lend themselves to crystallization: only chains characterized by a regular, symmetrical conformational structure, or those carrying groups capable of strong molecular interactions (hydrogen bonds), are likely to form crystalline zones. Macromolecular chains assemble in these crystalline areas according to the principle of minimum congestion and the most energetically stable state.

The crystallization process actually involves three levels of organization:

• the crystal lattice, reflecting the conformation of the chain and its position in relation to neighbouring chains;

• the crystalline lamella, corresponding to the higher state of association, formed by accordion-like folded chains; the thickness of these lamellae is of the order of 10 to 20 nm. On the other hand, in...