Factors Favoring Catenation

The tendency of atoms of certain elements to form chains with themselves (homoatomic catenation) or in alternation with other atoms (heteroatomic catenation) is of extreme importance in chemistry. The immense subject of organic chemistry and, indeed, life as we know it depend on the special ability of carbon to catenate from the chemical engineering standpoint, catenation and the associated ability to form molecular rings and cages provide opportunities to make materials of desired mechanical, electrical, thermal, chemical, or catalytic properties. 

Condensation polymerization, in which some very stable molecule XZ is eliminated from equimolar amounts of species R E—X and Ra,E—Z (E being the element that catenates and R some side group), is more widely applicable  

The success of reaction 3.2 in producing long-chain polymers depends on having precisely equimolar amounts of the two pure reactants, and essentially complete reaction otherwise, small polymeric molecules oligomers) will be produced instead. Accordingly, a rather more effective variant of reaction 3.2 has X and Z in the same molecule  

---