Addition and Condensation Polymerization

Addition polymers: They are formed by the addition of olifinic monomers without the elimination of byproducts.  Polymerization is brought about by linking together simple unsaturated molecules such as alkenes (ethylene and propylene) or substituted alkenes (vinyl; CH₂=CH₂-group).  Examples: polythene, polypropylene, PVC, Plexiglas, etc.

Polyethylene is made by the addition polymerization of ethylene. Addition Polymerization is initiated using small amounts of substances called initiators. Water soluble potassium persulphate and dibenzoyl peroxide which is soluble in organic solvents have been used as initiators. The introduction of Ziegler catalysts as initiators has made possible the synthesis of polymers which had earlier been found to be either difficult or impossible. One of the Ziegler –Natta catalysts is a combination of titanium tetra chloride and triethyl aluminium. A characteristic feature of the catalyst is that it imparts a regular structure to the polymer.

What is Polymerization

Polymer and Polymerization

A polymer is a giant molecule of high molecular weight obtained by the repeated union of a large number of simple molecules (monomers). Polymers are also called macro molecules. The monomer molecules are linked together through covalent linkages. The properties of a polymer are entirely different from those of the monomer.

Monomers (Greek, monos = one, mers = units or part):  These are repeating simple molecules having two or more bonding  sites through which each can link to other monomers to form a polymer chain. Monomers are often called building blocks of a polymer chain. The total number of functional groups or bonding sites present in a monomer molecule is called the functionality of the monomer. For a substance to act as a monomer, it must have at least two reactive sites or bonding sites

Polymerization: A chemical process of obtaining a polymer from its monomers is called polymerization.