Q.Classify the following polymers as addition or condensation.
i. PVC ii. Polyamides iii. Polystyrene iv. Polycarbonates v. Novolac

Polymerization converts small, reactive monomers into a single high molecular mass polymer joined by covalent bonds, through one of three distinct mechanisms. Addition (chain-growth) polymerization simply adds monomer units, one after another, to a growing chain without losing any small molecule, so the repeating unit keeps exactly the same elemental composition as the monomer; it happens with monomers carrying a C=C double bond (also called vinyl polymerization) and most often proceeds by a free-radical chain mechanism in three steps -- chain initiation (an initiator such as benzoyl or acetyl peroxide decomposes to generate a free radical), chain propagation (that radical adds rapidly to one monomer after another, building a large radical), and chain termination (most commonly, two growing radical chains combine, ending chain growth). Condensation (step-growth) polymerization instead builds the chain through a series of condensation reactions between polyfunctional monomers, each step eliminating a small molecule such as water, HCl, methanol or ammonia, so the repeating unit's elemental composition differs from that of the starting monomers -- terylene, formed from ethylene glycol and terephthalic acid with loss of water, is the standard example. Ring-opening polymerization is the third mode: a cyclic monomer (a lactam, cyclic ether or lactone), catalyzed by a strong acid or base, has its ring opened and adds on one unit at a time to the growing chain -- nylon 6 from epsilon-caprolactam is the standard example; its repeating unit keeps the monomer's elemental composition (like addition polymerization) but it adds single units in sequence, so it behaves like a step-growth process similar to condensation polymerization.