Question

Which of the following polymers can be made by cationic addition polymerisation mechanism?
A.PVC
B.PP
C.HDPE
D.LDPE

Answer 1

Cationic addition polymerisation is applicable to vinyl monomers containing ${e^ - }$ releasing groups. PP (polypropylene) polymerizes by the cationic polymerization reaction. It is made from the polymerization of propene monomers (an unsaturated organic compound).

Complete step by step answer:
When the initiator is cationic in nature (such as from the acid), in addition to the double bond, it would generate a cationic intermediate for carrying the addition chain process is called cationic intermediate for propagating the addition chain process which is called cationic addition polymerization. In this case, the cationic polymerization reaction is initiated by adding a strong acid to an alkene to form a carbocation. Cationic addition polymerisation is applicable to vinyl monomers containing ${e^ - }$ releasing groups.
PP (polypropylene) polymerizes by the cationic polymerization reaction. It is made from the polymerization of propene monomers (an unsaturated organic compound).
HDPE (high density polyethene) and LDPE (low density polyethene) polymerize by Ziegler-Natta Catalytic polymerization reaction. Ziegler-Natta catalysts produce a more linear polymer that is more rigid and has a higher density and a higher tensile strength. The rapid polymerization occurs at atmospheric pressure and moderate to low temperature which gives a stronger and more crystalline product (HDPE) than that from radical polymerization (LDPE).
PVC (Poly vinyl chloride) is made by free radical polymerization in suspension. Here, the initiator of the reaction is a free radical. During polymerization, the polymer precipitates out as it is formed, since it is insoluble in the monomer.

Therefore, the correct answer is option (B).

Note: Addition polymerisation is the process to create massive molecules from monomers with double bonds under the high temperature and high pressure.
Under high temperature and pressure, compounds with $C = C$ double bonds (usually $s{p^2}$ hybridised with at least one pure pi orbital) can undergo additional polymerisation. There is a side on overlap of the π orbitals in addition to the stronger σ bond. Under the correct conditions, the pi bond is broken and the carbons become $s{p^3}$ hybridised to form another σ bond with other monomers.