Question

need help on polymer chemistry question

Determine which polymerization mechanism(s), i.e. radical, anionic, and cationic, can be used for the following monomers. Briefly explain your answer.

H2C=CHCI HỌC =CHCN H2C= C(CN)

Answer 1

Anionic polymerization mechanism for all the three monomers.

In anionic polymerization, the propagating chain is a carbanion. In this case, the initiator is an anion (an ion with a negative charge). The monomers having substituent groups which are capable of stabilizing to the carbanion through inductive effect or resonance are highly susceptible to anionic polymerization.

1. The substituent group present in the first monomer H₂C = CHCl is chloro group which stabilize the carbanion by -ve inductive effect.

2. The substituent group present in the second monomer H₂C = CHCN is cyano group which stabilize the carbanion by -ve inductive effect.

3. The substituent groups present in the second monomer H₂C = C(CN)₂ are the two cyano groups which stabilize the carbanion by -ve inductive effect.

Inductive effect which stabilises to the carbanion will be highest in H₂C = C(CN)₂ and lowest in H₂C = CHCl among the three given monomers.