Question

Radical copolymerization of MMA 1.000 g and styrene 1.000 g occured in toluene solution(18 mL) and initiator is AIBN(0.020 g)

Solution was purged with N2 gas.

What was happened if PDI of this solution is 1.11?

Theoritical PDI of this reaction is 1.5 to 2.0(disproportionation = 2.0, coupling reaction = 1.5)

Answer 1

The mass of MMA = 1 g

The molar mass of MMA = 86 g/mol

Therefore, the no. of moles of MMA = 1/86 = 0.0116 mol

The mass of styrene = 1 g

The molar mass of styrene = 104 g/mol

Therefore, the no. of moles of styrene = 1/104 = 0.0096 mol

The mass of AIBN = 0.02 g

The molar mass of AIBN = 164 g/mol

Therefore, the no. of moles of AIBN = 0.02/164 =0.0001 mol

The observe PDI of the solution = 1.11

Theoretical PDI of the reaction = 1.5 (coupling reaction)

= 2.0 (disproportionation)

Explanation: The observed PDI (1.11) of the solution is less than that of the theoretical PDI (1.5 to 2).

Most probably, there happened an alternating copolymerization between MMA and styrene, having almost the same units of MMA as well as styrene, resulting in the PDI ~ 1 (1.11).