Question

Answer the following in 1-3 sentences each.

a) Summarize the causes and effects of the Tromsdorff (or autoacceleration) effect in chain polymerization.

b) In a free radical polymerization of polystyrene, how can [I] and [M] be changed such that Rp is the same but DPn is reduced by a factor of 2?

c) Why can’t free radical polymerization (in general) be used to make block copolymers?

d) What is [M] (in mol/L) for a bulk PS polymerization?

Answer 1

a) Tromsdorff or autoacceleration effect in chain polymerisation occur due to increase in localized viscosity of the polymeric system under study as a result of which there is a rapid increase in overall rate of the reaction and alters the properties of the resulting polymer.

b) Degree of polymerisation can be given as:

If DPn' = DPn/2 and Kp'= Kp then

c) Due to the presence of inherent termination reactions involving chain transfer & disproportionation reactions, there is lack of control of molecular weights resulting in inability to obtain complex macromolecular structures such as block polymers.

d) For bulk PS polymerisation, [M] is the concentration of monomer units present in the bulk