Question

Polymer Chemistry:

1. (20pt) This question is concerned with a comparison between step and chain polymerization. A. Indicate which of these statements is appropriate to step and which to chain processes: a. High MW obtained initially and continuously. b. High MW at high conversion. 2. a. Monomer concentration decreases rapidly in early stages of reaction. b. Monomer concentration decreases continuously throughout reaction. 3. a. Reaction mixture contains only high polymer, monomer and reactive species. b. Reaction mixture contains a range of different sized species. B. Discuss the reasons for your choice in any one of the sections in part A in terms of the mechanisms of step and chain polymerization.

Answer 1

In step growth polymerisation reaction two monomer combine together to form a diamer then these diamer combine to form trimer and tetramer and similarly reaction proceed , so molecular weight of the polymer formed is high at higher conversion.

In chain growth polymerisation after initian , there is unchecked growth in the polymer chain so high molecular weight polymer are formed at low conversion,

1 a) This statement is true for chain growth polymerisation.

b) This statement is true for step growth polymerisation.

2) In step growth polymerisation since monomer reacts with each other to form diamer , monomer concentration decreases rapidly at the early stage of the reaction.

So statement a is correct for step growth polymerisation.

b) Chain growth polymerisation starts when an initiator adds to a monomer and then keeps on adding with the other monomers, monomer concentration decreases continuously throughout the reaction.

So this statement is true for Chain growth polymerisation.

3 In chain growth polymerisation once the initiator starts the reaction monomers keeps adding to the polymer chain formed and hence in reaction mixture we can find high polymer, monomer and reactve species.

So statement a is true for chain growth polymerisation.

In step growth polymerisation, two monomer adds up to form diamer, now diamer adds with another diamer to form a tetramer or with a monomer to form trimer , similarly two tetramer can add up to form an octamer or a tetramer and add up with a trimer or monomer to form septamer or pentamer respectively, Hence reaction mixture contains a range of different sized species.

So statement b is true for step growth polymerisation.

Please uovote

Thank you!