Question

Q3 (25 pts) The polymerization is done by the anionic mechanism, and 2 mol of polystyrene is polymerized in tetrahydrofuran (THF). Polymerization was initiated by 1.5 x 10-3 mol of sec- Buli. a) What is the expected number average chain length? (5 pts) b) What is the expected number average chain length if the efficiency of the initiator is 80%? (10 pts) c) At 75% conversion, 0.5 x 10-3 mol of water is added and the reaction continues. What is the number average molar mass at the full conversion? (10 pts) Q4 (20 pts) List main advantages (10 pts) and disadvantages (10 pts) of the anionic polymerization

Answer 1

The advantages and disadvantages of the Anionic Polymerisation are as shown below:

Advantages:

1)There is a requirement of less activation energy for the initiation of anionic polymerisation reactions.

2)The distribution of molecular species will be of narrower range.

3)The chain reactions will be of limited number.

4)Polymer molecules of regular size are eaily produced from this type of mechanism.

5)The reaction are carried out at lower temperatures and also the formed polymers can have low branches in the structures.

6)The groups which are at the end of the polymer chain can be further participate in the reactions.

Disadvantages:

1)The reactions are slower in nature.

2)Difficult to maintain these reactions at industrial scales as there will be no termination in the reactions as the groups which are at the end of the polymer chain can be further participate in the reactions.

3)Sensitive for the solvents,as the chain structures formed can be transfered into the solvent.