Question

31. What is the initiator in the polymerization of isobutylene? 


32. What is the general name of the product produced by cationic initiation? 


33. What reactant besides the monomer is present in cationic chain propagation reactions? 


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Answer 1

Solution 31:: Acid-forming systems such as boron trifluoride with traces of water react with a monomer to produce a cationic intermediate. Such initiation is used in the polymerization of isobutylene.

Basically, cationic polymerization just needs cationic intermediates which can be easily obtained using acidic reagents.

Example:

Solution 32: As the name suggests, the general name of the product produced by cationic initiation must be kind of "cationic".

So, during initiation, a "carbenium ion" is generated from which the polymer chain is made. It is electrophillic in nature.

Solution 33: Propagation proceeds by addition of monomer to the active species, i.e. the carbenium ion. The monomer is added to the growing chain in a head-to-tail fashion. In the process, the cationic end group is regenerated to allow for the next round of monomer addition.

General reaction::