Interfacial polymerization is a polymerization technique in which the polymer forms at the interface between two immiscible solvents. It is used primarily for the preparation of high-molecular-weight polymers such as nylon 66. Nylon 66 is made by reacting hexamethylenediamine with adipoyl chloride, forming a polymer at the interface of the two phases.
Nylon 6, on the other hand, is made through ring-opening polymerization, not interfacial polymerization.
Thus, the correct answer is Nylon 66.