New polymer materials, including thin films, soft gels, and hollow capsules, consisting of composite polymer nanofilms were prepared by the Cu(I)-catalyzed Huisgen click reaction between lipophilic polymers or between lipophilic and hydrophilic polymers. Because the lipophilic polymer, or hydrophilic polymer and copper catalyst were present in the oil or aqueous phase, respectively, the crosslinking reaction proceeded only at the phase interface. The combination of lipophilic and hydrophilic polymers produced "Janus" nanofilms with both hydrophilic and lipophilic surfaces.