A self-assembled monolayer on a planar gold substrate has been used to initiate the living cationic ring-opening polymerization of 2-ethyl-2-oxazoline. The polymer chain end was functionalized with an alkyl moiety by means of the termination reaction in order to form an amphiphilic brush-type layer. The resulting layer (d similar to 10 nm) of linear poly(N-propionylethylenimine) (PPEI) is of uniform thickness and was found to be very stable.