The radical addition of mercaptans (RSH) onto poly [2-(3-butenyl)-2-oxazoline], which is available through a living/controlled cationic isomerization polymerization, can proceed smoothly in the absence of side reactions, exhibiting the characteristics of a click reaction. The "thio-click" reaction can be performed under feasible ([RSH]/[C=C] similar to 1.2-1.5, no transition metal additives) and mild conditions (generation of radical's with UV light at room temperature) and goes to completion within a day. Hydrophobic fluoropolymers can be prepared in the same way as water-soluble (co-)polymers or glycopolymers, starting from readily available materials.