A new route to poly(e-caprolactone) (PCL) conjugates is described. It is based on successive reactions: the formation of a polycarboxylated PCL via an anionic carboxylation of PCL, the activation of the carboxylic acid group via an acyl chloride group, the conversion of the acyl chloride group to an azide group and finally the formation of an isocyanate group by the Curtius rearrangement. The various steps were monitored using FTIR spectroscopy. To exemplify the potential of the method, isocyanated poly(e-caprolactone) was reacted with UV-absorbing, model, alcohol- and amine-bearing small molecules that were bound to the PCL skeleton via carbamate or urea bonds, respectively. FTIR spectroscopy, SEC with refractometric/photodiode-array double detection, and 1H NMR spectroscopy were used to assess the effective binding of the drug models on the polymeric backbone. The thermal transitions of the conjugates were characterized using DSC.