The synthesis of two reactive interfacial agents for starch-polycaprolactone (PCL) blends, PCL-g-glycidyl methacrylate (PCL-g-GMA) and PCL-g-diethyl maleate (PCL-g-DEM) is described. The compounds were prepared by reacting a low molecular weight PCL. (M-w 3000) with GMA or DEM in the presence of benzoylperoxide (BPO) at 130 degrees C. The effect of important process variables (initiator and monomer intakes) on the functionalization degree (FD) of the GMA and DEM units to the PCL backbone was explored in detail and quantified using multivariable linear regression. The highest FD values (up to 45%) were observed for PCL-g-GMA, at relatively high GMA and BPO intakes. The FD values for PCL-g-DEM were considerably lower (up to 7%). The reactive interfacial agents were tested for their performance in starch-PCL blends. The mechanical properties of the compatibilized blends differ from the uncompatibilized ones and in particular the elastic modulus for the compatibilized blends is significantly higher. At relatively low starch intakes, PCL-g-DEM has at least a comparable performance than PCL-g-GMA. These observations may be explained tentatively on the basis of the distribution of the functional groups (GMA or DEM) along the PCL back-bone. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 23152326,2009