In this study, two biodegradable matrices, polycaprolactone (PCL) and polylactide (PLA) were used to encapsulate for the first time a phase changing material (PCM), specifically dodecane (a paraffin which has a transition temperature at -10 degrees C), through the use of the electrospinning technique with the aim of developing coating materials with energy storage capacity for thermal insulation applications. The encapsulation efficiency obtained using both matrices has been studied and the different morphology, thermal properties, and molecular structure of the materials developed were characterized. Results showed that dodecane can be properly encapsulated inside both biopolymers with a submicron drop size, albeit PCL provides better encapsulation performance. A temperature mismatch between melting and crystallization phenomena (the so-called supercooling effect) was observed in the encapsulated paraffin, mainly ascribed to the reduced PCM drop size inside the fibers. Addition of dodecanol was seen to best act as a nucleating agent for the PCL/PCM and PLA/PCM structures, allowing a significant amount of heat storage capacity for these systems without supercooling. These innovative ultrathin structured biomaterials are of interest as energy storage systems to advantageously coat or wrap temperature sensitive products in refrigeration equipment and constitute smart food or medical/pharmaceutical packaging. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3251-3262, 2013