To obtain a set of polycaprolactones (PCL) with varying crystallinity, the triazabicyclodecene-catalyzed co-polymerization of the two constitutional isomers epsilon-caprolactone (epsilon CL) and delta-caprolactone (delta CL) was carried out at room temperature in toluene. Variation of the feed fraction of epsilon CL from 50% to 80% and the detailed kinetic studies accompanied by application of terminal as well as nonterminal kinetic models suggested the formation of random copolymers. Differential scanning calorimetry and wideangle X-ray scattering investigations revealed the decrease of melting temperatures and degree of crystallinity with the epsilon CL fraction in the PCL. All copolymers were suited to obtain aqueous nanoparticle dispersions by means of nanoprecipitation. Encapsulation of the fluorescent probe pyrene confirmed a constant hydrophilic/hydrophobic balance of the nanoparticles.