Size Exclusion Chromatography (SEC). The number-average and weight-average molar masses (Mn and Mw) and the molar mass distribution (Ð) of the tetra-PCL-based star polymers 3a-c, 5b and 5c presented in Table were determined using an isocratic HPLC pump (Agilent 1200) with autosampler (Agilent Technologies, Santa Clara, CA) equipped with twofold detection (SEC-MALS/dRI). Details are described in the SI Chapter 5.