Synthesis of core cross-linked star (CCS) polymers via a two-step one-pot process involving the synthesis of living near arms followed by a cross-linking step to generate CCS polymers, is discussed. Ring-opening polymerization (ROP) of a lactone was performed in the presence of a catalyst and an initiator in toluene to produce living linear polycaprolactone (PCL) arms. It was followed by addition of a bislactone, which acts a cross-linking component under ROP conditions to give the core structure. This bislactone was used as the cross-linking agent due to its structural similarity with the lactone such that the core of the star polymer would chemically resemble PCL only with bridges linking between the pentylene moieties. The conversion of the bislactone monomer during the second stage of the reaction was monitored by gas chromatography mass spectrometry, which showed that after 16 h 86% of the monomer had been consumed.