<p>Polycaprolactone-co-polyethylene glycol (PCL/PEG) is a biodegradable and biocompatible copolymer that combines the hydrophobicity of polycaprolactone (PCL) with the hydrophilicity of polyethylene glycol (PEG). This combination yields amphiphilic copolymers with tunable mechanical, thermal, and degradation properties, making them highly valuable across biomedical and industrial applications. In this work, PCL and PEG-based copolymers were synthesized via ring-opening polymerization (ROP) of ε-caprolactone (ε-CL), following an eco-friendly, solvent-free approach using a reusable, easily removable solid-state tin-based catalyst. Key synthesis parameters, including reaction temperature and time, PCL/PEG ratio, PEG molecular weight, and catalyst content, were varied. A Quality by Design (QbD) framework was applied to identify Critical Process Parameters (CPPs) based on their effect on molecular weight, dispersity, and conversion. To further assess process risk and prioritize control strategies, Failure Mode and Effects Analysis (FMEA) was integrated into the QbD methodology. The analysis identified the PEG/PCL ratio as the most critical parameter due to its strong influence on hydrophilicity and molecular architecture.</p>