Synthesis of Biodegradable Porous Poly(δ-valerolactone-co-l-lactide) Monoliths from Star-Shaped Poly(l-lactide) Macroinitiators via Eutectic Polymerization

Porous polymeric biodegradable monoliths (PHIPEn, where n denotes the number of arms of the PLA macroinitiator) based on poly(δ-valerolactone-co-l-lactide) were prepared via bulk ring-opening polymerization of a δ-valerolactone/l-lactide (VL/LA) eutectic mixture (80/20) using various PLA macroinitiators. Linear (one- and two-arm) or star-shaped (four- and six-arm) PLA macroinitiators were employed to investigate the effect of initiator functionality on the morphology and properties of PHIPEns. The variation in initiator functionality strongly affected the pore morphology, cross-link density, and overall physical properties of the materials. Increasing the number of arms resulted in smaller pore size, higher cross-link density, greater crystallinity, and improved compressive strength and modulus. Thermal analysis revealed that PHIPEns prepared from star-shaped macroinitiators exhibited improved thermal stability and higher PVL crystallinity compared with those derived from linear macroinitiators. Hydrolytic degradation in phosphate-buffered saline at 37 °C showed that PHIPEns synthesized from star-shaped macroinitiators degraded more slowly, absorbed less water, and maintained a more stable pH than those derived from linear ones. These results demonstrate that combining star-shaped macroinitiators with a VL/LA eutectic mixture provides an effective strategy for designing biodegradable porous materials with tunable properties.