Polylactide Foams with Tunable Mechanical Properties and Wettability using a Star Polymer Architecture and a Mixture of Surfactants

Commercially available low-density, hydrophilic foams are principally produced from nonrenewable petrochemical feedstocks and suffer from challenging disposal avenues and effective recycling. We aim to develop a biodegradable alternative using materials from sustainable chemical feedstocks. Here we report the preparation of expanded poly(lactide) via carbon dioxide-mediated batch foaming under relatively mild conditions (6 MPa CO₂, T ≤ 50 °C). By changing architecture, temperature, and surfactant loading, we obtain tunable densities from 0.05 to 0.3 g/cm³ and compressive strengths from 1.2 to 0.05 MPa. The use of poly(lactide) with a multiarm star architecture is preferable over the linear analogue in preparing low-density foams. Polysorbate and poloxamer type surfactants were incorporated with 4-arm star poly(lactide) enabling further reduction in foam densities and imparting persistent wettability to inherently hydrophobic poly(lactide). The practical utility of these biodegradable poly(lactide) foams was demonstrated as a potential replacement for current phenolic resin-based foams.