Impact of modulating the molecular weight on the structural features and final properties of PLA aerogels

Achieving precise control over structural parameters is crucial for optimizing the performance of bio-based aerogels in energy-related applications. In this work, we investigate the influence of molecular weight and concentration on the development of sustainable polylactic acid (PLA)-based aerogels tailored for thermal insulation. The effects on density, porosity, crystallinity, morphology of the porous structure, mechanical strength, and thermal conductivity were systematically analyzed. It was observed that higher molecular weight PLA can reduce shrinkage during the drying step, leading to lighter aerogels. The relationship between chain mobility (governed by the solution viscosity) and molecular weight was found to be key in governing the microstructure morphology. Sound speed measurements revealed significant variations in the structural factor (g), which are intrinsically associated with the material’s solid tortuosity, and thus in the mechanical and thermal properties. The elastic modulus and compressive strength increased by up to 170 % and 63 % in samples with densities of ca. 100 kg/m 3 and 140 kg/m 3 , respectively, when the molecular weight was increased from 138 to 175 kDa. Furthermore, all aerogels maintained low thermal conductivities (∼30 mW/m·K), and some of them showed values clearly below 30 mW/m·K, owing to a reduction in various heat transfer mechanisms resulting from modifications in key structural parameters, such as porosity and pore size. These findings provide a scalable strategy to engineer bio-based, low-density, and mechanically robust PLA aerogels with stable thermal properties, advancing their deployment as sustainable alternatives to fossil-based insulation materials in clean energy and environmental technologies.