Green Polylactide/Cellulose Nanocrystal Nanocomposite Foams with Superior Compressive and Thermal Insulation Properties via Interfacial Stereocomplexation

Incorporating nanoparticles is a common strategy to enhance the cellular structure and mechanical properties of poly(lactic acid) (PLA) foams. However, conventional nanoparticles often compromise the intrinsic green nature of PLA and suffer from poor dispersion and weak interfacial adhesion, limiting their effectiveness in the development of high-performance green foams. Herein, a sustainable approach was presented by grafting poly(D-lactide) (PDLA) onto biodegradable cellulose nanocrystals (CNCs), which were subsequently incorporated into the poly(L-lactide) (PLLA) matrix. The interfacial stereocomplexation between the two enantiomers not only improves CNC dispersion but also strengthens interfacial interactions. Consequently, PLA composite foam with a high expansion ratio (up to 48.5) and a fine bimodal cellular structure was fabricated via an eco-friendly supercritical CO₂ foaming process. The resulting foams exhibit superior thermal insulation (thermal conductivity as low as 31.7 mW/(m K)) and a specific compressive modulus 213% higher than that of neat PLLA foam, highlighting their potential for sustainable packaging and construction applications.