Binary blends of poly(lactic acid) and poly(methyl methacrylate) for high energy density and charge/discharge efficiency capacitors

Polymer dielectrics are widely used in modern power electronics due to their high flexibility and high breakdown strength. However, the limited energy density of current polymer dielectrics limits their wider applications, and there is an urgent need to develop novel polymer dielectric materials. Poly(lactic acid) (PLA) is favored for biological applications due to its biocompatibility and biodegradability. In general, PLA has three optical isomers, namely poly(L-lactide) (PLLA), poly(D-lactide) (PDLA), and poly(DL-lactide) (PDLLA), but the investigation of their dielectric properties remains limited. In this study, a significant increase in energy storage density and charge/discharge efficiency in poly(methyl methacrylate) (PMMA) was achieved by incorporating isomers of PLA into PMMA. Experimental results indicate that the introduction of PLA creates a phase-separated structure within PMMA, and in particular, the introduction of the crystalline region significantly improved the breakdown strength (E_b). Finally, PLLA/PMMA 50/50 and PDLA/PMMA 50/50 exhibit the discharged energy densities of 8.55 J cm⁻³ and 8.18 J cm⁻³, respectively, with charge/discharge efficiencies of 89.6% and 90.9%. This work enables the achievement of all-organic dielectrics with high energy storage density and high efficiency through the construction of phase-separated structures and demonstrates the great potential of biodegradable polymers in electronic devices.