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Polylactic Acid (PLA) thin films have emerged as an eco-friendly alternative for nonbiodegradable polymers in industrial coatings. As such, our investigation characterized the interfacial diffusion and crystal formation in thin films (PLA, polystyrene (PS), and deuterated styrene methyl methacrylate (dSMMA) blends) on different substrates. AFM data showed that larger molecular weight PS additives increased crystal size and roughness of PLA-PS annealed samples. In bilayer samples, we found a 32% roughness decrease in PS/dSMMA on PLA compared to PLA on PS/dSMMA samples. SIMS data showed that dSMMA was nearly absent in the PS layer and interfacial thickness increased with dSMMA concentration. Previous studies proved dSMMA’s compatibilizing property in bulk[1]; we prove dSMMA retains this property under confinement without compromising crystallinity. This study shows that substrates influence the roughness and crystallinity of PLA thin films and that dSMMA is an effective compatibilizer of PLA and PS thin films which is a promising sign for future use in bioelectronics.
[1] Guo, Yichen, et al. “Enhancing Impact Resistance of Polymer Blends via Self-Assembled Nanoscale Interfacial Structures,” Macromolecules, 2018.