Nanocomposite Materials with Poly(l-lactic Acid) and Transition-Metal Dichalcogenide Nanosheets 2D-TMDCs WS₂

Layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS₂) were introduced via melt processing into poly(l-lactic acid) (PLLA) to generate PLLA/2D-WS₂ nanocomposite materials. The effects of the 2D-WS₂ on the morphology, crystallization, and biodegradation behavior of PLLA were investigated. In particular, the non-isothermal melt-crystallization of neat PLLA and PLLA/2D-WS₂ nanocomposites were analyzed in detail by varying both the cooling rate and 2D-WS₂ loading. The kinetic parameters of PLLA chain crystallization are successfully described using the Liu model. It was found that the PLLA crystallization rate was reduced with 2D-WS₂ incorporation, while the crystallization mechanism and crystal structure of PLLA remained unchanged in spite of nanoparticle loading. This was due to the PLLA chains not being able to easily adsorb on the WS₂ nanosheets, hindering crystal growth. In addition, from surface morphology analysis, it was observed that the addition of 2D-WS₂ facilitated the enzymatic degradation of poorly biodegradable PLLA using a promising strain of actinobacteria, Lentzea waywayandensis. The identification of more suitable enzymes to break down PLLA nanocomposites will open up new avenues of investigation and development, and it will also lead to more environmentally friendly, safer, and economic routes for bioplastic waste management.