Abstract
Novel multifunctional biopolymer blend nanocomposites composed of poly(vinylidene fluoride)(PVDF) and tungsten disulfide nanotubes (INT-WS2) that are layered transition metal dichalcogenides (TMDCs) were easily prepared by applying an economical, scalable, and versatile melt processing route. Furthermore, their synergistic effect to enhance the properties of poly(L-lactic acid) (PLLA) matrix was investigated. From morphological analysis, it was shown that the incorporation of 1D (INT)-WS2 into the immiscible PLLA/PVDF mixtures (weight ratios: 80/20, 60/40, 40/60, and 20/80) led to an improvement in the dispersibility of the PVDF phase, a reduction in its average domain size, and consequently a larger interfacial area. In addition, the nanoparticles INT-WS2 can act as effective nucleating agents and reinforcing fillers in PLLA/PVDF blends, and as such, greatly improve their thermal and dynamic-mechanical properties. The improvements are more pronounced in the ternary blend nanocomposites with the lowest PVDF content, likely due to a synergistic effect of both highly crystalline PVDF and 1D-TMDCs nano-additives on the matrix performance. Considering the promising properties of the developed materials, the inexpensive synthetic process, and the extraordinary properties of environmentally friendly and biocompatibe 1D-TMDCs WS2, this work may open up opportunities to produce new PLLA/PVDF hybrid nanocomposites that show great potential for biomedical applications.
Highlights
The biobased, biodegradable aliphatic polyester poly(L-lactic acid) (PLLA) that is derived from natural resources, such as corn and sugar beet, is a highly versatile polymer and a promising alternative to petroleum-derived polymers in many applications as a result of its good biodegradability, renewability, reasonably good mechanical properties, and processability [1,2,3]
For the ternary hybrid PLLA/poly(vinylidene fluoride) (PVDF)/incorporation of 1D (INT) nanocomposites and individual PLLA/INT and PVDF/INT nanocomposites, it was found that the INTs were uniformly dispersed at the nanoscale without evidence of aggregates or agglomerates, verifying the effectiveness of the melt extrusion conditions (Figure 2)
The characteristic peaks of α-form of PLLA in WAXS patterns appeared as soon as the material attained an appreciable degree of crystallinity. The appearance of these peaks relates well to the crystallization temperature calculated from Differential scanning calorimetry (DSC) curves. These results indicate that the presence of INT-WS2 accelerated the crystallization rate of PLLA in the PLLA/PVDF-INT blend nanocomposites
Summary
The biobased, biodegradable aliphatic polyester poly(L-lactic acid) (PLLA) that is derived from natural resources, such as corn and sugar beet, is a highly versatile polymer and a promising alternative to petroleum-derived polymers in many applications as a result of its good biodegradability, renewability, reasonably good mechanical properties, and processability [1,2,3]. Of particular interest is the use of layered transition metal dicalcogenide (TMDC) nanostructures, such as tungsten disulfide (WS2) and molybdenum disulfide (MoS2), which are broadband semiconductors with multidimensional structural anisotropy, 0D (IF), 1D (INT), and 2D [21,22,23,24,25,26] These environmentally friendly and biocompatible TMDCs nanoparticles have demonstratable processing, performance, design, and cost advantages over nanoclays, CNTs, etc. Both the blends and nanocomposites were prepared following the same procedure: each mixture of PVDF and PLLA, with or without INT-WS2, was dispersed in a small volume of ethanol (HPLC grade, Sigma-Aldrich Química SL, Madrid, Spain) and homogenized by mechanical stirring and bath ultrasonication for approximately 15 min. The samples were pressed into films of 0.5 mm thickness in a hot press system using two heating/cooling plates
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