3D printing by fused deposition modelling (FDM) enables rapid prototyping and fabrication of parts with complex geometries. Unfortunately, most materials suitable for FDM 3D printing are non-degradable, petroleum-based polymers. The current ecological crisis caused by plastic waste has produced great interest in biodegradable materials for many applications, including 3D printing. Poly(lactic acid) (PLA), in particular, has been extensively investigated for FDM applications. However, most biodegradable polymers, including PLA, have insufficient mechanical properties for many applications. One approach to overcoming this challenge is to introduce additives that enhance the mechanical properties of PLA while maintaining FDM 3D printability. This review focuses on PLA-based nanocomposites with cellulose, metal-based nanoparticles, continuous fibers, carbon-based nanoparticles, or other additives. These additives impact both the physical properties and printability of the resulting nanocomposites. We also detail the optimal conditions for using these materials in FDM 3D printing. These approaches demonstrate the promise of developing nanocomposites that are both biodegradable and mechanically robust.

Metrics & MoreArticle RecommendationsCONSPECTUS: Nanotubes offer a unique combination of structural precision, tunable interior environments, and high aspect ratios that will be useful for many applications. Despite these desirable attributes, widespread explorations into the properties and applications of chemically designed nanotubes have been limited by challenges related to their synthesis. This realization has motivated developing a unified synthetic nanotube design, which would enable wide-reaching explorations into onedimensional molecular architectures. In principle, supramolecular polymerization is a viable method to prepare such systems, but historically, this approach has yielded materials with poor mechanical properties and/or low aspect ratios whose chemical diversity is limited. This Account describes the development of an acid-mediated approach to macrocycle assembly that overcomes these limitations to yield robust, yet reversible, high-aspect-ratio nanotubes. Imine-linked macrocycles are prepared in high yield from readily accessible precursors by coupling dynamic imine exchange to an out-of-equilibrium macrocycle stacking event. Upon protonation, these macrocycles assemble into high-aspect-ratio nanotubes through electrostatic, solvophobic, and π−π interactions. The interplay between covalent and noncovalent processes are critical to guide macrocycle synthesis and assembly. Including basic pyridine groups into the macrocycle backbone leads to cooperative assembly, even in the presence of <1 equiv of acid per macrocycle. This design was elaborated to enable a general onepot nanotube synthesis from many functional aromatic dialdehydes. The development of structure−property relationships for nanotube assembly strength and ion conductivity are made possible because protonation-induced macrocycle assembly is modular and robust. For instance, supramolecular interactions endow synthetic nanotubes with robust cohesion and mechanical properties that surpass many covalent linear polymers. Tailoring the nanotube interior using site-selective chemical functionalization results in ion-conducting materials. Pyridinium-based nanotubes universally exhibit the ability to conduct protons and nanotubes functionalized with interior glycol groups promote efficient Li-ion transport. Overall, this versatile class of one-dimensional nanostructures shows substantial promise to merge the desirable properties of carbon nanotubes and biological filaments, all while being synthetically tailorable for many designed applications.

No abstract

No abstract