Metal oxide microparticles with well-defined internal mesostructures are promising materials for a variety of different applications, but practical routes to such materials that allow the constituent structural length scales to be precisely tuned have thus far been difficult to realize. Herein, we describe a novel platform methodology that utilizes self-assembled block copolymer (BCP) microparticles synthesized by dispersion polymerization in supercritical CO2 (scCO2) as universal structure directing agents for both hydrolytic and non-hydrolytic sol-gel routes to metal oxides. Spherically structured poly(methyl methacrylate-block-4-vinyl pyridine) (PMMA-b-P4VP) BCP microparticles are translated into a series of the corresponding organic/inorganic composites and pure inorganic derivatives with a high degree of fidelity for the metal oxides TiO2 and LiFePO4. The final products are comprised of particles close to 1 μm in size with a highly ordered internal morphology of interconnected spheres between 20 -40 nm in size. Furthermore, our approach is readily scalable, enabling grams of pure or carbon coated TiO2 and LiFePO4, respectively, to be fabricated in a facile two step route involving ambient temperature mixing and drying stages. Given that both length scales within these BCP microparticles can be controlled independently by minor variations in the reagent quantities used, the present general strategy could represent a milestone in the design and synthesis of hierarchical metal oxides with completely tunable dimensions.
It is widely accepted that moving from a linear to circular
economy
for plastics will be beneficial to reduce plastic pollution in our
environment and to prevent loss of material value. However, challenges
within the sorting of plastic waste often lead to contaminated waste
streams that can devalue recyclates and hinder reprocessing. Therefore,
the improvement of the sorting of plastic waste can lead to dramatic
improvements in recyclate quality and enable circularity for plastics.
Here, we discuss current sorting methods for plastic waste and review
labeling techniques to enable enhanced sorting of plastic recyclates.
Photoluminescent-based labeling is discussed in detail, including
UV–vis organic and inorganic photoluminescent markers, infrared
up-conversion, and X-ray fluorescent markers. Methods of incorporating
labels within packaging, such as extrusion, surface coatings, and
incorporation within external labels are also discussed. Additionally,
we highlight some practical models for implementing some of the sorting
techniques and provide an outlook for this growing field of research.
We report the synthesis of phase separated PMMA-b-PS-b-P4VP microparticles via RAFT-mediated dispersion polymerisation in scCO2 and their use as a structure-directing agent for the fabrication of TiO2 microparticles for photocatalysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.