High Value Use of Technical Lignin. Fractionated Lignin Enables Facile Synthesis of Microcapsules with Various Shapes: Hemisphere, Bowl, Mini-tablets, or Spheres with Single Holes
Yuxiao Cui, Martin Lawoko, Anna J. Svagan
Abstract
Anisotropic carbon-rich microcapsule morphologies are of great value in many applications including catalysis, energy storage, biomedicine, and osmosis-triggered drug delivery, due to an observed shape effect. However, high-precision synthesis, to generate large yields of well-defined anisotropic shapes, is generally challenging. Here, we show for the first time that a modified carbon-rich waste-material, a fractionated and acetylated Kraft lignin, enables facile production of large amounts of well-defined “acorn-like” microcapsules with heterogeneous shell thicknesses. This is due to the inherent physicochemical properties of the fractionated lignin at the oil/water (O/W) interface. The acorn-shape is strongly related to two distinct lignin-molecule populations, that phase separate during microcapsule formation. Fine-tuning the post-treatment conditions (pressure or hydrothermal temperature) results in a number of different microcapsule shapes; hemisphere, bowl, mini-tablets, or spheres with single holes. Further chemical modification to their surfaces is also demonstrated. The present study provides a new library of shape-anisotropic carbon-rich building blocks that open new avenues for assembling hierarchical material with a high level of complexity.