Preparation of Nanocapsules via the Self-Assembly of Kraft Lignin: A Totally Green Process with Renewable Resources

Kraft lignin (KL), the byproduct from the alkali pulping process in the paper industry, is an abundant renewable resource. It was found that KL could be used to form nanocapsules via self-assembly induced by adding water to an ethanol solution of KL. From the results of various imaging techniques and laser light scattering techniques, the hollow sphere feature of this product was confirmed. It was found that there is a higher percentage of ethanol enriched in the interior of the nanocapsules and that the different KL fractions can be spontaneously distributed in the shells according to their hydrophilic–lipophilic sequence. The π–π interactions between the aromatic rings are considered to be an important driving force in the assembly process of the KL nanocapsules. Moreover, the sizes of these KL nanocapsules can vary in the range of tens to hundreds of nanometers, depending on the preparation conditions, which enhance their flexibility to adapt to the potential applications in various fields. Preparation of KL nanocapsules requires only a simple mix of KL/ethanol solution and water, which is a totally green process utilizing a renewable resource.