Lignin-based polymers and colloids for functional bio-based materials Mohammad Morsali 1 , Adrian Moreno 1,2 , Ievgen Pylypchuk 1 , Mika Sipponen 1 1 Stockholm University, Sweden, 2 Rovira i Virgili University, Tarragona, Spain Developing green and biorenewable materials is a key for a green and sustainable future. Among biorenewable materials, lignin is a wood component and a naturally occurring polyphenol which is responsible for providing the structural endurance and environmental protection to trees and plants. Lignin is available to us as a byproduct of pulp and paper industry and has been considered a low quality waste. Thus, most of the work done on lignin has been focused on its use as a low-value filler in polymer blends and composite materials, or has involved extensive chemical modifications which transform lignin from its original chemical structure. On the other hand, the aromatic backbone of lignin and its naturally occurring functional groups such as carboxyl, phenolic hydroxyl, and aliphatic hydroxyl groups, are great resources that can render lignin-based materials reactive and responsive to different stimuli and make lignin a great candidate as a green replacement for many existing petrol-based phenol based chemicals. Additionally, the amphiphilic character of lignin makes it possible to transform heterogeneous and water insoluble lignin into monodisperse hydrocolloidal dispersions. 1 Herein, we demonstrate straightforward reactions that render lignin plausible for the production of new bulk and colloidal materials of potential industrial interest. Taking advantage of phenolic and aliphatic hydroxyl groups in crude lignin we developed the first one-pot, catalyst free synthesis of lignin vitrimers based on its thermally catalyzed addition reaction with poly(ethylene glycol) divinyl ether (PDV). 2 These lignin-based vitrimers can be used as bulk polymers or adhesives with recoverable dynamic covalent bonds. In their colloidal form, lignin nanoparticles have been studied for multiple potential applications such as reinforcement in polymeric composites, emulsifiers in pickering emulsions and substrates for enzyme immobilization. However, lignin nanoparticles suffer from solubility in organic solvents and high pH media. Using hydroxymethylation chemistry we developed hydrothermally cured lignin nanoparticles which are stable in organic solvents and strongly alkaline media. 3 Taking advantage of this stability and the functional groups present in lignin we showed that it is possible to directly functionalize lignin nanoparticles in colloidal state and synthesize pH-responsive hydrocolloids. Additionally, these stabilized lignin nanoparticles are redox-active and can reduce silver ions forming hybrid lignin- silver nanoparticles with Surface Plasmon Resonance (SPR). It was further demonstrated that the hybrid particles due to their SPR effect can be utilized as colloidal sensors for the detection of hydrogen peroxide. References 1. A. Moreno, J. Liu, M. Morsali and M. H. Sipponen, in Micro and Nanolignin in Aqueous Dispersions and Polymers , eds. D. Puglia, C. Santulli and F. Sarasini, Elsevier, 2022, pp. 385–431. 2. A. Moreno, M. Morsali and M. H. Sipponen, ACS Appl. Mater. Interfaces , 2021, 13 , 57952–57961. 3. M. Morsali, A. Moreno, A. Loukovitou, I. Pylypchuk and M. H. Sipponen, Biomacromolecules , 2022, 23 , 4597–4606.
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© The Author(s), 2021
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