Abstract
Polymers made from natural biomass are gaining interest due to the rising environmental concerns and depletion of petrochemical resources. Lignin isolated from lignocellulosic biomass is the second most abundant natural polymer next to cellulose. The paper pulp process produces industrial lignin as a byproduct that is mostly used for energy and has less significant utility in materials applications. High abundance, rich chemical functionalities, CO2 neutrality, reinforcing properties, antioxidant and UV blocking abilities, as well as environmental friendliness, make lignin an interesting substrate for materials and chemical development. However, poor processability, low reactivity, and intrinsic structural heterogeneity limit lignins′ polymeric applications in high-performance advanced materials. With the advent of controlled polymerization methods such as ATRP, RAFT, and ADMET, there has been a great interest in academia and industry to make value-added polymeric materials from lignin. This review focuses on recent investigations that utilize controlled polymerization methods to generate novel lignin-based polymeric materials. Polymers developed from lignin-based monomers, various polymer grafting technologies, copolymer properties, and their applications are discussed.
Highlights
Lignin is a heterogenous phenylpropanoid macromolecule with a three-dimensionally branched architecture composed of random crosslinks of monomeric units called monolignols
The results indicated that high-performance dispersants are obtained through a grafted architecture using of acrylamide prepared via and free radical polymerization (FRP)
Figure illustrates the from organosolv lignin and an isocyanate-terminated poly(propylene oxide) macromonomer catalyzed polyurethane synthesisas from organosolv ligninetand an isocyanate-terminated poly(propylene oxide) by dibutyltin dilaurate reported by Gandini al. [128]
Summary
Lignin is a heterogenous phenylpropanoid macromolecule with a three-dimensionally branched architecture composed of random crosslinks of monomeric units called monolignols. The advances of biorefineries that convert cellulosic biomass into liquid transportation fuels will eventually create a surplus of industrial lignin [5]. Chemical corporations such as Ingevity Corporation has been producing high-quality kraft lignin, i.e., Indulin AT, for many decades. Lignin-based materials and chemicals represent potential value-added products as (1) macromolecule additives or polymer blends; (2) fragmented aromatic compounds such as benzene, toluene, xylenes;. Lignin-based polymeric materials can be developed by blending lignin with commercial off the shelf polymers. Benefits such as improved thermal and mechanical properties for such blends have been reported. This review attempts to gather recent developments in lignin polymer chemistry with a focus on controlled polymerization methods
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