Sequential transformation and utilization of natural network polymer “LIGNIN”

Abstract

Lignin is the most abundant and complicated natural polymer, forming long-term carbon flow in the ecosystem. Lignin is composed of phenyl propane units which are the combination of glycerol- and polyhydric phenol units. A key for sequential functionality control is how to control C1- (7%) and C2- (50%) aryl ethers selectively. The cleavage of C1 aryl ethers results in the transformation of polymer structures from network to linear-type, and that at C2 leads to depolymerization to dimer–oligomer level. The originally designed sequential transformation system includes two steps: 1st step; the selective control of C1 structures to give 1,1-bis(aryl)propane type units, leading to the standardization of C1 functionality, 2nd step; the selective control of C2 structures using intramolecular switching devices [1,1-bis(aryl)propane-2-O-aryl ether units], leading to the change of molecular weight and phenolic activity. The polymers, lignophenols, derived from native lignin through C1 control are multi-functional lignin-based materials, linear types of lignin subunits with phenol derivatives at C1. Sequential applications have been designed originally.