A new type of phenolic lignin-based network polymer with the structure-variable function composed of 1,1-diarylpropane units

Abstract

Phenolic lignin-based network polymers with structure-variable func-tion have been designed, and a reaction process has been developed for synthesizing them directly from native lignins. The process includes a phase-separation reaction system composed of phenol derivatives and concentrated acid. The key point of the process is that lignin and carbohydrates, which form an interpenetrating polymer network within the cell wall, are separated into different phases and their modifications are controlled individually. The resulting lignin-based polymers (lignophenol derivatives) have unique functions, which conventional lignins do not have, in spite of retention of the original interunit linkages: these include highly phenolic property, no conjugated system, light colour comparable with native lignin, structure-variable function and solid–liquid transformation. These original functions are due to the selective hybridization of lignin structural units with monomeric phenol derivatives at Cα positions, leading to network structures composed mainly of 1,1-diarylpropane-type units. New types of applications of lignophenol derivatives using their original functions are described (biocatalyst system and lignin–fibre composites). © 1998 Society of Chemical Industry