Abstract
Recyclable lignin-based materials, lignophenols were synthesized directly from native lignins, using the phase-separation system composed of phenols and concentrated aci(L Under alkalioe condition C1-phenoxide of 1, 1-bis(aryl)propane type units attacked adjacent C2, followed by the cleavage of ayl ether linkages (switehing function). Although ligno-p-cresol and ligno-2, 4-dimethylphenol had similar structural characteristics and depolymerization patterns, ligno-p-cresol with a reaction site on cresolic nuclei was hydroxymethylated to a larger extent than ligno-2, 4-dimethylphenol: the amount of introduced hydroxymethyl group was 0.81mol/C9 in ligno-p-cresol, 0.15mol/C9 in ligno-2, 4-dimethylphenol. Hydroxymethylated ligno-p-cresol and ligno-2, 4-dimethylphenol were polymerized by heating to give a network type- and a linear type-polymers, respectively. The resulting polymer chains were cleaved at the switching points to give low molecular weight subunits by the alkaline treatment.
