Easy synthesis of β-O-4 type lignin related polymers

Abstract

The beta-O-4 structure is the most abundant substructure in lignin. Lignin related polymers composed of only the beta-O-4 structure were prepared using simple aromatic compounds as starting materials. Acetophenone derivatives were brominated, polymerized in the presence of K2CO3 and reduced with NaBH4 to give the lignin related polymers. These are linear polymers which resemble natural lignins in their structures, although they do not have a gamma-hydroxymethyl group. The number average degree of polymerization (DPn) was determined with peracetate of the polymers by gel permeation chromatography. The DPn of guaiacyl type polymers ranged from 15.2-21.4, where the value for the syringyl type was 11.3 and for the p-hydroxyphenyl type 16.9. The Guaiacyl type polymer was very soluble in usual lignin solvents such as 1, 4-dioxane-water (96 : 4, v/v) and DMSO, but only slightly soluble in acetone-water (9 : 1, v/v).