Polyalkylenehydroxybenzoates (PAHBs): Biorenewable Aromatic/Aliphatic Polyesters from Lignin

Polyalkylenehydroxybenzoates (PAHBs) are a new class of thermoplastic, biorenewable aromatic/aliphatic polyester having the general formula H-[O-(CH2)n-O-4-(3-X, 5-Y-C6H2)-CO]z-OH. These are synthesized from the lignin-derived aromatics 4-hydroxybenzoic acid (X = Y = H), vanillic acid (X = OMe; Y = H), and syringic acid (X = Y = OMe). Alkylation of these with several chloroalkanols affords hydroxy-acid monomers suitable for polyesterification under dynamic vacuum between 150 and 250 °C with 1 mol% Sb2O3 as catalyst. Thus, polyalkylene 4-hydroxybenzoates, polyalkylene vanillates, and polyalkylene syringates are prepared, characterized, and subjected to thermal property comparisons by differential scanning calorimetry and thermogravimetric analysis.