No abstract

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.

A series of Li, Na, Mg, and Ca complexes with 2,6-di-tertbutyl-4-methylphenol (BHT) as the ligand has been synthesized, and their reactivity for the ring-opening polymerization of lactide has been studied. The Ca complex with 2,2′-ethylidenebis(4,6-di-tert-butylphenol) (EDBP) as the ligand also has been synthesized to compare with the BHT systems. All complexes, in the presence of benzyl alcohol as initiator, exhibit high activity for the ring-opening polymerization of lactide. Polymerization activities follow the order of Na ≫ Li > Ca ≫ Mg. Additionally, metal− BHT systems are more efficient than metal−EDBP systems, and this superiority was pronounced in THF solution. Four model metal−BHT complexes with coordinated dimethoxyethane (DME) have been characterized by single-crystal X-ray diffraction. These complexes exhibited a wide variation in the C ipso −O−metal angle (159.3°to 180.0°), and DFT calculations suggested that this flexibility allows the metal to vary its electron density and thereby expedite the catalytic cycle that requires both monomer activation and substrate lability.

Back Cover: Polyalkylenehydroxybenzoates (PAHBs) represent a new class of biorenewable aromatic/aliphatic polyester. These thermoplastics derive from lignin‐based aromatic feedstocks and their thermal properties can be tuned to closely match those of petroleum‐based polyethylene terephthalate. Further details can be found in the communication by L. Mialon, R. Vanderhenst, A. G. Pemba, and S. A. Miller* .