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.

Monomers structurally resembling lignin were prepared by reacting 4-hydroxybenzaldehyde, vanillin, syringaldehyde, (each bio-available) or ethylvanillin (synthetic) with dibromoethane, yielding dialdehydes CHO-Ar-OCH 2 CH 2 O-Ar-CHO. Condensation copolymerization with tetraols catalyzed by paratoluene sulfonic acid yielded polyacetal ethers with cyclic acetals in the case of di-trimethylolpropane (di-TMP) and spirocyclic acetals in the case of pentaerythritol (PTOL). Number average molecular weights (M n ) were in the range of 10 600 to 22 200, although the insolubility of those polymers based on 4-hydroxybenzaldehyde precluded this measurement. The polymers are thermally robust and exhibit 5% mass loss via thermogravimetric analysis in the range of 307-349 C. Those copolymers based on PTOL displayed glass transition (T g ) temperatures (108-152 C) at least 40 C higher than their di-TMP analogues (68-98 C), highlighting the added rigidity conferred by spirocyclic acetals versus cyclic acetals. Preliminary degradation studies were conducted in dimethyl sulfoxide with 0.5% added aqueous HCl (concentrated or 2 M). Dynamic light scattering confirmed the facile hydrolysis of the polymers.Generally, polymer degradation was faster with a higher acid concentration and copolymers from the PTOL tetraol were more resistant to hydrolysis than those from the di-TMP tetraol.

Polyalkylene acetals are synthesized from simple bio-derived diols and diethoxymethane via a novel technique involving interchange of acetal functional groups. This Acetal Metathesis Polymerization (AMP) method provides a route to polyacetals that are designed to degrade under abiotic conditions via simple acidcatalyzed hydrolysis. † Electronic supplementary information (ESI) available: Synthetic details and complete polymer characterization data. See

Potentially sustainable C1 feedstocks carbon monoxide and formaldehyde are subjected to cationic alternating copolymerization to yield polyglycolic acid.