Sustainable polyacetals from erythritol and bioaromatics

The polymerization of biorenewable molecules to polymers with hydrolyzable main-chain functionality is one approach to identifying sustainable replacements for common, environmentally unsound packaging plastics. Bioaromatic polyacetals were synthesized via acid-catalyzed acetal formation from dialdehydes and tetraols. Ethylene linked dialdehyde monomers VV and SS were constructed from bioaromatics vanillin and syringaldehyde, respectively. Tetraol monomers included biogenic erythritol (E), along with pentaerythritol (P), and ditrimethylolpropane (D). Four copolymer series were prepared with varying tetraol content: E/P-VV; E/DVV; E/ P-SS; and E/ D-SS. Number average molecular weights (M-n) ranged from 1,400 to 27,100 Da. Generally, the copolymerization yields were inversely proportional to the feed fraction of erythritol (E), implying that tetraols P and D react more readily. The materials were typically amorphous and exhibited glass transition temperatures (T-g) ranging from 57 to 159 degrees C, suitably mimicking the T-g values of several commodity plastics. The syringaldehyde-based copolymers exhibited a higher T-g range (71-159 degrees C) than the vanillin-based copolymers (57-110 degrees C). Accelerated degradation studies in aqueous HCl (3 M, 6 M, concentrated) over 24 h showed that degradation (M-n decrease) was proportional to the acid concentration. A one-year degradation study of E50/D50-SS (from 50% feed of erythritol) in seawater, deionized water, tap water, or pH 5 buffer showed no M-n decrease; but in pH 1 buffer, the decrease was 40% (18,800 to 11,200). (C) 2016 Wiley Periodicals, Inc.