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/D-VV; 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 °C, suitably mimicking the T_g values of several commodity plastics. The syringaldehyde-based copolymers exhibited a higher T_g range (71–159 °C) than the vanillin-based copolymers (57–110 °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). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44089.

The ability of an alkyl branch to depress the melting temperature in a polyoxymethylene chain is measurably less than that in a polyethylene chain. The factors that inhibit the alkyl-branch plasticization of polyoxymethylene are considered by computational assessment of a series of model compounds at various levels of theory: DFT B3LYP 6-31+G*, DFT B3LYP 6-311++G**, MP2 cc-pVTZ, T1, and G3(MP2). Intramolecular interactions—characterized as acetal CH···O hydrogen bonds—are surprisingly strong and likely encourage conformational regularity in the vicinity of the alkyl branches, allowing maintenance of the intermolecular chain-chain interactions. The acetal CH···O hydrogen bonds in dimethylene glycol average to 2.65 kcal/mol while the non-acetal CH···O interactions in 1,3-propanediol are much weaker with an average of 0.34 kcal/mol (G3(MP2)). The related, classical OH···O hydrogen bond in ethylene glycol is found to be worth 2.12 kcal/mol. To describe this energetic ordering, an additional stabilizing anomeric effect is invoked for dimethylene glycol, a model for polyoxymethylene.