A convenient route to PHB macromonomers via anionically controlled moderate-temperature degradation of PHB



The degradation of poly(3-hydroxybutyrate)s in homo- and heterogeneous mixtures with selected salts of organic and mineral acids was investigated. Nonvolatile degradation products, of processes conducted at moderate temperatures (150–170 °C), were analyzed using 1H NMR. Analysis of results revealed a significant decrease in poly([R]-3-hydroxybutyrate) (PHB) thermal stability in the presence of acetic acid and carbonic acid salts of alkali metals (Cs, K, Li) as well as a less substantial effect with respect to bivalent metal (Ca, Mg, Zn) salts. This significant decrease in PHB thermal stability in the presence of salts of weak Bronsted-Lowry acids can be explained in terms of an anionic degradation reaction proceeding via an E1cB mechanism. Furthermore, continuous poly(3-hydroxybutyrate) controlled degradation was developed by a moderate-temperature process using carbonic acid salts as “initiators” of anionic degradation. Foamed PHB macromonomers, bearing one crotonate terminal group, were obtainable via a reactive extrusion process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010