Journal article
Kinetics and mechanism of the monomeric products from abiotic hydrolysis of poly[(R)-3-hydroxybutyrate] under acidic and alkaline conditions
Abiotic hydrolysis of poly[(R)-3-hydroxybutyrate] (PHB) was investigated in acid and base media by monitoring the formation of two monomeric hydrolytic products, 3-hydroxybutyric acid (3HB) and crotonic acid (CA) from three types of PHB matrix, native amorphous granules, precipitates and solvent-cast films.
Control experiments were also performed with five esters of 3-hydroxybutyric acid. The monomeric products were not released from the PHB specimens in acidic solutions (0.1–4N H+), but were measured as the major hydrolytic products from alkaline hydrolysis (0.1–4N OH−). The amorphous PHB granules decomposed 30 times faster than the crystallized PHB precipitates and solvent-cast films.
Formation of both CA and 3HB followed the quasi-0th-order kinetics and their mass ratio (CA/3HB=0.42–0.68) increased with temperature because of the different activation energies, 88.4kg/mol for CA formation and 78.9kJ/mol for 3HB formation. Kinetic analysis and hydrolysis results revealed that dehydration of the 3-hydroxyl group is not a favorable reaction, compared to ester bond hydrolysis, under the chosen experimental conditions.
A transient six-membered ring structure involving two neighboring monomers is most likely needed for crotonate formation.
Language: | English |
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Year: | 2005 |
Pages: | 289-299 |
ISSN: | 18732321 and 01413910 |
Types: | Journal article |
DOI: | 10.1016/j.polymdegradstab.2004.12.026 |