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Sequence distribution in microbial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) co-polyesters determined by NMR and MS.

Zagar E, Krzan A, Adamus G, Kowalczuk M

National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia. ema.zagar@ki.si

The microstructure of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolyesters (PHBV) as well as a mixture of two PHBV copolyesters of different comonomer composition and sequence distribution was studied by 13C NMR based on dyad and triad analysis and multistage electrospray ionization mass spectrometry (ESI-MSn). Both techniques gave results that were in good agreement for all investigated samples. The effect of microstructure on PHBV thermal properties was investigated from the melting behavior of samples. A PHBV copolyester with randomly distributed hydroxyvalerate units (12.0 mol % HV) showed a single melting peak, whereas samples with nonrandom composition distribution showed multiple melting peaks in their thermograms. Such complex melting behavior suggested that the 12.9 and 27.1 mol % PHBV copolyesters were actually blends of several copolymers with widely different comonomer-unit composition.

Published 10 July 2006 in Biomacromolecules, 7(7): 2210-6.
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