Biosynthesis and Properties of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Polymers

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• 作者：Jawed Asrar ; Henry E. Valentin ; Pierre A. Berger ; Minhtien Tran ; Stephen R. Padgette ; and Joel R. Garbow
• 刊名：Biomacromolecules
• 出版年：2002
• 出版时间：September 2002
• 年：2002
• 卷：3
• 期：5
• 页码：1006 - 1012
• 全文大小：185K
• 年卷期：v.3,no.5(September 2002)
• ISSN：1526-4602

文摘

In support of programs to identify polyhydroxyalkanoates with improved materials properties, we report onour efforts to characterize the mechanical and thermal properties of copolyesters of 3-hydroxybutyrate (3HB)and 3-hydroxyhexanoate (3HHx). The copolyesters, having molar fraction of 3HHx ranging from 2.5 to 35mol % and average molecular weights ranging from 1.15 × 10⁵ to 6.65 × 10⁵, were produced by fermentationusing Aeromonas hydrophila and a recombinant strain of Pseudomonas putida GPp104. The polymers werechloroform extracted and characterized by solution-state and solid-state nuclear magnetic resonance (NMR)spectroscopy and a variety of mechanical and thermal tests. Solution-state ¹H NMR data were used todetermine polymer composition-of-matter, while solution-state ¹³C NMR data provided polymer-sequenceinformation. Solvent fractionation and NMR spectroscopic characterization of these polymers showed thatpolymers containing up to 9.5 mol % 3HHx had a Bernoullian compositional distribution. By contrast,polymers containing more than 9.5 mol % 3HHx had a bimodal polymer composition. Solvent fractionationof these 3HHx-rich polyesters produced two polymer fractions, each of which was again consistent withBernoullian polymerization statistics. Solid-state NMR relaxation experiments provided insight into agingin poly(3HB-co-3HHx) copolymers, demonstrating increased polymer-chain motion with increasing 3HHxcontent. The elongation-to-break ratio in the polyesters increased with increasing molar fraction of 3HHxmonomers. Aging properties of the poly(3HB-co-3HHx) copolymers were very similar to copolymers of3HB and 3-hydroxyvalerate (3HV). However, poly(3HB-co-3HHx) exhibited increased activation energyto thermal degradation with increasing 3HHx content.