Thermal properties of poly(3-hydroxy-2-methylbutyrate-co-3-hydroxybutyrate) copolymers with narrow comonomer-unit compositional distributions

Novel polyhydroxyalkanoate (PHA) copolymers of (2R,3R)-3-hydroxy-2-methylbutyrate (3H2MB) and (R)-3-hydroxybutyrate (3HB) [P(3H2MB-co-3HB)] with various comonomer compositions were biosynthesized using recombinant Escherichia coli LSBJ. Furthermore, solvent fractionation of biosynthesized P(24 mol% 3H2MB-co-3HB) was performed to obtain copolymers with narrow comonomer-unit compositional distributions. The melting temperature (Tm) of P(3H2MB-co-3HB) as a function of the comonomer content indicated isodimorphism of the copolymer. The fast crystallization behavior of P(3H2MB) was maintained even when it was copolymerized with 3HB. The P(80 mol% 3H2MB-co-3HB) copolymer, with a Tm close to that of P(3HB), exhibited faster crystallization behavior than the P(3HB) homopolymer. Therefore, copolymerization of 3H2MB and 3HB is valuable for the design of new PHA materials with desirable properties. Polyhydroxyalkanoate copolymers of (2R,3R)-3-hydroxy-2-methylbutyrate and (R)-3-hydroxybutyrate [P(3H2MB-co-3HB)] with various comonomer compositions were biosynthesized using recombinant Escherichia coli. Furthermore, solvent fractionation of P(3H2MB-co-3HB) was performed to obtain copolymers with narrow comonomer-unit compositional distributions. The melting temperature (Tm) of P(3H2MB-co-3HB) as a function of the comonomer content indicated isodimorphism of the copolymer. The fast crystallization behavior of P(3H2MB) was maintained even when it was copolymerized with 3HB. The P(80 mol% 3H2MB-co-3HB) copolymer, with a Tm close to that of P(3HB), exhibited faster crystallization behavior than the P(3HB) homopolymer.