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Comonomer Compositional Distribution and Thermal and Morphological Characteristics of Bacterial Poly(3-hydroxybutyrate- c o -3-hydroxyvalerate)s with High 3-Hydroxyvalerate Content

2001; American Chemical Society; Volume: 2; Issue: 4 Linguagem: Inglês

10.1021/bm010128o

1526-4602

Yi Wang, Shino Yamada, Naoki Asakawa, Tsuneo Yamané, Naoko Yoshie, Yoshio Inoue,

Polymer crystallization and properties

The comonomer compositional distribution and thermal and morphological characteristics were investigated for five bacterially synthesized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] samples with 3HV content of 45, 49, 70, 80, and 96 mol %. All these samples were fractionated into many fractions with widely different 3HV content by changing solvent/nonsolvent volume ratio of chloroform/n-heptane mixtures. Bacterial P(3HB-co-3HV) samples investigated in this study were found to have broad comonomer compositional distribution. The tendencies of the fractional precipitation of the P((3HB-co-3HV)s with 3HV content lower than 60 mol % and those with 3HV higher than 80 mol % were found to be contrary. The 3HV content dependences of the thermal properties and crystalline structures were investigated for bacterial poly(3-hydroxybutyrate) [P(3HB)] and a series of compositionally well-fractionated P(3HB-co-3HV) samples with 3HV content ranged from 14 to 98 mol % by DSC, WAXD, and solid-state 13C NMR. It was found that P(3HB-co-3HV) samples with 3HV content lower than about 47 mol % form the crystalline lattice having the P(3HB) homopolymer type lattice including the 3HV unit as the crystal constituent, and those with a 3HV content higher than about 52 mol % form the crystalline lattice having the P(3HV) homopolymer type lattice including the 3HB units. Thus, P(3HB-co-3HV)s show the crystalline structural change in a very narrow range of 3HV content.