title: Studies on comonomer compositional distribution of bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)s and thermal characteristics of their factions.
abstract: The comonomer-unit compositional distributions have been investigated for bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)] samples with 3HH unit content of 13.8, 18.0, 22.0, and 54.0 mol %. They were comonomer compositionally fractionated using chloroform/n-heptane mixed solvent at ambient temperature. The fractionation of P(3HB-co-18.0 mol %3HH) and P(3HB-co-22.0 mol % 3HH), which could not be carried out effectively at room temperature, were refractionated at 70 degrees C in the mixed solvent. Fractions with different 3HH unit content in a wide range (from 4.4 to 80.7 mol %) were obtained. By use of these fractions with narrow compositional distribution, the comonomer composition dependence of thermal properties was investigated by differential scanning calorimetry. The melting point (T(m)) and heat of fusion (DeltaH) decreased as the 3HH unit content increased in the range of low 3HH content (<40 mol %), while they increased as the 3HH unit content increased in the high 3HH content range (>70 mol %). The minimum T(m) and DeltaH values were found to exist at 3HH unit content of about 60 mol %. The glass transition temperature (T(g)) decreased linearly with the increase of 3HH unit content. The values of T(m), DeltaH, and T(g) of P(3HB-co-3HH)s were compared with those of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and the effects of comonomer types on the thermal properties were revealed.
authors.affiliation: Department of Biomolecular Engineering, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8501, Japan.
authors.forename: Lidan
authors.initials: L
authors.lastname: Feng
authors.forename: Takumi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Kichise
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukuchi
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Chen
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Doi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Inoue
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000737:chemistry* / Q000302:isolation & purification; D001419:Bacteria / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002208:Caproates / Q000737:chemistry* / Q000302:isolation & purification; D005591:Chemical Fractionation; D013696:Temperature; D013816:Thermodynamics; D000094122:Polyhydroxybutyrates
chemical_list: D020155:3-Hydroxybutyric Acid; D002208:Caproates; C115940:poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); D000094122:Polyhydroxybutyrates