Studies on comonomer compositional distribution and its effect on some physical properties of bacterial poly(3-hydroxybutyric acid-co-3-hydroxypropionic acid)

Comonomer compositional distribution of bacterially synthesized poly(3-hydr oxybutyric acid-co-3-hydroxypropionic acid) [P(3HB-co-3HP)] was investigate d via solvent/non-solvent fractionation techniques. The result indicates th e presence of extremely broad comonomer compositional distribution in the o riginal bacterial product. Furthermore, utilizing compositionally fractiona ted bacterial copolyesters with much narrower comonomer compositional distr ibutions, the 3HP comonomer content-dependence of their thermal and crystal lization behavior was studied by means of differential scanning calorimeter (DSC) and polarized optical microscopy and the results compared with those of unfractionated copolyesters. It was revealed that the physical features of the fractionated copolyester P(3HB-co-3HP)s strongly depends on the 3HP comonomer content. In addition, to clarify the effect of the compositional distribution on the properties of the unfractionated copolyester, the misc ibility between bacterial poly(3-hydroxybutyric acid) [P(3HB)] and two frac tionated P(3HB-co-3HP) samples with 11.3 and 14.9% 3HP was investigated for blends obtained by solvent casting techniques. The evidence of thermal ana lysis and spherulitic growth rates imply miscibility of the P(3HB)/3HB-rich P(3HB-co-3HP) binary blends. (C) 1999 Society of Chemical Industry.