Proton spectra were
recorded at 3001 MHz with a spectrum of 32 K data
points. A total of 64 scans were utilized with a relaxation
delay of 1 s. The Gel Performance Chromatography
(GPC) measurements were taken immediately after poly-
mer extraction to ensure no further degradation with
possible residual organic solvent. Chloroform was utilized
as an eluent at a flow rate of 080 ml min1
with a sta-
bilization pressure of 35 bars and a sample concentration
of 15mgml
1
. A Waters Styragel HT column for mid-
range molecular-mass distributions was used, and sam-
ples of polystyrene with different molecular masses were
used as standard. Differential Scanning Calorimetry
(DSC) experiments were performed on a Perkin-Elmer
Pyris 1 instrument with a dry nitrogen gas flow of
50 ml min1
. The apparatus was calibrated using indium
of high purity. Approximately, 5 mg of the sample was
sealed in an aluminium plate and analysed. The melting
temperature (Tm), melting enthalpy (DHm) and the glass
transition temperature (Tg) were determined by the sec-
ond heating run of DSC endothermic peaks. The crystal-
linity degree (Xc) of PHB was calculated assuming that
the DHm value of 100% crystalline PHB is 146 J g1
(Barham et al. 1984). Scans started at 30°C and were
ramped at 10°C per minute to 230°C.