## 3 Results and Discussion
### Thermal Analysis of PHBV  
The purified PHBV samples and commercial standards were analyzed by DSC to determine their thermal properties (glass transition temperature, \(T_{g}\); melting temperature, \(T_{m}\); crystallization temperature (\(T_{c}\)) and degree of crystallization, \(X_{c}\)); the results obtained from [PERSON] et al. [6] and the reanalyzed data are given in Table 4 and (Supplementary Material Figure S1). The result of \(T_{g}\) of the PHBV samples was similar to the results obtained from [PERSON] et al. [6] (\(-0.7\)\({}^{\circ}\)C to \(-7.4\)\({}^{\circ}\)C vs. \(-2.8\)\({}^{\circ}\)C to \(-10\)\({}^{\circ}\)C) consistent with commercial PHBV (22% HV, \(-1.5\)\({}^{\circ}\)C). The result of \(T_{m1}\) and \(T_{m2}\) of the PHBV samples was similar to the results obtained from [PERSON] et al. [6], except PHBV-61 and -71 which showed one melting peak. Isomorphism phenomena can lead to the presence of two melting peaks [6; 31]. As PHBV presents a semi-crystalline structure the crystals with higher HV content will have a higher amorphous phase ratio and thus during heating will be melted (\(T_{m1}\)) first. In crystals with lower HV content, the crystallinity ratio is higher, so the crystals will melt at a higher temperature (\(T_{m2}\)) [31; 46]. Other factors that contribute to two melting points include the different crystalline morphologies (thickness, perfection, lamellar stability, or distribution), crystallites of different molar masses, physical aging, and amorphous phase relaxation [31; 46]. There was no correlation between the melting temperature of the polymers and 3 HV content. The \(X_{c}\) of the purified PHBV obtained from first cooling cycle which was slightly higher than that obtained from [PERSON] et al. [6] (16.6-29% vs. 13.9-25%). The \(I_{C=O}\) of all the extracted PHBV samples ranged between 2.01 to 2.59 which was higher than the previously reported value of 0.949 for PHB [47]. PHB was shown to have a higher \(X_{c}\) (61%), by X-ray diffraction, than PHBV (36.2%) and also showed higher value of \(I_{C=O}\) by FTIR (3.8 vs. 2.7) [26]. The values of \(I_{C=O}\) by FTIR and \(X_{c}\) by DSC of the extracted PHBVs gave a poor correlation (\(R^{2}\) = 0.53). The \(T_{c}\) for the extracted PHBVs ranged from 56 to 107 \({}^{\circ}\)C (Table 4). Sample PHBV-32 showed the highest \(T_{c}\) (107.1 \({}^{\circ}\)C) with a 3 HV content of 0.18 while sample PHBV-71 had the lowest \(T_{c}\) (56.5 \({}^{\circ}\)C) and a higher 3 HV content of 0.23. There was a negative linear correlation between \(T_{c}\) and 3 HV content (\(R^{2}\) = 0.54), and also between \(T_{c}\) and \(X_{c}\) of the extracted PHBVs (\(R^{2}\) = 0.54). An Increase in 3 HV content results in an increase in the amorphous phase and thus leads to a reduction in \(X_{c}\) and \(T_{c}\)[48]. A lower \(T_{c}\) indicates that the complete crystallization takes a longer time [49]. PHBV-15 has the lowest 3 HV content (0.16), high \(X_{c}\) (29%), and low \(T_{c}\) of 62 \({}^{\circ}\)C. This can be attributed to the higher _PDI_ of 1.43 in PHBV-15. Higher _PDI_ indicates a larger size distribution of polymer chains. Shorter chains need less time for crystallization compared to longer chains which results in reduction of \(T_{c}\)[49]. A \(T_{c}\) value ranging from 41 to 82 \({}^{\circ}\)C for CHCl\({}_{3}\) extracted PHBV with 3 HV contents