Density measurements also support this proposal. Thedensity of the amorphous PHA is 1.177 g cm−3and of thecrystalline phase is 1.260 g cm−3[160]. Barker et al. [207]showed that the density of P(3HB-co-3HV) in both thecrystalline and amorphous states decreased as HV contentincreased. Assuming that the degree of crystallinity of thecopolymers of different HV content is similar, then theremust be partial exclusion of HV units from the crystals[207]. Mitomo and Doi [195] isolated the crystalline coreusing aminolysis (with 20% methylamine), and showedthat the HV content of the core was smaller than the over all content in P(3HB-co-3HV) copolymer, indicatingsome exclusion of HV.