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This work summarizes the miscibility and transport properties of different polymer blends obtained by mixing a bacterial, isotactic poly(3-hydroxybutyrate) (iPHB) with copolymers of styrene and vinyl phenol (Sty-co-VPh copolymers). Given that iPHB and pure commodity poly(styrene) (PS) form immiscible blends, PS has been modified by copolymerizing it with vinyl phenol (VPh) units, in an attempt to promote blend miscibility. VPh units have appropriate functional groups that interact with iPHB ester moieties. The potential miscibility was investigated by differential scanning calorimetry (DSC) measuring the glass transition temperatures of blends of different compositions. As an additional test, the interaction parameter between the two components, using the iPHB melting point depression caused by the second component, was also measured. Copolymers containing less than 90% styrene showed miscibility with iPHB.Given the remarkable barrier properties of iPHB to gases and vapours, the study has been completed by measuring transport properties of carbon dioxide through different iPHB/Sty-co-VPh copolymer blends, using gravimetric sorptions in a Cahn electrobalance. A clear difference was observed between the behaviour of rubbery blends and those that exhibit a glassy behaviour at the selected experimental temperature (303 K). [Copyright &y& Elsevier]

In this work a Fourier transform infrared (FTIR) study of blends of styrene–vinyl phenol copolymers (containing different proportions of styrene) with atactic PHB is presented. The equilibrium constant describing phenolic OH/ester carbonyl hydrogen bonds (KA) has been experimentally determined from the quantification of the hydrogen-bonded carbonyl group fraction as a function of temperature, and the effect of functional group accessibility on KA values has been discussed. An average value of KA=41 has been employed to perform a prediction of miscibility maps employing the association model of Painter and Coleman. A fairly good agreement between theoretical predictions and experimental results has been obtained. [Copyright &y& Elsevier]