Synthesis and Properties of Hydroxy-Terminated Poly(hydroxyalkanoate)s

This paper describes the biosynthesis and properties of bacterial poly(hydroxyalkanoate)s (PHA) with predominantly hydroxyl end groups. Hydroxy termination is achieved by the addition of low molecular weight diols to the culture. It is found that low molecular weight diols of various structures can be easily incorporated as chain ends, when used during fermentation, by a variety of microorganisms. Incorporation of a chiral diol does not appear to be stereospecific; both (R)- and (S)-1,2-propanediols were incorporated into the polymer. Moreover, both primary and secondary hydroxyl groups of 1,2-propanediol were found to have reacted. It was found that an increase in the hydroxy termination in P(3HB) leads to an increase in the thermal stability, most likely by prolonging the condensation reaction and delaying the degradation reaction.