Synthesis and properties of hydroxy-terminated poly(hydroxyalkanoate)s

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