Copolymers of poly(3-hydroxyoctanoates) (PHAs) containing repeating units with unsaturated or brominated pendant side chains have been obtained from cultures of Pseudomonas oleovorans grown on mixtures of octanoic acid and undecenoic acid or 11-bromoundecanoic acid as carbon sources. These polymers, bearing reactive functionalities, have been used to graft acetylated maltosyl units either by anti-Markovnikov addition to the double bond or S(N)2 substitution of the halogen. De-O-acetylation of the sugar moieties yielded PHAs with new properties.