Effect of poly(ethylene glycol)-block-poly(L-lactide) on the poly[(R)-3-hydroxybutyrate]/poly(L-lactide) blends

Compatibility of the poly[(R)-3-hydroxybutyrate] (PHB)/poly(L-lactide) (PLLA) blend was investigated, with and without compatibilizer. PHB and PLLA were shown to be compatible, as long as the molecular weight of PLLA was 11,700 g/mol or less. However, when the molecular weight of PLLA was 56,000 (56K) or 190,000 (190K) g/mol, PLLA was incompatible with PHB. Mechanical properties of the PHB/56K PLLA blends containing PEG-b-PLLA copolymer or PVAc as compatibilizer were not improved very much. It was conceived that the PEG-b-PLLA copolymer was mixed into the parent polymer, rather than being located in the interphase between PHB and PLLA.