Fully bio-renewable multiblocks copolymers of poly(lactide) and commercial fatty acid-based polyesters polyols: Synthesis and characterization

The present work deals with the synthesis and characterization of novel multiblock copolymers containing poly(lactide) (PLA) and fatty acid dimer-based polyols. Notably, both blocks are bio-renewable. PLA segments are rigid and crystallizable, while the polyol-blocks are amorphous and possess low glass transition temperature. The synthetic procedure consists of two successive steps. In the first, PLA oligomers terminated with hydroxyl groups, having a molar mass of about 8000 g/mol, are prepared and characterized with NMR and GPC. The second steps involves the coupling of PLA and the (commercially available) polyol by means of 1,6-hexamethylene diisocyanate. The product of the chain-extension reaction is subsequently characterized by NMR, FT-IR spectroscopy, GPC, TGA and DSC. These analyses allowed us to confirm the occurrence of chain coupling and the total inclusion of the fatty acid-based polyol in the copolymer. The chain architecture is thus characterized by a multiblock structure, with random arrangement of PLA and polyol segments. The two blocks are immiscible, poly(lactide) segments preserve their crystallizability, notwithstanding the covalent linkage with amorphous polyol. Blends of multiblocks based on oppositely configured l- and d-poly(lactide) exhibit complete stereocomplexation, independent of soft block content in the copolymer. The inclusion of fatty acid dimer-based polyols in PLA modifies its surface wettability, increasing the hydrophobicity of the material.