Synthesis and rheology of branched multiblock polymers based on polylactide

To improve the toughness and processability of poly(lactic acid) (PLA), a branched multiblock polymer was prepared from d,l-lactide and ϵ-decalactone. A hydroxy telechelic four-arm star poly(ϵ-decalactone)-poly(d,l-lactide) diblock was synthesized using sequential ring-opening transesterfication polymerization (ROTEP) and coupled using a substoichiometric amount of sebacoyl chloride to obtain a segmented multiblock with a comb-like architecture. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) revealed that this branched multiblock was microphase separated but lacked long-range order. Unlike a linear multiblock of similar mass, the branched material demonstrated significant extensional hardening in the disordered state, suggesting much improved processability in polymer processing methods that require fast elongational flows. Additionally, the branched multiblock material exhibited remarkable tensile toughness. This simple synthetic approach allows for simultaneous control of mechanical and rheological properties using a single macromolecular architecture to address key practical issues with PLA.