Well-Defined Amylose Acetate-graft-polylactide Graft Polymers as Compatibilizers for Renewable Polymer Blends

Regioselectively substituted amylose acetate-graft-polylactide (AmAc-g-PLA) graft polymers were synthesized via grafting-to "click" reaction between C6-azide functionalized AmAc and alkyne-terminated PLA. Alkyne-terminated PLA synthesized through organocatalytic ring-opening polymerization (ROP) permitted control over graft degree of polymerization (DP) and stereochemistry, while azide functionalized AmAc with tailorable C6-azide degree of substitution (DS) allowed graft density control. This describes the first synthesis of polysaccharide-based graft polymers with exclusive C6 grafting and controllable topology. Thermal analysis indicates that glass transition temperatures (T_g) of AmAc and PLA segments are affected after grafting-to coupling, with poly(l-lactide) (PLLA) grafts maintaining crystallizability. AmAc-graft-poly(d,l-lactide) (PDLLA) graft polymers were effective compatibilizers for immiscible blends of starch acetate (StAc) and PDLLA as evidenced by small-angle laser light scattering (SALLS) and phase contrast optical microscopy (PCOM). This method permits the determination of structure-property relationships with regard to the effect of graft polymer topology on blend compatibilization, which will be invaluable in designing compatibilized biobased polymer blends as sustainable materials.