Chirality Effect on Flory-Huggins Interaction Parameters in Polylactide-$b$-Poly(ethylene-\textit{co}-1-butene)-$b$-Polylactide Triblock Copolymers*

In this work, a set of well-defined polylactide-$b$-poly(ethylene-\textit{co}-1-butene)-$b$-polylactide (PLA-PEB-PLA) triblock copolymers were synthesized by controlled ring-opening polymerization of corresponding lactide monomers (L-lactide and racemic mixture of D- and L-lactides) using Sn(Oct)$_{2}$ as the catalyst. The volume fractions of PLA in the triblock copolymers were adjusted by tuning its molecular weight. The mesophase morphology and phase transitions in these triblock copolymers were studied by temperature-dependent small-angle X-ray scattering (SAXS). The Flory-Huggins interaction parameter $\chi $ between EB and lactide as a function of temperature were estimated from the order-disorder transition temperature (T$_{ODT})$ using the mean-field critical ($\chi $N)$_{c}$ values. The effects of PLA chirality on both Flory-Huggins interaction parameter and segmental lengths were investigated.