Melt Chain Dimensions of Polylactide

Melt chain dimensions of two polylactide samples were measured using small-angle neutron scattering. Three polylactides were synthesized:  a deuterated polylactide containing 26% R-stereocenters (d-PLA-26), a hydrogenous polylactide with an R-content similar to the deuterated polylactide (PLA-28), and a hydrogenous polylactide that contained no R-stereocenters (PLA-0). The hydrogenous polylactides were each solution blended with the d-PLA-26 at a volume fraction of 0.2 for the deuterated polymer, and the melt chain dimensions of these polymers were determined. Small-angle neutron scattering experiments were performed at 30 °C for the d-PLA-26/PLA-28 blend and at 200 °C for both the d-PLA-26/PLA-28 and d-PLA-26/PLA-0 blends. Using three analysis methods, the average values for the statistical segment lengths, based on a C₆ repeat unit, were found to be 10.0 ± 0.2 Å for the PLA-28 at 30 °C, 8.9 ± 0.2 Å for the PLA-28 at 200 °C, and 9.9 ± 0.4 Å for the PLA-0 at 200 °C.