Strong Confinement Effects on Homocrystallization by Stereocomplex Crystals in Electrospun Polylactide Fibers

In asymmetric poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) blends, the pre-existing stereocomplex crystals can impose confinement effects on homocrystallization of uncomplexed PLLA among them. However, confinement effects are very weak in the blend films because of relatively large PLLA domains distributed in the skeleton of stereocomplex crystals. As a comparison, in the electrospun blend fibers, fine distribution of uncomplexed PLLA results in strong confinement effects. This is manifested by the significant decrease in the crystallization temperature and melting point. Even so, confinement effects have little influence on the crystal form, and PLLA α-crystals prevail in the electrospun blend fibers after melt crystallization. Finally, confinement effects in the electrospun blend fibers depend on annealing temperatures and almost disappear when the samples are annealed above the melting point of stereocomplex crystals.