Poly(d-lactide)-poly(menthide)-poly(d-lactide) (PDLA-PM-PDLA) triblock copolymers were explored as novel nucleating agents for the crystallization of poly-(l-lactide) (PLLA). PLLA/PDLA-PM-PDLA blends containing ≥85 wt% PLLA were prepared in a batch melt mixer. SAXS analysis was consistent with the ability of PDLA-PM-PDLA to form micelles when mixed with atactic polylactide. The presence of the stereocomplex in the PLLA matrix was confirmed by differential scanning calorimetry (DSC). The effectiveness of the putative stereocomplexed micelle crystallites for nucleating PLLA crystallization was also confirmed by DSC. Nucleation efficiencies near 100% were obtained when using a triblock copolymer with 15 kg/mol PDLA end blocks. In addition, fast crystallization kinetics were observed in isothermal crystallization experiments at 140°C. Compared to PLLA/PDLA homopolymer blends, improvements in nucleation efficiency were observed when blending PLLA with PDLA-containing triblock copolymers.
- Differential scanning calorimetry (DSC)