Carbon Nanotube Grafted Poly(l-lactide)-block-poly(d-lactide) and Its Stereocomplexation with Poly(lactide)s: The Nucleation Effect of Carbon Nanotubes

Multiwalled carbon nanotube (CNT) grafted poly(l-lactide)-block-poly(d-lactide) copolymer (CNT-L-D) was synthesized by ring opening polymerization of d-lactide on the end hydroxyls of poly(l-lactide) (PLLA) prepolymers grafted on the surface of CNT. The stereocomplexation of solution cast and melt crystallized CNT-L-D, PLLA/CNT-L-D, and PDLA/CNT-L-D blends were investigated by differential scanning calorimetry, wide-angle X-ray diffraction, and optical microscopic observation. Solution cast and melt crystallized CNT-L-D copolymer form exclusive stereocomplex (sc) crystallites. The melting temperature, normalized crystallinity, and the fraction of sc crystallites for both solution cast and melt crystallized PDLA/CNT-L-D blends are higher than those of PLLA/CNT-L-D blends, indicating distinct stereocomplexation mechanisms in both blends. The heterogeneous nucleating effect of CNT makes the PLLA block grafted directly on CNT always participate in sc crystallite formation. So, for PDLA/CNT-L-D blends, the ste...