Selective nucleation of chitin nanocrystals in the crystallization of poly(ε-caprolactone-b-l-lactide) diblock copolymer composites.

Rod-like chitin nanocrystals (ChNCs) filled biodegradable aliphatic polyesters are of great interest because as-obtained nanocomposites are all-degradable. In this work, we prepared a poly(ε-caprolactone-b-l-lactide) (PCL-b-PLA) copolyester nanocomposite with ChNCs and carried out a crystallization study. The results disclosed that the roles of ChNCs played during crystallization of copolyester matrices were very attractive: as heterogeneous nucleator of PLA phase, whereas as inert filler for PCL phase. Thus, the overall crystallization kinetics of PLA phase were accelerated. The heterogeneous nucleation led to the formation of more amounts of crystallized PLA domains, which favored nucleating following crystallization of PCL phase. In addition, the presence of ChNCs did not strongly influence the microphase-segregated structure of PCL-b-PLA, and had good reinforcements to matrix copolymer. The selective nucleation ability of ChNCs reported in this study is valuable for regulating the structures and properties of nanocomposites based on the ChNCs-filled aliphatic diblock copolyester with double crystalline blocks.