Acetyl Cellooligosaccharide-Based Block Copolymers for Toughening Cellulose Triacetate/Poly(ε-caprolactone) Biodegradable Blends

Although brittle, cellulose acetate is a highly promising next-generation environmentally benign material. However, toughening it without deteriorating its biodegradability is challenging. This study reports on the design and synthesis of a block copolymer (BCP) comprising cellooligosaccharide triacetate and poly(epsilon-caprolactone) (PCL) as a compatibilizer for the cellulose triacetate (CTA) and PCL blend. PCL is an ideal blend partner due to its softness and biodegradability. BCPs with different architectures such as AB, ABA, and A2BA2 types (A, cellooligosaccharide triacetate; B, PCL) were prepared by Cu-catalyzed azido-alkyne click reactions of azido-functionalized PCLs and propargyl-functionalized cellooligosaccharide triacetate. CTA/PCL/BCP ternary blend films were prepared by solvent casting, followed by hot pressing. These films had better mechanical properties than those of neat-CTA and CTA/PCL binary blend films. ABA- and A2BA2-type BCPs were particularly effective, probably because they could form a loop structure of the PCL block in the PCL domain, leading to improved stability at the interface. Atomic force microscopy revealed that the improved interfacial adhesion between the CTA matrix and PCL domain mediated by BCPs is the dominant factor for improving mechanical performance, rather than improving the dispersion of the PCL domain. Our study results may help in expanding the potential applications of cellulose acetate without compromising its biodegradability.