Enhanced Self-Assembly and Mechanical Properties of Cellulose-Based Triblock Copolymers: Comparisons with Amylose-Based Triblock Copolymers

Herein, we compared the microphase-separation behavior and mechanical properties of cellulose- and amylose-based block copolymers (BCPs). Various cellooligosaccharide triacetate-b-poly(delta-decanolactone)-b-cellooligosaccharide triacetates (AcCel(n)-b-PDL-b-AcCel(n)s), which are cellulose-based ABA-type BCPs, with PDL molecular weights of approximately 5, 10, and 20 kg mol(-1) and PDL volume fractions of 0.65, 0.77, and 0.87, were synthesized from alpha,omega-diazido-end-functionalized PDLs and propargyl-end-functionalized cellooligosaccharide triacetates via click chemistry. We adopted the cellodextrin-phosphorylase-mediated oligomerization of alpha-D-glucose-1-phosphase in the presence of a propargyl-end-functionalized cellobiose primer to synthesize the functional cellooligosaccharide segment. The maltooligosaccharide triacetate-b-poly(delta-decanolactone)-b-maltooligosaccharide triacetate (AcMal(n)-b-PDL-b-AcMal(n)s) amylose counterparts were also synthesized in a similar manner. Small-angle X-ray scattering experiments and atomic force microscopy revealed that AcCel(n)-b-PDL-b-AcCel(n)s are more likely to microphase-separate into ordered nanostructures compared to AcMal(n)-b-PDL-b-AcMal(n)s, despite their comparable chemical compositions and molecular weights. Furthermore, AcCel(n)-b-PDL-b-AcCel(n)s exhibited significantly superior mechanical performance compared to their amylose counterparts under tensile testing, with Young's modulus and stress at break of AcCel(n)-b-PDL10k-b-AcCel(n) being 2.3 and 1.8 times higher, respectively, than those of AcMal(n)-b-PDL10k-b-AcMal(n). The enhanced microphase-separation and mechanical properties of AcCel(n)-b-PDL-b-AcCel(n)s were found to be attributable to the stiffness and crystalline nature of the AcCel(n) segments. These results demonstrate the advantages of using cellulose derivatives to synthesize novel biofunctional materials.

Automated summary

In this study, the microphase-separation behavior and mechanical properties of cellulose- and amylose-based block copolymers were compared. It was found that cellulose-based block copolymers are more likely to form ordered nanostructures and show superior mechanical performance under tensile testing compared to amylose counterparts. This enhanced performance was attributed to the stiffness and crystalline nature of the cellulose segments.