Synthesis and Self-Assembly of Oligomeric Cellulose-block-Poly(ethylene glycol) Diblock Copolymers

Block copolymers containing cellulose have not been well studied or understood partly due to the poor solubility of cellulose in common solvents. In this study, well-defined oligomeric cellulose-block-poly(ethylene glycol) diblock copolymers, Cell_1.1k-b-PEG_1.7k (M_n = 2.8 kD, PDI = 1.04) and Cell_1.1k-b-PEG_5k (M_n = 6.1 kD, PDI = 1.02), have been synthesized via coupling reactions. The volume fractions of oligomeric cellulose in Cell1.1k-b-PEG1.7k and Cell_1.1k-b-PEG_5k diblock copolymers are 0.32 and 0.14, respectively. Due to the incompatibility between the cellulose and PEG, Cell-b-PEG diblock copolymers can separate at a local scale forming cellulose-rich and PEG-rich nano-domains, which further organize into larger scale structures, both in solutions and in the bulk. Small-angle X-ray scattering, atom force microscopy, and electron microscopy show hierarchical structures of Cell-b-PEG from nanometers to microns.