Synthesis and Self-assembly of Saccharide-Containing Triblock Copolymers

Hybrid block copolymers containing both oligosaccharide and synthetic polymer components have attracted much interest as sustainable material alternatives. In particular block copolymers containing small saccharide units such as mono-, di-, and tri-saccharides are capable of microphase separation to form regular domain morphologies despite their small molecular weights. In this contribute, we report the synthesis and morphology characterization of ABA-type triblock copolymers containing polystyrene (PS) as the synthetic mid-block and different saccharide molecules as end blocks. The triblocks were synthesized via copper(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition of alkyne-functionalized saccharides and difunctional azido-PS. The polymer bulk morphologies were then examined by a combination of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For triblocks containing maltotriose, they were found to self-assemble to form well-ordered sphere and cylinder morphologies with sub-10nm domain periodicity. For triblocks containing even smaller maltose units as the end blocks, microphase separation was also confirmed. However, the long-range order of the microdomains was compromised due to the low degradation temperature of the saccharide blocks.