Synthesis and Self-assembly of Saccharide-Polystyrene Hybrid Block Copolymers

Oligosaccharide based block copolymers are a new class of hybrid polymers containing both natural and synthetic segments. Due to the large segregation strength between the hydrophilic saccharide block and the hydrophobic synthetic block, the resulting block copolymers are expected to microphase separate at small molecular weights, yielding ordered morphologies with sub-10nm feature sizes. In this contribution, a series of saccharide-containing diblocks and triblocks were prepared by combining maltotriose with polystyrene of different chain lengths. The polymer conjugates were synthesized via copper(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition of alkyne-functionalized maltotriose and azido-functionalized polystyrene. Additionally, bifunctional initiators were used to prepare triblocks of polystyrene center block and maltotriose end blocks. Despite the small size of maltotriose, the resulting block copolymers were found to microphase separate to form well-ordered microdomain structures. Their bulk morphologies as well as order-disorder transition behavior were examined to illustrate the complex phase behavior of these hybrid materials.