A series of fully bio-based block copolymers (BCPs) consisting of maltooligosaccharides (maltose, maltotriose, maltotetraose, and maltohexaose; A block) and poly(δ-decanolactone) (PDL; B block), with ABA-, A2BA2-, A3BA3-, A(BA)2-, and A2(BA)2-type architectures, were synthesized to demonstrate the potential of oligosaccharides as novel hard segments for biobased elastomers. To understand the correlation between the BCP molecular structure and material properties, the BCPs were designed to have comparable molecular weights (ca. 12k) and total numbers of glucose units (12). Morphological analysis revealed the formation of bodycentered cubic sphere and hexagonally close-packed cylinder (HEX) morphologies depending on the branched architecture (interdomain distance 9.7-14.4 nm). While the PDL homopolymer is a viscous liquid due to its low Tg and amorphous nature, all BCPs exhibited elastomeric properties, confirming that the oligosaccharide blocks segregated to form the hard domains to crosslink the rubbery PDL chains. Tensile testing revealed that the mechanical properties of the BCPs were mainly determined by the microphase-separated structure and less affected by the length of each oligosaccharide chain. The HEX-forming A2BA2and A3BA3-type BCPs exhibited Young's moduli of ~6 MPa, which is comparable to well-known styrene-based thermoplastic elastomers. Furthermore, a readily available polydisperse maltooligosaccharide was employed to synthesize an A2BA2-type BCP with a higher molecular weight PDL block (20k), which exhibited a Young's modulus of ~6 MPa and an elongation at break of ~700%. These results demonstrate that oligosaccharides are a sustainable alternative to the petroleum-derived synthetic hard segments (e.g., polystyrene), thereby opening up a new avenue for fully bio-based soft material design.

We synthesized a series of new intrinsically stretchable block copolymers (BCPs) in linear AB-type, ABA-type, and star-shaped architectures composed of oligosaccharide (MH) and flexible poly­(n-butyl acrylate) (PBA) blocks for the application in field-effect transistor memory. The BCP thin films are used as the charge trapping layers in the memory devices where the BCPs phase separate into ordered MH microdomains in soft PBA matrices. The MH microdomain works as the charge-trapping sites while the soft PBA matrix provides a stretchability. In particular, the BCPs of the ABA-type and star-shaped architectures with the end MH blocks not only show superior memory performances but also form physical networks that impart mechanical resilience to the thin films such that they can endure 100% strain without formation of cracks. The mobilities and the memory windows of the devices are nearly constant even when the charge trapping layers are stretched and released at 50% strain for 1000 cycles. This work highlights the importance of the molecular architectures on the BCPs intended for stretchable electronic materials.

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