Carbohydrates as Hard Segments for Sustainable Elastomers: Carbohydrates Direct the Self-Assembly and Mechanical Properties of Fully Bio-Based Block Copolymers

Abstract

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.

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

“…Ring-opening polymerization (ROP) of δ-decanolactone was carried out at 40 °C using diphenyl phosphate (DPP) and 1,4-benzenedimethanol (BDM) as the catalyst and initiator, respectively, according to a procedure previously reported by us, to produce poly(δdecanolactone) diol (HO−PDL−OH) as the central soft segment of the target triblock copolymer. 14 the products confirmed the disappearance of the absorption band at approximately 2100 cm −1 attributable to azido groups (Figures S9−14b), and each SEC elution peak appeared in a higher molecular weight region compared to the azidofunctionalized PDL peak, which suggests that each click reaction proceeded quantitatively (Figure 2). Furthermore, the 1.…”

“…Directly combining carbohydrate molecules with synthetic polymers is an effective method for achieving the abovementioned goals; this combination can be achieved mainly through grafting synthetic polymer chains onto polysaccharide main chains, − grafting poly/oligosaccharide chains onto synthetic polymer main chains, , and tethering poly/oligosaccharides to synthetic polymers to form block copolymers (BCPs). − Among these, the approach that creates carbohydrate-based BCPs is particularly attractive because of the microphase-separation and micelle-forming abilities of these polymers, which are useful when designing elastomers, − lithographic materials, − electrical materials, − and drug-delivery nanocarriers. − Carbohydrate-based BCPs remain neglected compared to the other two carbohydrate-containing polymer types because of the difficulties associated with their syntheses. Recent progress in polymer chemistry has witnessed the evolution of strategies for the production of carbohydrate-based BCPs since the pioneering syntheses of carbohydrate-based BCPs were published in 1961. , For example, cellulose- b -polystyrene, dextran- b -polystyrene, and maltoheptaose- b -poly­(ε-caprolactone) have been successfully synthesized by radical polymerization and ring-opening polymerization from the reducing end of the carbohydrate segment. ,− However, such a synthetic strategy is incompatible with ionic polymerization methods.…”

Fabrication of Ultrafine, Highly Ordered Nanostructures Using Carbohydrate-Inorganic Hybrid Block Copolymers

“…To overcome this constraint, the enhancement of χ is required, and indeed, numerous research groups have demonstrated microphase-separation from so-called “high χ /low N ” BCPs, resulting in ordered morphologies with d of less than 10 nm. Thus far, silicon-containing [ 3 , 5 , 6 , 7 , 10 , 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], metal-doped [ 31 , 32 , 33 ], and oligosaccharide-based BCPs [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] have been developed. The high χ /low N BCP strategy is now widely accepted as a standard method for obtaining smaller d , although several novel approaches have emerged recently [ 19 , 34 , 35 , 40 , 49 ,…”

“…Thus far, silicon-containing [ 3 , 5 , 6 , 7 , 10 , 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], metal-doped [ 31 , 32 , 33 ], and oligosaccharide-based BCPs [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] have been developed. The high χ /low N BCP strategy is now widely accepted as a standard method for obtaining smaller d , although several novel approaches have emerged recently [ 19 , 34 , 35 , 40 , 49 , 50 , 51 , 52 , 53 , ...…”

Supramolecular polymer-assisted manipulation of triblock copolymers: understanding the relationships between microphase structures and mechanical properties

“…[1][2][3][4] For example, numerous thermoplastic elastomers with high strength and a tunable modulus have been developed by constructing ABA triblock copolymers wherein B is rubbery and the minority A blocks associate to form hard domains as physical cross-links. [5][6][7] Materials based on this kind of copolymer also have inherent defects in mechanical properties, like creep and hysteresis upon deformation. [8][9][10] Discrete supramolecular interactions such as H-bonding and metal-coordination have been utilized to strengthen the hard domain of copolymers, which represents an effective strategy to modify the mechanical properties of materials.…”