Due to the inherent sustainability and biodegradability,
developing naturally derived thermoresponsive biopolymers in macromolecular
design and synthesis has garnered growing attention, which undergoes
conformational or phase transitions triggered by temperature variations
through the self-assembly of macromolecules 1. Xylan is the third most
abundant renewable polysaccharide in nature after cellulose and chitin, which
shares the same β-1,4 glycosidic linkage as these polysaccharides, but
consists of a maintenance of xylose chain with side branches 2. Herein,
thermoresponsive and photoreactive polymer of xylan-g-allyl glycidyl ether
(xylan-g-AGE) was synthesized by grafting of AGE to debranched xylan
(D-xylan, a chemically engineered linear polysaccharide of β-1,4-linked
xylose), which can be used as a smart building block to thermoresponsive
polymers. Compared to cellulose, D-xylan possesses a broader conformational
space of glycosidic dihedral angles, which provide a greater conformation
flexibility to spatially coordinate the side chains. The hydrophobic
interactions and reformed H-bonds dominant induced the transformation of
xylan-g-AGE from solvated coil chain to self-assembled mesoglobules in an
aqueous solution upon heating. When xylan-g-AGE is used in photoresins to
fabricate hydrogels with high geometric fidelity via DLP 3D printing,
solvated xylan-g-AGE stiffens the PEG hydrogel stronger, related to higher
crosslink density of available AGE moiety and faster crosslinking rate, while
self-assembled xylan-g-AGE toughens the PEG hydrogel better, attributed to
the strategy of ‘dual chemically independent domains’ that smartly combines
tough domain of PEG and the soft domain of self-assembled xylan-g-AGE. MXene
sheets as a conductive additive were further incorporated in the PEG hydrogel
matrix in DLP printing to showcase the potential application in wearable
strain sensors.