NSRRC Activity Report 2022

Soft Matter 035 multiple aldehyde groups, rendering it a highly efficient crosslinker for chitosan network formation. The addition of nanofiber helps to reinforce the network, rendering the cryogel more durable ( Fig. 3 ). In situ SAXS can be used to monitor the structural changes of shape memory cryogel under the formation process in TLS 23A1 . The initial chitosan–cellulose nanofiber cryogel exhibited a circular pattern ( Fig. 4(a) ). This indicated that the cryogel had no specific orientation in its crystalline domain. When the cryogel was heated to 70°C and deformed to the second permanent shape, shape memory was incorporated into the cryogel. This involved the specific orientation of the nanofibers, which was demonstrated by the rhombus shape of the resulting 2D SAXS pattern ( Fig. 4(b) ). The cryogel retained its second permanent shape until its shape memory was triggered by 37°C water. The cryogel recovered its first permanent shape and preserved its rhombus crystalline orientation. A sharp peak at 10.9° in the wide-angle X-ray scattering profile demonstrated the crystalline changes in the cellulose nanofibers ( Fig. 4(c) ). The cellulose nanofibers were thus critical to the cryogel having shape memory. Fig. 2 : Custom-shaped memory cryogel obtained through 3D printing. [Reproduced from Ref. 4] Fig. 3 : Second-generation shape memory cryogel made from chitosan and cellulose nanofibers. [Reproduced from Ref. 3] Fig. 4 : In situ 2D SAXS pattern for cryogel during shape memory incorporation. (a) Initial cryogel; (b) cryogel in the second permanent shape; (c) cryogel returning to the initial shape. [Reproduced from Ref. 3]