Non-covalent interaction cooperatively induced stretchy, tough and stimuli-responsive polyurethane–urea supramolecular (PUUS) hydrogels

Abstract

to now, fabrication of strong and stimuli-responsive supramolecular hydrogels via easy molecular design and synthesis procedure is still a big challenge. In this work, a series of hydrophobicly modified linear polyurethane-urea copolymers and one polyurethane copolymer were prepared via a greatly simplified one-pot approach to investigate the synergistic effect between hydrogen -bonding and hydrophobic effect. FT-IR and various mechanical performance studies show that not only longer hydrophobic spacer (C12) but also stronger hydrogen-bonding unit (urea) are necessary for their synergistic effect to yield high water containing, transparent, stretchy and tough supramolecular hydrogels. Moreover, these supramolecular materials also show nice cyclic shape-memory behaviours which can be realized under mild conditions, e.g. in air and water at room temperature. The noncovalent interaction's synergistic effect and stimuli-responsive character are expected to dramatically expand the design and choice of tough and smart supramolecular hydrogels/materials for biomaterials.

Controllable Hierarchical Surface Patterns of Supramolecular Hydrogels: Harnessing Buckling Instability by Confinement

“…[34,35] Large-area and highly ordered hydrogel nanostripes were fabricated by the nanoimprint lithography system (Entire 3, Obducat). [34,35] Large-area and highly ordered hydrogel nanostripes were fabricated by the nanoimprint lithography system (Entire 3, Obducat).…”

“…Beyond ac riticald egree of swelling (ca. [34,35] The supramolecular hydrogel was firstly patterned into arrays of nanostripesb yn anoembossing techniques. [27][28][29][30] Althought heoretical and experimental studies on the formation of buckling patterns on different geometries, such as stripes, disks, tubes, spheres bound to ah ard substrate, and freestanding porous films have been reported, [28,31] taking advantage of bucklingh ydrogel films has been rarely extended to create hierarchical patternsw ith long-range orders.…”

“…2), [26] the surfaceb ecomes mechanically unstable, resulting in spontaneous disordered patterns such as folds andc reases through bucklinginstability without the need for externalloads. [34,35] The procedure for fabricating arrays of nanostripes in the PEG-based PUU supramolecular hydrogelt hin films is illustrated in Figure 1. [32,33] Herein, we report on the controllable and long-range ordered hierarchical surface patterns in hydrogel thin films by combining nanoembossing methodology with intrinsic buckling instability.Apoly(ethylene glycol)( PEG)-based polyurethane-urea (PUU) supramolecular hydrogel is selected as the model compound as it shows excellent solution processability,h igh mechanical strengtha nd fast stimuli responsiveness through self-complementary PUU units encapsulated within hydrophobic domains.…”

“…When the potentiale nergy V becomes negative, the hydrogel films are unstable, leadingt or andomlyd istributed cusp patterns on the free surface with acharacteristic wavelength l of [27] l ¼ 2p where E 2 is the elasticm odulus of underlying bulk of the hydrogel. [34] In contrast to homogeneous films, the swelling can occur vertically and laterallyi nt he direction normal to the nanostripes, generating an axial compressives tress along the nanostripes. [34] In contrast to homogeneous films, the swelling can occur vertically and laterallyi nt he direction normal to the nanostripes, generating an axial compressives tress along the nanostripes.…”

“…[32,33] Herein, we report on the controllable and long-range ordered hierarchical surface patterns in hydrogel thin films by combining nanoembossing methodology with intrinsic buckling instability.Apoly(ethylene glycol)( PEG)-based polyurethane-urea (PUU) supramolecular hydrogel is selected as the model compound as it shows excellent solution processability,h igh mechanical strengtha nd fast stimuli responsiveness through self-complementary PUU units encapsulated within hydrophobic domains. [34,35] The supramolecular hydrogel was firstly patterned into arrays of nanostripesb yn anoembossing techniques. Upon immersion into water,t he bucklingi nstability thuss electively occurs on the free surfaces of nanostripes.…”