Transparent, High‐Strength, and Shape Memory Hydrogels from Thermo‐Responsive Amino Acid–Derived Vinyl Polymer Networks

Abstract

Herein, the formation of unique shape‐memory hydrogels that are composed of thermo‐responsive amino‐acid‐derived vinyl polymer networks is reported; these are readily prepared by radical copolymerization of N‐acryloyl glycinamide with commercially available cross‐linkers, namely, methylenebis(acrylamide) and poly(ethylene glycol) diacrylate. These hydrogels are transparent (>90% transmittance at 600 nm) and are comprised of 97–70 wt% water. Furthermore, these contain both chemical and physical cross‐linkages that are based on the multiple hydrogen bonds attained via amino acid units; this composition is aimed at generating opposing stimuli‐responsive characters, namely, chemically stable and thermo‐sensitive properties. A cooperative interplay of these two networks enables the hydrogels to exhibit a decent mechanical toughness (breaking strength ≈0.3 MPa and breaking elongation >600%) and a shape fix/memory capability. The temporary shape is easily fixed by cooling at 4 °C after deformation at high temperature, and it instantly recovers its original shape through reheating. Furthermore, a multi‐shape memory effect is achieved by incorporating the pH‐responsive N‐acryloyl alanine unit into the hydrogel system as a comonomer; in this system, three distinct shapes can be fixed through temperature and pH manipulations. This facilely attainable shape memory hydrogel has significant potential in various fields, such as soft actuators, sensors, and biomedical materials.

Side‐chain amino‐acid‐based polymers: self‐assembly and bioapplications

“…Therefore, stimuli responsiveness is another essential physiognomy of the side-chain amino-acidbased polymers that makes these polymers unique for drug delivery systems (DDSs). 17 A side-chain amino-acid-containing stimuli-responsive hydrogel was reported by Koga et al 35 The amino-acid-based vinyl polymeric hydrogel was composed of 97-70 wt% water and showed thermoresponsive behaviour. Amino-acid-containing polymers with entrapped water mimic the biological environment, and the stimuli responsiveness as well as antifouling properties make them appropriate candidates for drug delivery vehicles.…”

Smart Shape Memory Polyurethane with Photochromism and Mechanochromism Properties

“…Shape memory polymer (SMP) is an intelligent material that can adjust its state parameters (such as shape, position, and strain) under external stimulation, to return to the preset state and is widely used in aerospace, biomedicine, soft actuators, and other fields. [1][2][3][4][5][6][7][8][9] There are several types of SMP materials, and they can be divided into thermally, electrically, photo, magnetically, and chemically actuated SMPs. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] At present, most SMPs are thermally actuated, and they are heated to a shape memory transition temperature T trans (T trans is the shape memory transition temperature, which is the glass transition temperature or melting transition temperature).…”

Thermal/Near‐Infrared Light Dual‐Responsive Reversible Two‐Way Shape Memory cEVA/2D‐MoO2 Composite for Multifunctional Applications

“…Shape memory polymers (SMPs), as a kind of smart materials, can take on a temporary shape under external force and recover from the temporary shape to the original shape in response to external stimuli [ 1 ] (such as temperature, [ 2–5 ] light, [ 6–8 ] electricity, [ 9 ] magnetism, [ 10 ] and solvents [ 11 ] ). SMPs have become a research hotspot of smart materials in the past decades owing to the potential applications in the fields of biomedical sciences, [ 12,13 ] superhydrophobicity, [ 14 ] actuators, [ 6 ] 3D printing, [ 7 ] flexible electronics, [ 15 ] electromagnetic shielding, [ 16 ] and smart textiles.…”