Fabrication of Shape‐Memory Aerogel Based on Chitosan/Poly(ethylene glycol) Diacrylate Semi‐Interpenetrating Networks via a Facile and Eco‐Friendly Strategy

Abstract

exhibit strong advantages in providing diverse mechanical properties, such as varying from stiff to high elasticity to enable adaption to a wide range of demands.While the application of aerogels in smart materials has attracted increasing attention, ensuring full functionality in a porous structure is still highly challenging. As one of the booming smart materials, shape-memory polymers (SMPs) have been intensively investigated, and numerous multiresponsive, [20][21][22][23][24][25] multifunctional shape memory polymeric bulk materials [26][27][28][29] or hydrogels [30][31][32][33][34][35] have been developed. However, to the best of our knowledge, there have been very few reports about shape memory aerogels. [36,37] Rowan and coworkers [38] developed a thermal responsive shape memory aerogel from a thiol-ene network with a glass temperature above room temperature, and showed that it displays very good shape memory performance. However, this shape memory aerogel is produced from an organogel. Generally, fabricating aerogels from hydrogels is a more economical and eco-friendly strategy.Herein, we seek to develop a shape memory polymeric aerogel (SMPA) from the corresponding hydrogel via an eco-friendly strategy by choosing water soluble and highly matchable constituent materials. It is well-known that crystalline poly(ethylene glycol) (PEG) with a melting temperature (T m ) above room temperature is a favorable component for the development of thermally induced SMPs, and its water solubility makes it a good candidate for SMPA. However, the aerogel formed from a single highly crystalline PEG component will show a poor mechanical performance. To address this problem, we considered chitosan (CS) which is a biobased material derived from sustainable resources. CS is obtained by deacetylation of chitin and its physicochemical properties are determined by the degree of deacetylation and molecular weight. [39] It was identified as a good start material for fabricating aerogels with unique advantages, such as good flexibility, nontoxicity, cost-effectiveness and biodegradability. Thus, CS was chosen as the other precursor material to enhance the aerogel skeleton. In this work, we prepared a shape memory aerogel based on chitosan/poly(ethylene glycol) diacrylate (CS/PEGDA) semi-interpenetrating networks (semi-IPNs) via a facile one-pot photocrosslinking approach. The feed ratio of CS and diacrylic PEG (PEGDA) precursors with different molecular weights were tuned to Shape-Memory Aerogels While the field of shape memory polymers (SMPs) has developed rapidly, it is still highly challenging to obtain SMPs in the form of aerogels (SMPAs) due to the unique technique used for the fabrication of the aerogels and their high porosity. Herein, a thermally induced SMPA based on chitosan/poly(ethylene glycol) diacrylate (CS/PEGDA) semi-interpenetrating networks is reported that are produced using an eco-friendly strategy. The main network is responsible for the shape memory effect (SME) and can be easily tuned by varying the feed rat...

A Liquid Crystal Elastomer‐Based Unprecedented Two‐Way Shape‐Memory Aerogel

“…Since Rowan reported the first thermal-responsive SMPA material with the capabilities of shape fixation and shape recovery in 2016, [8] many research groups have focused on this field and reported a series of novel SMPAs originating from traditional shape memory polymeric materials. [9][10][11][12] A significant commonality of these previous reported SMPA materials is that they can only perform a one-way shape-memory deformation. As shown in Figure 1a, the one-way SMPAs (1W-SMPA, permanent shape 1) were first deformed at a relatively high temperature (usually higher than their glass transition or melting temperatures) and then cooled back to room temperature to obtain a temporary shape (temporary shape 2).…”

“…Since Rowan reported the first thermal‐responsive SMPA material with the capabilities of shape fixation and shape recovery in 2016, [ 8 ] many research groups have focused on this field and reported a series of novel SMPAs originating from traditional shape memory polymeric materials. [ 9 , 10 , 11 , 12 ]…”

Anisotropic conductive shape-memory aerogels as adaptive reprogrammable wearable electronics for accurate long-term pressure sensing

“…22–24 In addition, the fabrication of aerogels is feasible because the internal pores can be easily tuned by adjusting the concentration of precursors as well as freeze-drying parameters, such as temperature, pressure, and even the freeze direction. 25–27 However, current aerogels always lack shape-shifting capacity. 28,29 Shape-memory polymers are emerging nature-inspired stimuli-responsive materials with the capacity to recover to their original geometry from an arbitrary temporary shape generated by elaborately programming upon a certain external stimulus, such as heat, light, and chemicals, and of course, the so-called shape-memory effect.…”

Synthesis and Properties of a New Chitosan‐Based Shape Memory Polymer and its Composites

“…[24] A thermally induced SMP aerogel based on CH/poly (ethylene glycol) diacrylate has been produced using an eco-friendly strategy wherein the interpenetrated CH acts as the main network to enhance the aerogel skeleton. [25] Remote and contactless controllability of shape recovery kinetics has been demon-strated for CH/rGO strips cross-linked with ethylene glycol diglycidyl ether at pH 10.5 by changing the light intensities. [26] From the above references, it is evident that mostly CH has been added as a filler or used for modifying the surfaces.…”

“…A polycaprolactone based toughened shape memory polyurethane biocomposite exhibited an ultimate tensile strength of 5.2 MPa, and its composite containing 10 % nano CH flakes showed an ultimate tensile strength of 12 MPa [24] . A thermally induced SMP aerogel based on CH/poly (ethylene glycol) diacrylate has been produced using an eco‐friendly strategy wherein the interpenetrated CH acts as the main network to enhance the aerogel skeleton [25] . Remote and contactless controllability of shape recovery kinetics has been demonstrated for CH/rGO strips cross‐linked with ethylene glycol diglycidyl ether at pH 10.5 by changing the light intensities [26] …”