Smart H₂O₂‑Responsive Drug Delivery System Made by Halloysite Nanotubes and Carbohydrate Polymers

A novel chemical hydrogel was facilely achieved by coupling 1,4-phenylenebisdiboronic acid modified halloysite nanotubes (HNTs-BO) with compressible starch. The modified halloysite nanotubes (HNTs) and prepared hydrogel were characterized by solid-state nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The linkage of B–C in the hydrogel can be degraded into B–OH and C–OH units in the presence of H₂O₂ and result in the degradation of the chemical hydrogel. Pentoxifylline was loaded into the lumen of the HNTs-BO, and then gave the pentoxifylline-loaded hydrogel. The drug release profile shows that it was no more than 7% dissolved when using phosphate buffer solution (PBS) as the release medium. Notably, a complete release (near 90%) can be achieved with the addition of H₂O₂ ([H₂O₂] = 1 × 10^–4 M), suggesting a high H₂O₂ responsiveness of the as-formed hydrogel. The drug release results also show that the “initial burst release” can be effectively suppressed by loading pentoxifylline inside the lumen of the HNTs rather than embedding the drug in the hydrogel network. The drug-loaded hydrogel with H₂O₂-responsive release behavior may open up a broader application in the field of biomedicine

Strain-Induced Phase Separation and Mechanomodulation of Ionic Conduction in Anisotropic Nanocomposite Ionogels

Ionogels have great potential for the development of tissue-like, soft, and stretchable ionotronics. However, conventional isotropic ionogels suffer from poor mechanical properties, low efficient force transmission, and tardy mechanoelectric response, hindering their practical utility. Here, we propose a simple one-step method to fabricate bioinspired anisotropic nanocomposite ionogels based on a combination of strain-induced phase separation and mechanomodulation of ionic conduction in the presence of attapulgite nanorods. These ionogels show high stretchability (747.1% strain), tensile strength (6.42 MPa), Young’s modulus (83.49 MPa), and toughness (18.08 MJ/m3). Importantly, the liquid crystalline domain alignment-induced microphase separation and ionic conductivity enhancement during stretching endow these ionogels with an unusual mechanoelectric response and dual-programmable shape-memory properties. Moreover, the anisotropic structure, good elasticity, and unique resistance–strain responsiveness give the ionogel-based strain sensors high sensitivity, rapid response time, excellent fatigue resistance, and unique waveform-discernible strain sensing, which can be applied to real-time monitoring of human motions. The findings offer a promising way to develop bioinspired anisotropic ionogels to modulate the microstructure and properties for practical applications in advanced ionotronics

Strain-Induced Phase Separation and Mechanomodulation of Ionic Conduction in Anisotropic Nanocomposite Ionogels

Ionogels have great potential for the development of tissue-like, soft, and stretchable ionotronics. However, conventional isotropic ionogels suffer from poor mechanical properties, low efficient force transmission, and tardy mechanoelectric response, hindering their practical utility. Here, we propose a simple one-step method to fabricate bioinspired anisotropic nanocomposite ionogels based on a combination of strain-induced phase separation and mechanomodulation of ionic conduction in the presence of attapulgite nanorods. These ionogels show high stretchability (747.1% strain), tensile strength (6.42 MPa), Young’s modulus (83.49 MPa), and toughness (18.08 MJ/m3). Importantly, the liquid crystalline domain alignment-induced microphase separation and ionic conductivity enhancement during stretching endow these ionogels with an unusual mechanoelectric response and dual-programmable shape-memory properties. Moreover, the anisotropic structure, good elasticity, and unique resistance–strain responsiveness give the ionogel-based strain sensors high sensitivity, rapid response time, excellent fatigue resistance, and unique waveform-discernible strain sensing, which can be applied to real-time monitoring of human motions. The findings offer a promising way to develop bioinspired anisotropic ionogels to modulate the microstructure and properties for practical applications in advanced ionotronics

Strain-Induced Phase Separation and Mechanomodulation of Ionic Conduction in Anisotropic Nanocomposite Ionogels

Ionogels have great potential for the development of tissue-like, soft, and stretchable ionotronics. However, conventional isotropic ionogels suffer from poor mechanical properties, low efficient force transmission, and tardy mechanoelectric response, hindering their practical utility. Here, we propose a simple one-step method to fabricate bioinspired anisotropic nanocomposite ionogels based on a combination of strain-induced phase separation and mechanomodulation of ionic conduction in the presence of attapulgite nanorods. These ionogels show high stretchability (747.1% strain), tensile strength (6.42 MPa), Young’s modulus (83.49 MPa), and toughness (18.08 MJ/m3). Importantly, the liquid crystalline domain alignment-induced microphase separation and ionic conductivity enhancement during stretching endow these ionogels with an unusual mechanoelectric response and dual-programmable shape-memory properties. Moreover, the anisotropic structure, good elasticity, and unique resistance–strain responsiveness give the ionogel-based strain sensors high sensitivity, rapid response time, excellent fatigue resistance, and unique waveform-discernible strain sensing, which can be applied to real-time monitoring of human motions. The findings offer a promising way to develop bioinspired anisotropic ionogels to modulate the microstructure and properties for practical applications in advanced ionotronics

Strain-Induced Phase Separation and Mechanomodulation of Ionic Conduction in Anisotropic Nanocomposite Ionogels

Ionogels have great potential for the development of tissue-like, soft, and stretchable ionotronics. However, conventional isotropic ionogels suffer from poor mechanical properties, low efficient force transmission, and tardy mechanoelectric response, hindering their practical utility. Here, we propose a simple one-step method to fabricate bioinspired anisotropic nanocomposite ionogels based on a combination of strain-induced phase separation and mechanomodulation of ionic conduction in the presence of attapulgite nanorods. These ionogels show high stretchability (747.1% strain), tensile strength (6.42 MPa), Young’s modulus (83.49 MPa), and toughness (18.08 MJ/m3). Importantly, the liquid crystalline domain alignment-induced microphase separation and ionic conductivity enhancement during stretching endow these ionogels with an unusual mechanoelectric response and dual-programmable shape-memory properties. Moreover, the anisotropic structure, good elasticity, and unique resistance–strain responsiveness give the ionogel-based strain sensors high sensitivity, rapid response time, excellent fatigue resistance, and unique waveform-discernible strain sensing, which can be applied to real-time monitoring of human motions. The findings offer a promising way to develop bioinspired anisotropic ionogels to modulate the microstructure and properties for practical applications in advanced ionotronics

Strain Hardening Behavior of Poly(vinyl alcohol)/Borate Hydrogels

The large-amplitude oscillatory shear (LAOS) behavior of poly­(vinyl alcohol) (PVA)/borate hydrogels was investigated with the change of scanning frequency (ω) as well as concentrations of borate and PVA. The different types (Types I–IV) of LAOS behavior are successfully classified by the mean number of elastically active subchains per PVA chain (<i>f</i>_eas) and Deborah number (<i>D</i>_e = ωτ, τ is the relaxation time of sample). For the samples with Type I behavior (both storage modulus <i>G</i>′ and loss modulus <i>G</i>″ increase with strain amplitude γ, i.e., intercycle strain hardening), the critical value of strain amplitude (γ_crit) at the onset of intercycle strain hardening is almost the same when <i>D</i>_e > ∼2 (Region 3), while the value of Weissenberg number (<i>Wi</i> = γ<i>D</i>_e) at γ_crit is similar when <i>D</i>_e < ∼0.2 (Region 1). For intracycle behavior in the Lissajous curve, intracycle strain hardening is only observed in viscous Lissajous curve of Region 1 or in the elastic Lissajous curve of Region 3. In Region 1, both intercycle and intracycle strain hardening are mainly caused by the strain rate-induced increase in the number of elastically active chains, while non-Gaussian stretching of polymer chains starts to contribute as <i>Wi</i> > 1. In Region 3, strain-induced non-Gaussian stretching of polymer chains results in both intercycle and intracycle strain hardening. In Region 2 (∼0.2 < <i>D</i>_e < ∼2), two involved mechanisms both contribute to intercycle strain hardening. Furthermore, by analyzing the influence of characteristic value of <i>D</i>_e as 1 on the rheological behavior of PVA/borate hydrogels, it is concluded that intercycle strain hardening is dominated by strain-rate-induced increase in the number of elastically active chains when <i>D</i>_e < 1, while strain-induced non-Gaussian stretching dominates when <i>D</i>_e > 1

Dependences of Rheological and Compression Mechanical Properties on Cellular Structures for Impact-Protective Materials

In this study, three typical impact-protective materials, D3O, PORON XRD, and DEFLEXION were chosen to explore the dependences of rheological and compression mechanical properties on the internal cellular structures with polymer matrix characteristics, which were examined using Fourier transform infrared spectroscopy, thermogravimetric analyses, and scanning electron microscopy with energy dispersive spectroscopy. The rheological property of these three foaming materials were examined using a rheometer, and the mechanical property in a compression mode was further examined using an Instron universal tensile testing machine. The dependences of rheological parameters, such as dynamic moduli, normalized moduli, and loss tangent, on angular frequency, and the dependences of mechanical properties in compression, such as the degree of strain-hardening, hysteresis, and elastic recovery, on the strain rate for D3O, PORON XRD, and DEFLEXION can be well-correlated with their internal cellular structural parameters, revealing, for example, that D3O and PORON XRD exhibit simultaneously high strength and great energy loss in a high-frequency impact, making them suitable for use as soft, close-fitting materials; however, DEFLEXION dissipates much energy whether it suffers a large strain rate or not, making it suitable for use as a high-risk impact-protective material. The rheometry and compression tests used in this study can provide the basic references for selecting and characterizing certain impact-protective materials for applications

Strain-Induced Phase Separation and Mechanomodulation of Ionic Conduction in Anisotropic Nanocomposite Ionogels

Ionogels have great potential for the development of tissue-like, soft, and stretchable ionotronics. However, conventional isotropic ionogels suffer from poor mechanical properties, low efficient force transmission, and tardy mechanoelectric response, hindering their practical utility. Here, we propose a simple one-step method to fabricate bioinspired anisotropic nanocomposite ionogels based on a combination of strain-induced phase separation and mechanomodulation of ionic conduction in the presence of attapulgite nanorods. These ionogels show high stretchability (747.1% strain), tensile strength (6.42 MPa), Young’s modulus (83.49 MPa), and toughness (18.08 MJ/m3). Importantly, the liquid crystalline domain alignment-induced microphase separation and ionic conductivity enhancement during stretching endow these ionogels with an unusual mechanoelectric response and dual-programmable shape-memory properties. Moreover, the anisotropic structure, good elasticity, and unique resistance–strain responsiveness give the ionogel-based strain sensors high sensitivity, rapid response time, excellent fatigue resistance, and unique waveform-discernible strain sensing, which can be applied to real-time monitoring of human motions. The findings offer a promising way to develop bioinspired anisotropic ionogels to modulate the microstructure and properties for practical applications in advanced ionotronics

Liquid Crystalline Phase Behavior and Sol–Gel Transition in Aqueous Halloysite Nanotube Dispersions

The liquid crystalline phase behavior and sol–gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol–gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects

Strain Hardening Behavior of Poly(vinyl alcohol)/Borate Hydrogels

The large-amplitude oscillatory shear (LAOS) behavior of poly­(vinyl alcohol) (PVA)/borate hydrogels was investigated with the change of scanning frequency (ω) as well as concentrations of borate and PVA. The different types (Types I–IV) of LAOS behavior are successfully classified by the mean number of elastically active subchains per PVA chain (<i>f</i>_eas) and Deborah number (<i>D</i>_e = ωτ, τ is the relaxation time of sample). For the samples with Type I behavior (both storage modulus <i>G</i>′ and loss modulus <i>G</i>″ increase with strain amplitude γ, i.e., intercycle strain hardening), the critical value of strain amplitude (γ_crit) at the onset of intercycle strain hardening is almost the same when <i>D</i>_e > ∼2 (Region 3), while the value of Weissenberg number (<i>Wi</i> = γ<i>D</i>_e) at γ_crit is similar when <i>D</i>_e < ∼0.2 (Region 1). For intracycle behavior in the Lissajous curve, intracycle strain hardening is only observed in viscous Lissajous curve of Region 1 or in the elastic Lissajous curve of Region 3. In Region 1, both intercycle and intracycle strain hardening are mainly caused by the strain rate-induced increase in the number of elastically active chains, while non-Gaussian stretching of polymer chains starts to contribute as <i>Wi</i> > 1. In Region 3, strain-induced non-Gaussian stretching of polymer chains results in both intercycle and intracycle strain hardening. In Region 2 (∼0.2 < <i>D</i>_e < ∼2), two involved mechanisms both contribute to intercycle strain hardening. Furthermore, by analyzing the influence of characteristic value of <i>D</i>_e as 1 on the rheological behavior of PVA/borate hydrogels, it is concluded that intercycle strain hardening is dominated by strain-rate-induced increase in the number of elastically active chains when <i>D</i>_e < 1, while strain-induced non-Gaussian stretching dominates when <i>D</i>_e > 1