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ACS Appl Mater Interfaces ; 13(19): 22774-22784, 2021 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-33944548


Polyacrylamide is widely employed in constructing functional hydrogels. However, the volume expansion of this hydrogel in water weakens its mechanical properties and restricts its application. Herein, we report a strategy to convert the swollen and weak polyacrylamide/carboxymethyl chitosan hydrogel into a strong and tough one by hydrolysis in acid solution with an elevated temperature. The obtained hydrolyzed hydrogels possess a high strength, toughness, and tearing fracture energy of 5.9 MPa, 22 MJ/m3 and 7517 J/m2, which are 254, 535 and 186 times higher than those of the original swollen one, respectively. In addition, the gels demonstrate low residual strain and rapid self-recovery abilities. Moreover, the gels have good shape memory behavior controlled by temperature. Furthermore, the gels can be worked as strain sensors with a broad strain window, high sensitivity, excellent linear response, and great durability in monitoring human motions after immersing treatment in a normal saline solution. This work provides a new method for preparing the stretchable and tough polyacrylamide-based hydrogels used in the areas of soft actuators and flexible electronics.

J Colloid Interface Sci ; 594: 54-63, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-33756368


Organic dye-containing wastewater has become an increasingly serious environmental problem due to the rapid development of the printing and dyeing industry. Hydrogel is a promising adsorbent for organic dyes because of its unique three-dimension network structure and versatile functional groups. Though many efforts have been made in hydrogel adsorbents recently, there is still a critical challenge to fabricate hydrogel adsorbent with high adsorption capacity and high efficiency at the same time. To address this concern, we developed a calcium hydroxide nano-spherulites/poly(acrylic acid -[2-(Methacryloxy)ethyl]trimethyl ammonium chloride) hydrogel adsorbent with novel villi-like structure. The hydrogels were prepared through a simple free radical copolymerization method using calcium hydroxide nano-spherulites as crosslinker. The resultant hydrogel adsorbents showed a maximum adsorption capacity of 2249 mg/g in a 400 mg/L methylene blue solution and a high removal ratio of 98% in 1 h for a 50 mg/L methylene blue solution. In addition, the adsorption behaviors of our hydrogel adsorbents could be well described by pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Furthermore, this kind of hydrogel adsorbent showed selective adsorption behavior for methylene blue. Altogether, the hydrogel adsorbent developed in this work has a high capacity and high efficiency in organic dye removing and promised a great potential in wastewater treatment application.

ACS Appl Mater Interfaces ; 13(6): 7443-7452, 2021 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-33528998


Flexible electronics greatly facilitate human life due to their convenience and comfortable utilization. Liquid metals are an ideal candidate for flexible devices; however, the high surface tension and poor surface wettability restrict their application on diverse substrates. Herein, a printable and recyclable ink composed of poly(vinyl alcohol) and a liquid metal (PVA-LM) was developed to resolve these problems. The materials were designed considering the compatibility between PVA and the liquid metal, and the composite theory was applied to determine the component proportion. The developed composites improved the surface wettability of the liquid metal on diverse substrates, and three-dimensional (3D) printing technology was chosen to maximize the use of this material. Moreover, the PVA-LM ink showed excellent conductivity of about 1.3 × 105 S/m after being turned on, which favored the designing of alarm systems and object locators. The flexible sensors produced with this ink have broad application, high sensitivity, and superstable signal generation even after 200 cycles. When acting as strain sensors, the constructed composites had high sensitivity for monitoring the human movements. Furthermore, liquid metals in printed products can be recycled under alkaline conditions. This study opens a new direction for the next generation of environmentally friendly flexible devices.

Carbohydr Polym ; 248: 116797, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32919535


There is a growing demand for hydrogel-based sensors due to their biomimetic structures and properties, as well as biocompatibility. However, it is still a challenge to fabricate hydrogel sensor with integration of good mechanical properties and high conductivity. Herein, a tough and conductive hydrogel is developed with semi-interpenetrating network formed by incorporating carboxymethyl chitosan and sodium chloride into polyacrylamide network. The hydrogels have high tensile strength, elongation and toughness, but low modulus comparable to human skin. In addition, the hydrogels exhibit fast self-recovery and satisfactory self-healing capabilities. Owing to the existence of sodium chloride, the hydrogel also has high conductivity, good water retention property and anti-freezing ability. When used as a strain sensor, it demonstrates a broad strain window and shows a high sensitivity in monitoring human motions. This work provides a facile method in fabricating multifunctional ionic conductive hydrogel for applications in wearable electronics and soft robotics.