Porous boron nitride nanofibers as effective nanofillers for poly(vinyl alcohol) composite hydrogels with excellent self-healing performances

Boron nitride microfiber reinforced polyacrylic acid hydrogels with excellent self-adhesion, fast pH response, and strain sensitivity

Hydrogels are widely utilized in the sensor field, but their inadequate adhesion presents a significant obstacle. Herein, a new multifunctional BNMFs/PAA composite hydrogel was prepared via the incorporation of one-dimensional porous boron nitride microfibers (BNMFs) and polyacrylic acid (PAA) hydrogels. BNMFs, as a reinforcing filler, play a very important role in enhancing the properties of the composite hydrogels. In particular, the porous micrometer structure plays a unique role in improving the adhesion properties of PAA hydrogels. The steric hindrance and the rich hydroxyl functional groups coming from BNMFs are key factors for the excellent adhesion of the composite hydrogels. The composite hydrogels show strong adhesion to various substrate materials. For iron plates and biological tissues, the adhesion energy can reach 1377 J m-2 and 317 J m-2, respectively. In addition, the developed BNMFs/PAA composite hydrogels exhibit excellent mechanical properties. The fracture strain of the composite hydrogels is increased by 2.4 times compared to pure PAA hydrogels. The hydrogen bonds formed between BNMFs and PAA are conducive to the mechanical properties of the BNMFs/PAA composite hydrogels. Meanwhile, BNMFs as fillers play a role in carrying and dissipating force. Furthermore, the BNMFs/PAA composite hydrogels have excellent strain and pH response characteristics. This is because the crosslinking network of the composite hydrogels becomes loose after the addition of BNMFs, resulting in rapid ion transport pathways. Therefore, the developed BNMFs/PAA composite hydrogels will have broad application prospects in the fields of motion monitoring, intelligent skin and biological adhesives.

High-Strength Magnetic Hydrogels with Photoweldability Made by Stepwise Assembly of Magnetic-Nanoparticle-Integrated Aramid Nanofiber Composites

Hydrogels capable of transforming in response to a magnetic field hold great promise for applications in soft actuators and biomedical robots. However, achieving high mechanical strength and good manufacturability in magnetic hydrogels remains challenging. Here, inspired by natural load-bearing soft tissues, a class of composite magnetic hydrogels is developed with tissue-mimetic mechanical properties and photothermal welding/healing capability. In these hydrogels, a hybrid network involving aramid nanofibers, Fe₃O₄ nanoparticles, and poly(vinyl alcohol) is accomplished by a stepwise assembly of the functional components. The engineered interactions between nanoscale constituents enable facile materials processing and confer a combination of excellent mechanical properties, magnetism, water content, and porosity. Furthermore, the photothermal property of Fe₃O₄ nanoparticles organized around the nanofiber network allows near-infrared welding of the hydrogels, providing a versatile means to fabricate heterogeneous structures with custom designs. Complex modes of magnetic actuation are made possible with the manufactured heterogeneous hydrogel structures, suggesting opportunities for further applications in implantable soft robots, drug delivery systems, human-machine interactions, and other technologies.

Porous boron nitride nanofibers enhanced sodium acrylate and acrylamide copolymer hydrogels for effective adsorption of Pb2

A new composite hydrogel adsorbent for adsorption of Pb²⁺ has been prepared by combining porous boron nitride nanofibers (BNNFs) and the acrylamide and sodium acrylate copolymer (P(AANa-co-AM)) via a chemical crosslinking method. Porous BNNFs with abundant hydroxyl functional groups can form hydrogen bond interactions with carboxyl and amino functional groups of the copolymer in the composite hydrogel and carry and dissipate forces for the composite hydrogels. So the mechanical performances of the copolymer hydrogels can be effectively improved, which is very valuable for the practical application of the composite hydrogel to remove Pb²⁺ from waste water. The thermal stability and swelling performance of the pure copolymer hydrogels were also greatly improved. This is not only because of the strong hydrogen bond interactions but also the good thermal stability and flexibility of BNNFs. The composite hydrogel adsorbent shows superior adsorption capacity for Pb²⁺ (490.2 mg g^-1) to most of the reported hydrogel adsorbents. The chemisorption dominates the whole adsorption process according to the pseudo-second-order kinetic and the Langmuir models. The composite hydrogel adsorbent also shows good reusability. Therefore, we believe that the prepared composite hydrogels will play an important role in removing Pb²⁺ from wastewater.