A nanocomposite interpenetrating hydrogel with high toughness: effects of the posttreatment and molecular weight
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ORIGINAL CONTRIBUTION
A nanocomposite interpenetrating hydrogel with high toughness: effects of the posttreatment and molecular weight Chao Niu 1 & Huijuan Zhang 1 & Biao Yang 1 Received: 23 January 2020 / Revised: 4 September 2020 / Accepted: 27 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Previously, we prepared a tough nanocomposite interpenetrating hydrogel by chemical crosslinking of acrylamide (AM) with vinyl-modified silica nanoparticles (VSNPs), combined with physical crosslinking of polyvinyl alcohol (PVA). It is well-known that posttreatment method and molecular weight play important roles in the mechanical properties of the tough hydrogels. In this paper, different post-treatment methods, i.e., freeze-thaw and annealing-swelling and varying PVA degree of polymerization (500 and 1700) were used to prepare the nanocomposite interpenetrating hydrogels. The effects of posttreatment and PVA molecular weight on the mechanical and swelling properties were investigated in detail. Tensile tests showed that annealingswelling process exerted a more pronounced influence on elevating the tensile strength of nanocomposite interpenetrating hydrogels, which arose from the increased crystallization degree of PVA and the denser network. Hydrogels with lower PVA molecular weight have higher tensile strength after freeze-thaw cycle than that with higher PVA molecular weight. Cyclic loading–unloading tests revealed that the gels with lower molecular weight of PVA can dissipate higher energy at 100% strain. The swelling kinetic study revealed that the swelling behaviors of nanocomposite interpenetrating hydrogels followed the pseudo-second-order dynamic equation. Keywords Hydrogels . Nanocomposites . Swelling behavior
Introduction Hydrogels have drawn much attention and interest due to their unique properties, and have been used in drug delivery [1–3], tissue engineering [4–6], sensors [7–9], and so on. Traditional hydrogels suffer from lower strength and toughness, and their potential applications as mechanic device have been limited to a large extent. To overcome this shortcoming, a large amount of mechanically strong gels have been developed, including topological (TP) hydrogels [10–14], nanocomposite (NC) hydrogels [15–18], and double network (DN) hydrogels [19–23]. The reinforcement of these tough hydrogels is usually realized by modulating the inherent characteristic of polymer matrixes, crosslinking manners, or preparation methods. Polyvinyl alcohol (PVA) is one of the nontoxic, environmentally friendly, biodegradable, and water-soluble polymers * Huijuan Zhang [email protected] 1
School of Material and Mechanical Engineering, Beijing Technology and Business University, Beijing 100048, China
[24]. PVA-based double-network hydrogels have been extensively applied for various fields [25, 26]. The vast number of hydroxyl side groups in PVA not only makes it hydrophilic but also allows this polymer to form a semicrystalline structure through intramolecular hydrogen bonding
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