Biodegradable Poly(acrylic acid-co-acrylamide)/Poly(vinyl alcohol) Double Network Hydrogels with Tunable Mechanics and High Self-healing Performance

Abstract

We proposed a novel strategy in the fabrication of biodegradable poly(acrylic acid-co-acrylamide)/poly(vinyl alcohol) (P(AAc-co-Am)/PVA) double network (DN) hydrogels with good mechanical and self-healing properties. In the DN hydrogel system, P(AAc-co-Am) polymers form a network through the ionic coordinates between –COO– and Fe3+ and hydrogen bonding between –COOH and –CONH2, while another network is fabricated by the complexation between PVA and borax. The influences of the composition on the rheological behaviors and mechanical properties of the synthesized DN hydrogels were investigated. The rheological measurements revealed that the viscoelasticity and stiffness of the P(AAc-co-Am)/PVA DN hydrogels increase as the acrylamide and Fe3+ concentrations increase. At 0.05 mmol of Fe3+ and 50% of acrylamide, tensile strength and elongation at break of P(AAc-co-Am)/PVA DN hydrogels could reach 329.5 KPa and 12.9 mm/mm, respectively. These properties arise from the dynamic reversible bonds existed in the P(AAc-co-Am)/PVA DN hydrogels. These reversible bonds also give good self-healing properties, and the maximum self-healing efficiency of P(AAc-co-Am)/PVA DN hydrogels is up to 96.4%. The degradation test of synthesized DN hydrogels was also conducted under simulated physiological conditions and the weight loss could reach 74% in the simulated intestinal fluid. According to the results presented here, the synthesized P(AAc-co-Am)/PVA DN hydrogels have a potential application prospect in various biomedical fields.

Physical Organohydrogels With Extreme Strength and Temperature Tolerance

“…Therefore, improving mechanical properties of hydrogels became an important research hotspot. So far, versatile strategies to achieve tough hydrogels have been emerged, including double-network hydrogels (Gong et al, 2003;Gong, 2014;Liang et al, 2016;Chen et al, 2018;Jing et al, 2019), nanocomposite hydrogels (Haraguchi and Takehisa, 2002;Chen et al, 2015;GhavamiNejad et al, 2016;Zhu et al, 2017), topological hydrogels (Okumura and Ito, 2001;Li et al, 2018), macromolecular microsphere composite hydrogels (Huang et al, 2007;Gu et al, 2016;Zhang and Khademhosseini, 2017;Wang Z. et al, 2018), hydrophobic association hydrogels (Li et al, 2012;Mihajlovic et al, 2017;Han et al, 2018), hydrogen bonding/dipole-dipole reinforced hydrogels (Han et al, 2012;Zhang et al, 2015;Qin et al, 2018), and many others (Gong et al, 2016;Liu J. et al, 2017;Zhao et al, 2019). However, almost all of the hydrogels swollen a large amount of water in polymer networks cannot resist a cold or hot environment (Wei et al, 2014(Wei et al, , 2015Wang W. et al, 2018), hindering the application of tough hydrogels in harsh conditions.…”

Novel Self-Healing Metallocopolymers with Pendent 4-Phenyl-2,2′:6′,2″-terpyridine Ligand: Kinetic Studies and Mechanical Properties

“…The peak located at 2928 cm −1 can be attributed to the C–H stretching of the methyl and methylene groups of the polymer backbone. It should be noted that the interaction of the amide group (δ NH +ν CN ) and ν C = O in the carboxyl group leads to a shift of the C=O band (1648 cm −1 ), indicating that strong hydrogen bonds are formed between –COOH and –CONH 2 , as shown in Scheme 3 [ 23 , 44 ]. The peaks arising at 1449–1415 cm −1 , 1600–1648 cm −1 , and 531 cm −1 can be caused by asymmetric and symmetric stretching vibrations of COO groups and stretching vibrations of M–O bonds of metal-containing units in the polymer, respectively.…”

“…Among them, the inclusion of specific flexible or even switchable M–L bonds in a material is an attractive strategy for creating polymer networks with self-healing and functional properties, such as electrical conductivity [ 17 ], luminescence [ 18 ], or thermo- [ 19 ] and light-response [ 20 ]. Therefore, over the past 10 years, various types of self-healing polymers with ionic groups (ionomers) [ 21 , 22 ], double-network hydrogels [ 23 , 24 ] with different metal salts (M = Ni, Cu, Fe, Rh, Ag, etc. ), and N-heterocyclic carbenes [ 25 ] have been intensively studied [ 26 , 27 ].…”

Insight Into the Current Directions in Functionalized Nanocomposite Hydrogels

“…The physical noncovalent interactions could include hydrogen bonding, metalligand coordination, hydrophobic interaction, and π-π stacking. This is in contrast with reversible chemical covalent bonds which provide hydrogels with the self-healing properties via Diel-Alder (DA) "click chemistry, " imine bonds, boronate-catechol complexation, and other dynamic reshuffling radical reactions (Hao et al, 2019;Jing et al, 2019;Tu et al, 2019). Figure 1A schematically illustrates the strategies for the preparation of selfhealing hydrogels using intrinsic approaches (Tu et al, 2019).…”