Enhanced Mechanical Properties by Ionomeric Complexation in Interpenetrating Network Hydrogels of Hydrolyzed Poly (N-vinyl Formamide) and Polyacrylamide

Abstract

Tough hydrogels were made by hydrolysis of a neutral interpenetrating network (IPN) of poly (N-vinyl formamide) PNVF and polyacrylamide (PAAm) networks to form an IPN of polyvinylamine (PVAm) and poly (acrylic acid) (PAAc) capable of intermolecular ionic complexation. Single network (SN) PAAm and SN PNVF have similar chemical structures, parameters and physical properties. The hypothesis was that starting with neutral IPN networks of isomeric monomers that hydrolyze to comparable extents under similar conditions would lead to formation of networks with minimal phase separation and maximize potential for charge–charge interactions of the networks. Sequential IPNs of both PNVF/PAAm and PAAm/PNVF were synthesized and were optically transparent, an indication of homogeneity at submicron length scales. Both IPNs were hydrolyzed in base to form PVAm/PAAc and PAAc/PVAm IPNs. These underwent ~5-fold or greater decrease in swelling at intermediate pH values (3–6), consistent with the hypothesis of intermolecular charge complexation, and as hypothesized, the globally neutral, charge-complexed gel states showed substantial increases in failure properties upon compression, including an order of magnitude increases in toughness when compared to their unhydrolyzed states or the swollen states at high or low pH values. There was no loss of mechanical performance upon repeated compression over 95% strain.

Synthesis of dual physical self‐healing starch‐based hydrogels for repairing tissue defects

“…In this measurement, a 5 N load cell was used; samples were shaped like a dumbbell by a gauge length of 20 mm, a width of 10 mm, and a diameter of 5 mm and extended at a rate of 100 mm min −1 . [ 2,15 ]…”

“…Compared to other studied hydrogels, these hydrogels have shown all the properties at once. [ 2 ] The availability of two networks with different properties and physical connections constitutes its unique feature. Hydrogels with other properties can be achieved by changing the network and bonds.…”

Oxygen-Tolerant Fabrication of Large-Area Hydrogel Films via Photoinduced Electron/Energy Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization

“…The cross-linking density of the prepared PAAm was also calculated based on the Mooney−Rivlin equation 38,39 ( )…”

Design of Magnetic Hydrogels for Hyperthermia and Drug Delivery

“…Similarly, when at least one polymer face is cross-linked and the other phase remains non-cross-linked the system is called a semi-interpenetrating polymer network (semi-IPN) [ 79 ]. When compared to semi-IPN systems, IPNs are always superior in terms of mechanical strength [ 80 ]. Gel matrices are very vulnerable to water, drug molecules, and a variety of hydrophilic small molecules due to the presence of hydrophilic polymer chains [ 81 ].…”