Origin of Surface Charge of Double Network Hydrogels Prepared by Sequential Polymerization

Abstract

Understanding the physicochemical properties of hydrogel surfaces and their molecular origins is important for their applications. In this paper, we elucidate the molecular origin of surface charges in double-network hydrogels synthesized by two-step sequential polymerization. Synthesis of hydrogels by free-radical polymerization does not fully complete the reaction, leaving a small number of unreacted monomers. When this approach is used to synthesize double network (DN) hydrogels by a two-step sequential polymerization from charged monomers for the first network and neutral monomers for the second network, the unreacted first network monomers are incorporated into the second network. Since the surface of such DN hydrogels is covered with a μm-thick layer of the neutral second network, the incorporation of a small amount of charged monomers into the second network increases the surface charge and, thereby, their repulsive/adhesive properties. Therefore, we propose a method to remove unreacted monomers and modulate the surface charge density of DN hydrogels.

Polymer mechanochemistry: from single molecule to bulk material

“…43 To realize the force-triggered surface microstructure growth, the researchers first successfully prepared a DN structure at the surface using a surface-bulk transition strategy. 44,45…”

Cascade Reaction of Thiol–Disulfide Exchange Potentiates Rapid Fabrication of Polymer Hydrogels

“…Polymer hydrogels that can entrap large amounts of water without losing the integrity of the cross-linked networks have attracted great interests in biomedical applications, − such as hemostasis, tissue engineering, and therapy. − Noncovalent (e.g., hydrogen bonding and electrostatic interaction) and covalent (e.g., amide bond and Schiff base) interactions have been integrated in the engineering of functional polymer hydrogels. − Poly­(ethylene glycol) (PEG) as a low-fouling polymer has been widely used for the engineering of functional hydrogels. , For example, dynamic PEG hydrogels were fabricated via click reaction and hydrogen bonding . However, the terminal end groups of PEG are limited, resulting in low reaction rates and high critical gelation concentrations (CGCs).…”