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

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Physicochemical properties of hydrogel surfaces are crucial for their applications.
• Understanding the molecular origins of these properties is essential for material design.
• Double-network (DN) hydrogels are advanced materials with tunable properties.

Purpose of the Study:

• To elucidate the molecular origin of surface charges in DN hydrogels synthesized via two-step sequential polymerization.
• To investigate the impact of unreacted monomers on surface charge density and properties.
• To propose a method for removing unreacted monomers and controlling surface charge.

Main Methods:

• Two-step sequential polymerization using charged monomers for the first network and neutral monomers for the second.
• Analysis of unreacted monomer incorporation into the second network.
• Development of a method to remove unreacted monomers from DN hydrogels.

Main Results:

• Unreacted charged monomers from the first network are incorporated into the neutral second network during synthesis.
• This incorporation leads to increased surface charge density in DN hydrogels.
• The presence of charged monomers in the second network influences the repulsive/adhesive properties of the hydrogel surface.

Conclusions:

• The surface charge of DN hydrogels is significantly influenced by residual unreacted monomers from the first network.
• A method to remove these monomers can effectively modulate the surface charge density.
• Controlling surface charge offers a pathway to tailor the performance of DN hydrogels in various applications.