(193o) Effect of Salts on Material Properties and Responsive Behavior of Interpenetrating Polymer Network Hydrogels

Environmentally responsive hydrogels have a variety of applications due to their unique dynamic swelling behaviors upon external stimuli. Salt additives during synthesis can play a key role in shaping the swelling behavior of a hydrogel system in terms of the degree of swelling and the rate of the responsiveness. Herein we report the effects of different salts in synthesizing an UCST characteristic interpenetrating polymer network (IPN) hydrogel consisting of polyacrylamide (PAAm) and poly (acrylic acid) (PAAc). The volume transition is remotely triggered by visible-light irradiation through the addition of photochromic particles, such as gold nanoparticles and carbon black. The presence of sodium chloride from the solution can result in ions surrounding the polar sections of the network, forming an electrostatic screen, making the network more elastic and allowing for greater swelling. Additionally, incorporating sodium hydroxide in the synthesis as a strong ionizing agent can amplify the volume transition by ionizing the PAAc, strengthening the hydrogen bonds between chains of PAAc and PAAm. The resulting modifications on the thermal and mechanical properties can be utilized to tailor the swelling behavior and improve the material strength of the IPN hydrogel for potential applications, such as actuators and tactile displays.