Poly(Ionic Liquid) Semi-Interpenetrating Network Multi-Responsive Hydrogels

• Main Authors: Alexandru Tudor, Larisa Florea, Simon Gallagher, John Burns, Dermot Diamond
• Format: Article
• Language: English
• Published: MDPI AG 2016-02-01
• Series: Sensors
• Subjects: smart materials; hydrogels; poly(ionic liquid)s; LCST; polyelectrolyte effect; stimuli-responsive
• Online Access: http://www.mdpi.com/1424-8220/16/2/219

Herein we describe poly(ionic liquid) hydrogel actuators that are capable of responding to multiple stimuli, namely temperature, ionic strength and white light irradiation. Using two starting materials, a crosslinked poly ionic liquid (PIL) and a linear poly(N-isopropylacrylamide-co-spiropyran-co-acrylic acid), several semi-interpenetrating (sIPN) hydrogels were synthesised. The dimensions of hydrogels discs were measured before and after applying the stimuli, to quantify their response. Samples composed of 100% crosslinked PIL alone showed an average area reduction value of ~53% when the temperature was raised from 20 °C to 70 °C, ~24% when immersed in 1% w/w NaF salt solution and no observable photo-response. In comparison, sIPNs containing 300% w/w linear polymer showed an average area reduction of ~45% when the temperature was raised from 20 °C to 70 °C, ~36% when immersed in 1% NaF w/w salt solution and ~10% after 30 min exposure to white light irradiation, respectively. Moreover, by varying the content of the linear component, fine-control over the photo-, thermo- and salt response, swelling-deswelling rate and mechanical properties of the resulting sIPN was achieved.