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Open AccessArticle

Ultrasound- and Thermo-Responsive Ionic Liquid Polymers

Department of Applied Chemistry, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
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Polymers 2018, 10(3), 301; https://doi.org/10.3390/polym10030301
Received: 24 February 2018 / Revised: 9 March 2018 / Accepted: 9 March 2018 / Published: 11 March 2018
(This article belongs to the Special Issue Stimuli Responsive Polymers)
Poly(sodium 2-acrylamido-2-methylpropanesulfonate) (PAMPSNa) was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. An ionic liquid polymer (PAMPSP4448) was then prepared by exchanging the pendant counter cation from sodium (Na+) to tributyl-n-octylphosphonium (P4448+). We studied the ultrasound- and thermo-responsive behaviors of PAMPSP4448 in water. When the aqueous PAMPSP4448 solution was heated from 5 to 50 °C, the solution was always transparent with 100% transmittance. Unimers and interpolymer aggregates coexisted in water in the temperature range 5–50 °C. Generally, hydrogen bonding interactions are broken as the temperature increases due to increased molecular motion. Above 25 °C, the size of the interpolymer aggregates decreased, because hydrophobic interactions inside them were strengthened by dehydration accompanying cleavage of hydrogen bonds between water molecules and the pendant amide or sulfonate groups in PAMPSP4448. Above 25 °C, sonication of the aqueous solution induced an increase in the collision frequency of the aggregates. This promoted hydrophobic interactions between the aggregates to form larger aggregates, and the aqueous solution became turbid. When the temperature was decreased below 8 °C, hydrogen bonds reformed between water molecules and the pendant amide or sulfonate groups, allowing PAMPSP4448 to redissolve in water to form a transparent solution. The solution could be repeatedly controlled between turbidity and transparency by sonication and cooling, respectively. View Full-Text
Keywords: thermo-responsive; ultrasound; reversible addition-fragmentation chain transfer (RAFT) polymerization; ionic liquid polymer; electrostatic repulsion; hydrophobic interaction; lower critical solution temperature (LCST) thermo-responsive; ultrasound; reversible addition-fragmentation chain transfer (RAFT) polymerization; ionic liquid polymer; electrostatic repulsion; hydrophobic interaction; lower critical solution temperature (LCST)
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MDPI and ACS Style

Itsuki, K.; Kawata, Y.; Sharker, K.K.; Yusa, S.-I. Ultrasound- and Thermo-Responsive Ionic Liquid Polymers. Polymers 2018, 10, 301.

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