Thermoresponsive polymerized gemini dicationic ionic liquid

Yongjun Men,Antje Voelkel,Jiayin Yuan,Helmut Schlaad

doi:10.1039/c3py01790g

Abstract

A new type of gemini poly(ionic liquid), poly[(1,8-octanediyl-bis(tri-n-butylphosphonium) 4-styrene sulfonate], was synthesized via the free radical polymerization of a dicationic ionic liquid monomer in DMF. This poly(ionic liquid) presented a lower critical solution temperature (LCST)-type phase transition in aqueous solution. Unusually this phase transition can be observed even at a concentration as low as 0.1 wt%. Additionally, the type and concentration of external salt can influence the cloud point. Copolymerisation of this gemini dicationic ionic liquid monomer with divinylbenzene crosslinker in water led to the formation of a hydrogel, which exhibited a temperature-triggered volume change in water.

Highlights

E-mail: jiayin.yuan@mpikg. mpg.de; Fax: +49-331-5679502; Tel: +49-331-5679552 when mixed with cyclodextrin in water, showed a pseudo-lower critical solution temperature (LCST) effect.[14]
The nal product poly(SS-P2) used in this work was synthesized via conventional free radical polymerization of SS-P2 in DMF at 90 C using AIBN (0.4 wt% with respect to monomer) as the initiator
The methyl protons (ÀCH3) at the end of the butyl chain appear at 0.9 ppm, Fig. 1 1H-NMR (400.1 MHz, D2O) spectra of P2-Br (A), SS-P2 (B) and poly(SS-P2) (C)

Summary

Introduction

Thermoresponsive polymers, which usually display a reversible phase transition in their solution at a speci c temperature, have received major interest in the past two decades.[1,2,3,4,5] Generally speaking, water-soluble thermoresponsive polymers are of special interest with respect to their wide applications in tissue engineering, controlling systems and sensing devices.[6,7,8] The best known examples of these polymers are poly(N-isopropylacrylamide) (PNIPAM) and the poly(meth)acrylamide derivatives with hydrogen-bonding properties and hydrophobic interactions, which exhibit a lower critical solution temperature (LCST) behavior in aqueous solution.[6,9,10,11,12] Except for zwitterionic polymers, like poly[3-(N-(3-methacrylamidopropyl)-N,N-dimethylammonio)-propanesulfonate], most thermoresponsive polymers themselves are nonionic in bulk.Conventional polyelectrolytes are water-soluble polymers carrying ionizable functionalities along the polymer chain, which have a wide range of applications, such as water puri cation, oil recovery, pigment removal, paper making, layer-bylayer technology and so on. Thermoresponsive polymers, which usually display a reversible phase transition in their solution at a speci c temperature, have received major interest in the past two decades.[1,2,3,4,5] Generally speaking, water-soluble thermoresponsive polymers are of special interest with respect to their wide applications in tissue engineering, controlling systems and sensing devices.[6,7,8] The best known examples of these polymers are poly(N-isopropylacrylamide) (PNIPAM) and the poly(meth)acrylamide derivatives with hydrogen-bonding properties and hydrophobic interactions, which exhibit a lower critical solution temperature (LCST) behavior in aqueous solution.[6,9,10,11,12] Except for zwitterionic polymers, like poly[3-(N-(3-methacrylamidopropyl)-N,N-dimethylammonio)-propanesulfonate], most thermoresponsive polymers themselves are nonionic in bulk. Aoshima et al synthesized poly(vinyl ether)s with pendant imidazolium salt moieties, which presented an upper critical solution temperature (UCST) or LCST phase separation in organic solvents of speci c polarity.[13] By changing the anion to tetra uoroborate in these polymers, a UCST-type phase separation in water was observed. The cyclodextrin ring complexed with the large-sized hydrophobic Tf2N anion at low temperature to make the polymer soluble in water, and slipped off at high temperature returning the polymer to its hydrophobic state and making it insoluble in water again

Methods

Results

Conclusion