Abstract
Polymer/ionic liquid systems are being increasingly explored, yet those exhibiting lower critical solution temperature (LCST) phase behavior remain poorly understood. Poly(benzyl methacrylate) in certain ionic liquids constitute unusual LCST systems, in that the second virial coefficient (A2) in dilute solutions has recently been shown to be positive, indicative of good solvent behavior, even above phase separation temperatures, where A2 < 0 is expected. In this work, we describe the LCST phase behavior of poly(benzyl methacrylate) in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide for three different molecular weights (32, 63, and 76 kg/mol) in concentrated solutions (5–40% by weight). Turbidimetry measurements reveal a strong concentration dependence to the phase boundaries, yet the molecular weight is shown to have no influence. The critical compositions of these systems are not accessed, and must therefore lie above 40 wt% polymer, far from the values (ca. 10%) anticipated by Flory-Huggins theory. The proximity of the experimental cloud point to the coexistence curve (binodal) and the thermo-reversibility of the phase transitions, are also confirmed at various heating and cooling rates.
Highlights
Ionic liquids (ILs) are an important class of “designer solvents”, able to access numerous desired physical properties through modest modifications of their chemical structure.ILs offer thermal, chemical, and electrochemical stability, as well as high ion conductivity and negligible volatility, thereby showing great promise as greener alternatives to traditional solvents [1,2,3,4,5]
The lower critical solution temperature (LCST)-type phase behavior of PBzMA/[BMP][TFSI] concentrated solutions was explored for three molecular weights via optical transmittance
The phase separation temperatures demonstrate a strong dependence on concentration, decreasing as the incorporation of PBzMA increases, but are not influenced by molecular weight
Summary
Ionic liquids (ILs) are an important class of “designer solvents”, able to access numerous desired physical properties through modest modifications of their chemical structure.ILs offer thermal, chemical, and electrochemical stability, as well as high ion conductivity and negligible volatility, thereby showing great promise as greener alternatives to traditional solvents [1,2,3,4,5]. Incorporating a polymer matrix into these ILs imparts structural and mechanical integrity to the resulting material, while retaining the liquid-like diffusivity of the IL [6,7,8]. This has enabled their use for separation membranes, printable electronics, battery electrolytes, and self-healing materials [9,10,11,12,13,14,15]. This growing class of smart materials poses some interesting fundamental questions. Polymer/IL systems exhibiting lower critical solution temperature (LCST) phase behavior remain poorly understood, as their behavior is not anticipated by the classical
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
