Thermoresponsive poly(ionic liquid): Controllable RAFT synthesis, thermoresponse, and application in dispersion RAFT polymerization

The thermoresponsive poly(ionic liquid) of poly[1-(4-vinylbenzyl)-3-methylimidozolium tetrafluoroborate] trithiocarbonate (P[VBMI][BF4]-TTC) showing the soluble-to-insoluble phase transition in the methanol/water mixture at the upper critical solution temperature (UCST) was synthesized by solution RAFT polymerization and the synthesized P[VBMI][BF4]-TTC was employed as macro-RAFT agent to mediate the RAFT polymerization under dispersion condition to afford the thermoresponsive diblock copolymer nanoparticles of poly[1-(4-vinylbenzyl)-3-methylimidozolium tetrafluoroborate]-b-polystyrene (P[VBMI][BF4]-b-PS). The controllable solution RAFT polymerization was achieved as indicated by the linearly increasing polymer molecular weight with the monomer conversion and the narrow molecular weight distribution. The P[VBMI][BF4]-TTC macro-RAFT agent mediated dispersion polymerization afforded the P[VBMI][BF4]-b-PS nanoparticles, the size of which was uncorrelated with the polymerization degree of the P[VBMI][BF4] block. Several parameters including the polymerization degree, the polymer concentration and the water content in the solvent of the methanol/water mixture were found to be correlated with the UCST of the poly(ionic liquid). The synthesized poly(ionic liquid) is believed to be a new thermos-responsive polymer and will be useful in material science. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 945–954