Micelle/inverse micelle self-assembly of a PEO-PNIPAm block copolymer in ionic liquids with double thermoresponsivity

Hau Nan Lee, Zhifeng Bai, Nakisha Newell, Timothy P. Lodge

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


We report a doubly thermoresponsive diblock copolymer that exhibits both an upper critical micellization temperature (UCMT) and a lower critical micellization temperature (LCMT) in ionic liquids. Dynamic light scattering and cloud point measurements are employed to investigate the micellization behavior of poly(ethylene oxide)-b-poly(N-isopropylacrylamide) (PEO-PNIPAm) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]), and their blends. In a single ionic liquid solvent, at low and high temperatures, the block copolymer self-assembles into PNIPAm-core and PEO-coremicelles, respectively. The core and corona of themicelles are reversibly switchable in response to the stimulus of temperature. Using [EMIM][BF4]/[BMIM] [BF4] blends as solvents, both theUCMTs andLCMTscan be easily tuned over a wide range of temperature by varying themixing ratio of the two ionic liquids.Depending on the relative positionsof theUCMTandLCMT, twotypes of doubly thermoresponsive systems (micelle-unimerinverse micelle and micelle-copolymer aggregates-inverse micelle) can be obtained.

Original languageEnglish (US)
Pages (from-to)9522-9528
Number of pages7
Issue number22
StatePublished - Nov 23 2010


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