What will happen when thermoresponsive poly( N -isopropylacrylamide) is tethered on poly(ionic liquid)s?

The thermoresponsive ionic liquid diblock copolymer of poly[1-(4-vinylbenzyl)-3-methylimidazolium tetrafluoroborate]- block -poly( N -isopropylacrylamide) (P[VBMI][BF 4 ]- b -PNIPAM) containing a hydrophilic poly(ionic liquid) block of P[VBMI][BF 4 ] is prepared by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization. This P[VBMI][BF 4 ]- b -PNIPAM exhibits an abnormal thermoresponsive phase transition at a temperature above the phase transition temperature (PTT) of the PNIPAM block. For P[VBMI][BF 4 ]- b -PNIPAM including a short P[VBMI][BF 4 ] block, its aqueous solution becomes turbid at a temperature above the PTT of the thermoresponsive PNIPAM block, whereas for P[VBMI][BF 4 ]- b -PNIPAM containing a relatively long P[VBMI][BF 4 ] block even in the case of a relatively long PNIPAM block, the aqueous solution remains transparent at a temperature far above the PTT of the PNIPAM block, although a soluble-to-insoluble phase transition of the PINIPAM block is confirmed by dynamic light scattering (DLS) analysis and variable temperature 1 H NMR analysis. The reason that P[VBMI][BF 4 ]- b -PNIPAM exhibits an abnormal thermoresponse is discussed and ascribed to the highly hydrophilic and charged poly(ionic liquid) block of P[VBMI][BF 4 ] leading to the formation of small-sized micelles at a temperature above the PTT.