Tunable doubly responsive UCST-type phosphonium poly(ionic liquid): a thermosensitive dispersant for carbon nanotubes

Abstract

Poly(triphenyl-4-vinylbenzylphosphonium chloride) synthesized via RAFT polymerization exhibits both tunable halide ion- and thermo-responsiveness (UCST-type) in aqueous solution and acts as a thermosensitive stabilizer for carbon nanotubes.

How to manipulate the upper critical solution temperature (UCST)?

“…Also, the presence of increasing amounts of cosolvents such as methanol, dimethylformamide, or dimethyl sulfoxide decreased the cloud points. 44 Halide ions can induce UCST behavior in branched polyethyleneimine (PEI) or partially quaternized PEI, under highly acidic ( pH < 0.6) conditions (Fig. 6).…”

“…HBr and HI are more efficient in inducing a cloud point than HCl. When PEI is functionalized with 35 to 38% permanent Poly(triphenyl-4-4vinylbenzyl phosphonium chloride) 44 and polyethyleneimine 45 (top) exhibit UCST behavior in the presence of various halide anions (below, presented with their respective effective radii).…”

Chemical Tuning of Zwitterionic Ionic Liquids for Variable Thermophysical Behaviours, Nanostructured Aggregates and Dual‐Stimuli Responsiveness

“…It is, therefore, expectedt hat these ZIL would show some kind of responses toward foreigna nions as many cationic poly(ionic liquids) (PILs) also do due to intra-and/or inter-chain ionic cross-linkingb etween the neighbouring PIL chainst hrough the excessf oreigna nions. [64][65][66] Unfortunately, we did not observea ny turbidity formation upon addition of variousi norganic ions, such as NO 3 À ,C l À ,B r À ,I À ,S CN À ,C lO 4 À and SO 4 2À up to ac oncentration of 5.0 m into the aqueous ZIL solutions( 1wt%). This observation may suggest ap oor stability of the small molecular ZIL aggregates through ionic bridging in the presence of foreign anion;w hereas ionically bridged PIL aggregates in the presence of foreigni ons are stable enough to give turbid suspension in water.F urther,i tw as noticed that upon addition of large hydrophobic ion, such as NTf 2 À (Tf = triflate), the ZIL molecules get coagulated and phase separated out from their aqueous solution and remained precipitated upon heatingu pt oa pproximately 90 8C.…”

“…In this context, it is understood that there should not be any deprotonation of attached carboxylic acids in the acidic pH region, that is, below the pI, thus the ZIL molecules can be considered as ILs containing imidazolium cations and Br − counterions. It is, therefore, expected that these ZIL would show some kind of responses toward foreign anions as many cationic poly(ionic liquids) (PILs) also do due to intra‐ and/or inter‐chain ionic cross‐linking between the neighbouring PIL chains through the excess foreign anions . Unfortunately, we did not observe any turbidity formation upon addition of various inorganic ions, such as NO 3 − , Cl − , Br − , I − , SCN − , ClO 4 − and SO 4 2− up to a concentration of 5.0 m into the aqueous ZIL solutions (1 wt %).…”

Functionalization of Carbon Nanotubes with Stimuli- Responsive Molecules and Polymers

“…The authors claimed that this method was advantageous in terms of allowing precise and designable control of CNT dispersion over a wide temperature range and at a desired temperature. [Cl]s) ( Figure 17A) [91]. These polymers showed double responsiveness towards halide ions and temperature (upper critical solution temperature-type) in aqueous solution.…”