SURFACE GRAFTED POLY(IONIC LIQUID) THAT LUBRICATES IN BOTH NON-POLAR AND POLAR SOLVENTS

Following a series of studies concerning the tribological characteristics of polyzwitterionic brushes [1-4], we show that 1-n-butyl-3-vinyl imidazolium bromide based poly(ionic liquids) (PIL) samples is able to reduce the interfacial friction by up to 66% and 42% in both non-polar (dodecane) and polar (water) solvents respectively [5]. This is unusual for surface grafted polymer that delivers lubrication when the polymer chains are well solvated. Both chemical moieties and polymerisation time could influence the lubrication introduced by the PIL brushes. AFM based force spectroscopy reveals that the polymer brush adopts distinctively different interfacial conformations: swollen in water but collapsed in dodecane. However, minimal surface adhesion was observed with both polymer conformations, which can be attributed to steric repulsion as the result of a swollen conformation in water, or surface solvation when the hydrophobic fraction of the polymer was exposed to the dodecane. The work brings additional insight on polymer lubrication mechanism, which expands the possible design of polymer architecture for interfacial lubrication and modification.

1. Zhang et al. Langmuir 2011, 27, 2514

2. Zhang et al. Langmuir 2013, 29, 10684

3. Zhang et al. Langmuir 2016, 32, 5048

4. Zhang et al. Langmuir 2017, 33, 706  

5. Burgess et al. ACS Macro Lett. 2021, 10, 907