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DOSS–(dioctyl sulfosuccinate) based quaternaryammonium ionic liquids (QAILs) were synthesized and used as both neatlubricants and lubricant additives. The influence of structure ontheir miscibility, thermal stability, and tribological property wasdiscussed. These QAILs are low cost as compared with conventionalhalogen-containing ionic liquids (ILs). They are noncorrosive andhydrolysis stable because of their halogen-free characteristics. Thetribological properties of these QAILs as neat lubricants for steel/steeland steel/copper contacts are found to be better than conventionalhalogen-containing ILs 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(L-F104) and far better than traditional synthetic lubricant poly-α-olefin(PAO). Moreover, oil-soluble ILs were obtained by properly adjustingthe chain length and cation asymmetry of these QAILs, which can beeasily dissolved in nonpolar synthetic-oil PAO. They are found tobe effective lubricant additives for improving the friction-reducingand antiwear properties of PAO. It is a great advantage as comparedwith conventional ILs, which have extremely low solubility in PAOand are difficult to be used as lubricant additives for this kindof base oil. Furthermore, the coking test results indicated that thesynthesized QAILs have high deterging ability when used as lubricantadditives for PAO. Thus, they can restrain carbonaceous depositionas well as oil sludge and varnish formation on the metal contactsduring the sliding process. They can also disperse, loosen, and removethe already formed harmful substances and keep the metal contactsclean. The present work may make obvious progress toward preparinglow cost, noncorrosive, and environmentally benign IL lubricants inlubrication engineering. [ABSTRACT FROM AUTHOR]

Thefabrication of core/shell charged polymer brushes-grafted hollowsilica nanoparticles (PSPMA-g-HSNPs) is reported.Because of the excellent hydration capability of the shells consistingof charged polymer brushes, the functional nanoparticles can achievea good lubricating effect in aqueous media via hydration lubricationmechanism. The mesoporous hollow silica cores endow the nanoparticleswith drug loading–release capability. Aspirin, as a usefuldrug for treating arthritis, was employed to carry out in vitro drugloading and release studies. It is clear that brushes-modified hollowsilica exhibited long-term drug release performance. The combinationof lubrication and drug loading capabilities results in the greatclinical potential of new multifunctional nanoparticles as injectablejoint lubricant fluid in arthritis treatment. [ABSTRACT FROM AUTHOR]

We present a paradigm that dramaticallytunes friction from superior lubrication (μ ∼ 10–3) to ultrahigh friction (μ > 1) using responsivepolyelectrolyte brushes. The tunable friction is based on counterion-driveninteractions in polyelectrolyte brushes that can be simply achievedby exchanging the counterions. We systematically investigated theeffects of opposite counterions of different types on the frictionproperties of polyanionic, polycationic, and polyzwitterionic brushes.For cationic brushes with quaternary ammonium groups, the frictioncoefficient was progressively tuned from ∼10–3to ∼100according to the counterions series Cl–< ClO4–< PF6–< TFSI–. The frictionof anionic brushes can be tuned by oppositely charged surfactants(tetraalkylammonium) with different length of hydrophobic tails, multivalentmetal ions, and protons. The friction increase of cationic brushesis due to the dehydration and the collapse of polyelectrolyte chainsinduced by ion-pairing interactions. For anionic brushes, the frictionincreased with the length of hydrophobic tails of surfactants, whichresulted from hydrophobicity induced electrostatic interaction amongsurfactants and polymer chains. The anionic brushes with the carboxylateand the sulfonate side groups revealed different friction responses,which is owing to the carboxylate groups getting stronger specificinteraction with the quaternary ammonium and thus with the multivalentmetal ions as well. The mechanism of tuning friction was finally concluded;that is, highly hydrated and swelling polymer brushes show superiorlubrication, partially collapsed polymer chains have moderate lubrication,and completely dehydrated and collapsed conformation loses lubricatingcapability. [ABSTRACT FROM AUTHOR]