Solvent-free nanofluids with surface functional groups composed of tetraalkylammonium ionic liquid organic salts and isothiocyanate decorating nanosilica cores are reported that exhibit viscous flow and glass transitions. These nanofluids when combined with hexamethylene diisocyanate and isophorone diisocyanate-polypropyleneglycol prepolymers are coated and autocured in humid air to produce thin films and clearcoats. These new resins are characterized thermally and by nanoindentation. Relative to the air-cured prepolymer control, low nanofluid loading (1-4% w/w) produces increased storage moduli and hardness and decreased loss factors. High loading (8 and 16%) results in softening with increased toughness. While the control exhibited marked viscoelastic recovery, this recovery was largely arrested in the nanocomposite coatings. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3439-3448