Simple spectrophotometric method for the estimation of accessible amino groups and preparation of polyurethane nanocomposites.

Carboxylic-functionalyzed task-specific imidazolium ionic liquids (carboxylic-IL) presented selective high reactivities with epoxy-functionalized compounds, even in highly complex epoxy-silica nanocomposite systems. The carboxylic-IL induced the in situ covalent bonding with epoxy based materials and tuning the nanocomposites' filler-matrix interphase when applied either via hydrolytic or non-hydrolytic sol-gel process. Structural modifications in the carboxylic-IL allowed fine morphology control and promoted the formation of well dispersed silica nanodomains. This approach resulted in nanocomposites with improved mechanical properties, without negative effect on the glass transition temperature, for both rubbery and glassy epoxy-silica nanocomposite systems with a very small IL content (~0.2 wt.-%). The best properties were achieved with the application of IL 1-carboxypropyl-3-methylimidazolium chloride, which produced toughness increase of more than 7 times for the rubbery and almost twice for the glassy epoxy systems, when compared to their ILfree equivalents. These easy and quick procedures to produce imidazolium functionalized materials have the potential to open a broad range of new conductive, responsive, smart and tune-reinforced materials. Fig. 9 Time dependent FTIR spectra of the reaction between PGE and C3H6CO2HMImCl. Curves represent measurements at 30 min, 1 h, 5 h, 24 h and 48 h. Scheme 1 Sumary of characteristics of the epoxy-silica formed via hydrolytic and non-hydrolytic sol-gel process in the presence of IL.Scheme 2 Schematic representation of the interphase compositions depending on the IL applied, based on a sequence of covalent and physical bonds.