Directly and quantitatively studying the interfacial interaction between SiO2 and elastomer by using peak force AFM

The interfacial interaction between nanofillers and elastomer plays an important role in properties of elastomer nanocomposites. Up to now, most methods focus on studying the interphase of elastomer nanocomposites. The filler-elastomer interaction forces have not been directly and quantitatively characterized yet. In this study, the interaction forces at nano-Newton scale between elastomer matrix and silica (SiO2) were directly and quantitatively characterized by using peak force quantitative nanomechanical mapping (PF-QNM) mode of atomic force microscopy (AFM). Three kinds of nitrile butadiene rubber (NBR) molecules with different molecular polarity were first grafted on the AFM tip by using click chemistry. The SiO2 (or modified SiO2) were pressed into flat films and worked as substrate. The interaction forces between these NBR layer grafted on AFM tip and SiO2 (or modified SiO2) substrate were directly and quantitatively obtained. The results show that as the acrylonitrile content of NBR increasing from 26 wt% to 41 wt%, the average interaction force of NBR/SiO2 increases from 4.5 +/- 1.0 nN to 7.7 +/- 1.1 nN and that of NBR/m-SiO2 increases from 6.2 +/- 1.2 nN to 12.9 +/- 1.0 nN. This study provides guidance in direct and quantitative characterization of filler-elastomer interactions at nano-Newton resolution.