Novel nanocomposites made of boron nitride nanotubes and a physical gel

Abstract

This article describes successful incorporation of multiwalled boron nitride nanotubes (BNNTs) and various functionalized BNNTs by Lewis bases such as trioctylamine (TOA), tributylamine (TBA), and triphenylphosphine (TPP), etc., in organogels formed by triphenylenevinylene (TPV)-based low molecular weight gelator (LMWG) in toluene and consequent characterization of the resulting gel nanocomposites. Functionalized BNNTs were synthesized first, and the presence of tubular structures with high aspect ratio and increased diameter compared to the starting BNNTs was confirmed by SEM, TEM, and Raman spectroscopy. The micrographs of composites of 1 and BNNTs showed evidence of wrapping of the gelator molecules on to the BNNT surface presumably brought about by p-p stacking and van der Waals interactions. This leads to the formation of densely packed and directionally aligned fibrous networks. Such 'reinforced' aggregation of the gelator molecules in presence of doped BNNTs led to an increase in the sol-to-gel transition temperature and the solidification temperature of the gel nanocomposites as revealed from differential scanning calorimetry. Rheological investigations of the gel nanocomposites indicate that the flow properties of the resulting materials become resistant to applied stress upon incorporation of even a very low wt % of BNNTs. Finally, the increase in thermal conductivity of the nanocomposite compared to the gelator alone was observed for the temperature range of 0-60 °C which may make these composites potentially useful in various applications depending on the choice and the amount of BNNT loading in the composite.