Selective Mechanical Reinforcement of Thermoplastic Polyurethane by Targeted Insertion of Functionalized SWCNTs

We have prepared composites from a thermoplastic polyurethane reinforced with functionalized single walled nanotubes. Nanotubes with two types of functional groups were used: water-soluble tubes functionalized with polyethyleneglycol or poly(amino benzene sulfonic acid) and tetrahydrafuran-soluble tubes functionalized with octadecylamine. Composites prepared with water- or tetrahydrafuran-soluble tubes showed markedly different properties. Addition of water-soluble tubes tended to result in crystallization of the polyurethane soft segments, whereas addition of the tetrahydrafuran-soluble tubes promoted crystallization of the polyurethane hard segments. We interpret this as evidence of selective insertion of tubes in either hard or soft segments depending on the surface chemistry of the (functionalized) nanotube and the chemical structure of the segment. This interpretation is supported by differences in the mechanical properties of the composites. The water-based composites tend to be stiffer and display ...