Multiwalled carbon nanotube nucleated crystallization and reinforcement in poly (vinyl alcohol) composites

One of the fastest growing areas of nanotube research is the study of polymer-nanotube composite materials. These materials utilize the excellent strength of carbon nanotubes that has been evident but difficult to harness in the past and show impressive increases in strength relative to the polymer. It is suspected that many of the physical properties observed in these composites are related to the formation of crystalline polymer coatings around the nanotubes in solution. The work presented here addresses this issue by doping a semi-crystalline polymer, poly (vinyl alcohol), with multiwalled carbon nanotubes. Dynamic mechanical analyzer (DMA) measurements of thin films identified a three- to five-fold increase in the Young's modulus of the polymer depending on nanotube type. Dynamic differential scanning calorimetry (DSC) of thin films shows that the increase in modulus is accompanied by an increase in polymer crystallinity. In addition, the results verify that multiwalled carbon nanotubes nucleate crystallization of the polymer and a link between polymer crystallinity and composite reinforcement is established. Furthermore, transmission electron microscopy (TEM) images confirm an excellent dispersion and wetting of the nanotubes in the polymer solution providing visual evidence of matrix reinforcement.