Polymer nanocomposites can be used in a variety of areas such as coating, medical implants, optics, drug delivery, aerospace, semiconducting materials and textiles. Certain nanoparticles (e.g., carbon nanotubes (CNTs), clay, metal, and graphene) are also used as reinforcement in a new class of polymer nanocomposites with enhanced properties compared to conventional composites. For example, carbon fibres, carbon black, carbon nanotubes and (multilayer) graphene can be used as additives to change the polymer's mechanical and electrical properties.  The polymer composite can then be extruded into threads that can be used in textiles.  Hence, smart textiles can be achieved if one can manufacture polymeric threads with desired properties.

Present methods of manufacturing polymer nanocomposites to not produce threads with optimal properties.  For example, the threads are not as strong as is expected from theoretical calculations, nor do they conduct electricity with the expected efficiency.  A huge amount of experimental and theoretical research is therefore being conducted in this field. This is because there are a large range of parameters that affect the properties of the composite. Examples of these parameters are the length, chirality, dispersion and alignment of the CNTs and the viscosity of the polymer matrix. The effect of these parameters needs to be understood and controlled to optimise the material properties of the composite. For instance, different results are reported for Young’s modulus of nanocomposites when using nanotubes as composites, and this often depends on the functional groups that can be attached to the CNTs.

Computer simulations complement experiment by deepening our understanding of the way that additives change the nanocomposite properties. We are performing molecular-scale calculations in order to understand the additive-additive and additive-polymer interactions, in an effort to understand these interactions and to identify ways to modify these interactions in order to optimise the properties of the textile threads. Our research focuses on single wall carbon nanotubes (SWNTs) added to different polymers such as polyethylene (PE) and polyvinylidene fluoride (PVDF). As an essential step to design nanocomposites with desired properties, we are evaluating the validity of empirical force fields  with the aid of first principles methods. Reliable force field are subsequently used to study the effect of the additive on the composite properties. A hierarchical approach, bridging the gap between the atomic and macro scales, is also being developed.

This research, which is done in collaboration with experiment, is funded by the Swedish Foundation for Strategic Research and The Swedish Research Council.