Analysis of Non-Covalent Interactions Between the Nanoparticulate Fillers and the Matrix Polymer as Applied to Shape Memory Performance and Spun Fiber Properties

Non-covalent interactions between filler particles and polyurethanes and polypropylene (PP) were investigated using fluorescence emission spectroscopy, infra-red spectroscopy, and shear rheoloy.  The results were used in the analysis of shape memory (SM) performance of polyurethanes and mechanical properties of spun fibers of polypropylene. In the first example, composites of shape memory polyurethane (SMPU) and carbon nanofiber (CNF), oxidized carbon nanofiber (ox-CNF), organoclay, silicon carbide, and carbon black were prepared from diphenyl methane diisocyanate, 1,4-butanediol, and poly(caprolactone)diol. It was revealed by fluorescence emission spectroscopy that primarily the urethane groups located in the hard segments of SMPU interacted with the polar functional groups on filler particles. It was observed that weak non-covalent interactions of polymer chains with CNF and SiC particles caused significant reductions in soft segment crystallinity of SMPU and hence the shape memory properties of the composites.  In the second example, hydrogen-bonding interactions between sorbitol-type nucleating agents and polyhedral oligomeric silsesquioxane (POSS) were exploited to achieve nanoscale dispersion of POSS in PP, which in turn resulted in substantial improvements in spun-fiber mechanical properties.  The basic understanding developed in these studies are useful to other nanocomposite systems.