Supramolecular Approach to Polymer-Shape Transformation via Calixarene–Fullerene Complexation

We synthesized fullerene-terminated polymethyl methacrylates (PMMAs), linear ditopic calix[5]­arene host, and branched tritopic calix[5]­arene host. The calix[5]­arene hosts bound to the fullerene moieties of the PMMAs, inducing shape transformation among three different polymer shapes, namely, short PMMA, long PMMA, and star-shaped PMMA, in solution. The transformation was studied using UV/vis spectroscopy, fluorescence spectroscopy, diffusion ordered NMR spectroscopy, size-exclusion chromatography, viscometry, and differential scanning calorimetry. Dynamic light scattering measurements confirmed that the transformation between the individual shapes was induced by application of external stimuli, including prechosen molecules and heating of the solution. Of particular note is that atomic force microscopy revealed that PMMA illustrated an additional shape, namely, a spherical shape, in the solid state due to the cohesive nature of its fullerene moiety. The present study illustrated that a supramolecular approach to polymer-shape regulation allows access to multiple distinct polymer shapes in sequence.