Nanosphere and nanonetwork formations of [60]fullerene-end-capped stereoregular poly(methyl methacrylate)s through stereocomplex formation combined with self-assembly of the fullerenes

We report a novel and versatile method for constructing a supramolecular nanosphere and nanonetwork based on isotactic and syndiotactic C-60-end-capped poly( methyl methacrylate)s (it- and st-PMMA-C-60's) through their stereocomplex formation combined with self-assembly of the terminal C-60. The stereoregular PMMA-C-60's with a precisely controlled structure including molecular weight, its distribution, tacticity, and the chain-end structure were synthesized by the stereospecific anionic living polymerizations of methyl methacrylate followed by end-capping with C-60, and their structures were proven by size exclusion chromatography, NMR, UV-vis, and MALDI-TOF-MS analyses. The stereoregular PMMA-C-60's self-assembled to form a core-shell aggregate with C-60 as the core and the PMMA chains as the shell in H2O/CH3CN (1/9, v/v) due to the solvophobic interaction of the C-60 units. These it- and st-PMMA-C-60 aggregates further supramolecularly assembled through iterative stereocomplex formation into nanonetworks in which the self-assembled C-60 clusters were robustly connected with two- and three-dimensional arrangements. In addition, when the it- and st-PMMA-C-60's were simultaneously mixed, self-assembly of the C-60 units and stereocomplex formation of the it- and st-PMMA chains took place at once, resulting in the formation of uniformly sized spherical nanoparticles with resistance to heat. Similar nanonetwork architectures can be produced using it- PMMA-C-60 clusters and st-PMMA prepolymers as the binder.