Arms bearing ureido-pyrimidinone functional groups with self-association capability (through quadruple hydrogen bonds) were successfully grafted onto hydroxyapatite nanoparticles. The supramolecularly modified nanoparticles (nHApUPy) exhibited enhanced colloidal stability compared to the original hydroxyapatite nanoparticles and were uniformly dispersed in supramolecular polycaprolactone in PCL(UPy)2/HApUPy nanocomposites at different filler loadings. The combined atomic force microscopy, mechanical, and rheological analyses confirmed a high degree of compatibility of HApUPy nanoparticles with the polymer matrix. The temperature dependence of the supramolecular structure in PCL(UPy)2/HApUPy nanocomposites was determined from dynamic rheological measurements at two different temperatures, 60°C and 85°C. The osteocompatibility of the nanocomposite containing HApUPy nanoparticles was compared to the pure polymer. The preliminary cell results clearly confirm that the supramolecular nanocomposites are nontoxic and biocompatible. Therefore, it is postulated that supramolecular nanocomposites provide a new way of tuning the mechanical properties of the supramolecular polymers, particularly supramolecular polycaprolactones.
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