Nanocomposites use nanomaterials with characteristic lengths in nanometers resulting in a high surface-to-volume ratio. Furthermore, the large filler/matrix interface reduces the interparticle distances lower than the radius of gyrations of polymers, thus changing the polymer chain conformation. Therefore, the incorporated nanofillers can fundamentally alter the characteristics of polymers and realize remarkable performances compared to conventional composites. However, ironically, the large interfacial area makes it challenging for the interplay of enthalpic and entropic contributions of the filler and polymer matrix. Unfortunately, this causes phase separation and agglomeration of nanoparticles, compromising the properties of nanocomposites. Therefore, it is essential to tailor the thermodynamic driving forces at the filler/matrix interfaces to achieve desired morphology and, ultimately, enhanced physical properties. Here, I introduced functional organic-inorganic nanocomposites consisting of nanoscopically dispersed functional nanoparticles through the design of filler/matrix interfaces. Thanks to the uniform dispersion of nanoparticles, the presented nanocomposites displayed multifunctionalities, such as electrical conductivity with mechanical flexibility, degradability with scalability, and simultaneous enhancement of strength and ductility, which are generally mutually exclusive.

This dissertation details the effects of obesity on the mechanical properties and structure of cortical bone. Obesity is associated with greater bone mineral content that might be expected to protect against fracture, which has been observed in adults. Paradoxically however, the incidence of bone fractures has been found to increase in overweight and obese children and adolescents. Femora from adolescent and adult mice fed a high-fat diet are investigated for changes in shape, tissue structure, as well as tissue-level and whole-bone mechanical properties. Results indicate increased bone size, reduced size-independent mechanical properties, but maintained size-dependent mechanical properties. Other changes in cortical bone response to obesity are observed with advancing age. This study indicates that bone quantity and bone quality play important compensatory roles in determining fracture risk, and that fracture risk may not be lessened for adults as previously thought.