Molecular Design of Hybrid Dielectrics at the Extreme Limits of Molecular-scale Confinement
Pr Reinhold H. Dauskardt
Ruth G. and William K. Bowes Professor
Materials Science, Mechanical Engineering and Surgery
Stanford University and the Stanford School of Medicine
We review the state-of-the-art in the molecular design and processing of low density organic-inorganic hybrid dielectrics at the extreme limits of molecular-scale confinement including asymmetric elastic and thermal expansion properties that are inherently related to terminal chemical groups in confinement. We describe a new nanoscale design principle using hyperconnected molecular architectures to achieve remarkable mechanical properties controlled by designing connectivity into the intrinsic molecular structure in innovative ways. We probe the mechanical and fracture properties of hybrids in the extreme limits of molecular confinement, where a stiff inorganic matrix phase confines polymer chains to dimensions far smaller than their bulk radius of gyration. Finally, we describe a synthesis strategy which involves the infiltration of individual polyimide precursors into a nanoscale porous network where imidization reactions under such confinement increase the molecular backbone stiffness and provide unique high temperature properties.