(17a) Layer-by-Layer Assembled Macroscale Materials with Microscale 3D Topologies

Hybrid nanocomposites create functional materials with enhanced and diversified properties as compared to their bulk counterparts. Three-dimensional topology adds to these impressive properties by allowing for the addition of unique characteristics such as special deformation patterns, negative Poison’s ratio, negative thermal coefficient, propagation of electromagnetic waves, biological, and mass transport properties. Typical methods for preparing materials with 3D microscale features are often restricted by limited material variability, lack of control over nanophase filling, challenging transitions to macroscale materials and feature sizes dependent on material delivery equipment.  This work describes a new method to synthesize hierarchically ordered porous nanocomposites by using layer by layer assembly, the sequential adsorption of monoloyers attracted by chemical forces, for controlled introduction of nanocomposites into the void space of highly ordered arrays of uniform microspheres. Feature sizes of the inverted colloidal crystal structure obtained after dissolution of the array are controlled by the diameter of the microsphere, size and annealing time of the array, and number of LBL bilayers deposited on the surface. The method allows for 3D topologies consisting of a wide variety of materials to be created with excellent control over the interfacial connectivity between the inorganic building blocks and a polymer matrix, uniquely high contents of the inorganic phase, and simple transition to macroscale materials. Additionally, due to the morphological control of the technique, uniform composites or gradient structures with feature sizes below the typical dimensions obtained by free-form fabrication, direct write methods, and 3D lithography are possible. Establishing appropriate techniques to produce materials with hierarchical organization of materials involving nano-, micro-, and potentially millimeter scale features with fairly independent control at all levels allows for investigation of structural influences on macroscale material properties and for new practical applications due to the unusual combinations of properties which can be achieved by such controlled assembly of materials and 3D topologies.