(600g) Self Assembly of Nano-Composite Tectons (NCTs) As a Response to Thermal and Mechanical Stimuli

Nano-composite tectons (NCTs)—hybrid building blocks made from inorganic nanoparticles functionalized with organic ligands—are gaining attention as versatile components for designing functional materials. Their tunable interactions and modular architecture make them ideal for applications in photonic crystals, catalysis, and chemical sensing platforms. Understanding their self-assembly into ordered, continuous structures under practical processing conditions is essential to designing novel composite materials. A key question is how to reliably control both the local arrangement (e.g., crystallinity) and the long-range ordering of these materials.

In this work, we present an integrated experimental and computational effort to investigate the self-assembly of NCTs into hierarchical structures under controlled thermal and mechanical processing. A dilute solution of NCTs is subjected to two types of processing – 1) thermal annealing and 2) mechanical deformation (sintering). During thermal annealing, the system is slowly cooled from an initially disordered state. The cooling rate is carefully tuned to allow for sufficient relaxation and ordering. We study the interplay between the cooling rate and particle interactions in crystal formation. The annealed systems are then subjected to mechanical deformation via isotropic compression to mimic the sintering process that results in merging of the individual crystals and enhancement in overall system connectivity.

We analyze the resulting structures using a combination of bond-orientational order parameters, local density metrics, and grain boundary mapping to quantify crystallinity, defect distribution, and domain morphology. We find that slow cooling leads to the spontaneous emergence of well-ordered crystalline domains that display long-range order. Applying mechanical deformation to preassembled crystals causes particles at domain boundaries to fuse. This process improves mechanical integrity and promotes continuous networks. However, it also introduces grain boundaries, dislocations, and other defects where domains misalign or strain accumulates. Our results highlight the role of both thermal and mechanical factors in determining the final architecture and structural integrity of the material. These findings provide key insights into the design principles for directing self-assembly and sintering in hybrid colloidal systems, paving the way for tailored nanoscale materials with hierarchical order and enhanced functionality.