Physics

Prof. Guruswamy Kumaraswamy
CSIR-National Chemical Laboratory, Pune

Abstract :

Composite materials that incorporate inorganic fillers into polymers combine the mechanical attributes of both materials. The fillers increase the rigidity of the composites and the polymers endow it with toughness. The microstructure, viz. the specific spatial arrangement of the particles and polymer in the composite is critical in determining its mechanical properties. For example the remarkable toughness of nacre is attributed to the precise layered arrangement with protein interspersed between calcium carbonate plate-like aragonite crystals. We show that a simple preparation protocol for composite foams, ice-templating, results in the formation of remarkably elastic materials. These materials are primarily inorganic, comprised of over 90% by weight of inorganic particles, and yet can recover from compression to a tenth of their original size. Macroscopic objects formed from particle assemblies are typically brittle – therefore, the behaviour of the ice-templated composite foams is highly unusual. We demonstrate that the elasticity of these foams arises from the microstructure developed by the preparation process. Freezing the composites during ice templating and crosslinking in the frozen state results in the formation of a mesh-like network around the particles. Subtle differences in the preparation protocol play a critical role in determining their properties. We employ a variety of experimental techniques to demonstrate that the preparation protocol modulates the spatial variation in crosslink density.

References:

1. Suresh, K.; Chulliyil, R.; Sharma, D. K.; Ketan; Kumar, V. R.; Chowdhury, A.; Kumaraswamy, G. Single particle tracking to probe the local environment in crosslinked colloidal assemblies Langmuir 2018, 34, 4603–4613.
2. Suresh, K.; Patil, S.; Rajamohanan, P. R.; Kumaraswamy, G. The Template Determines Elastic Recovery or Plastic Failure of Chemically Identical Nanoparticle Assemblies. Langmuir  2016, 32, 11623–11630.
3. Rajamanickam, R.; Kumari, S.; Kumar, D.; Ghosh, S.; Kim, J. C.; Tae, G.; Sengupta, S.; Kumaraswamy, G. Soft colloidal scaffolds capable of elastic recovery after large compressive strains. Chem. Mater. 2014, 26, 5161-5168.