Start
Apr 13, 2018 - 16:00
End
Apr 13, 2018 - 17:00
Venue
Room No. 240 first floor next to Chem. Engg. deptl. office
Event Type
Speaker
Dr. Guruswamy Kumaraswamy Polymer Science and Engineering Division CSIR-National Chemical Laboratory Pune INDIA.
Title
Using Ice-Templating to Assemble Colloids into Macroporous Objects and into Chains
Abstract: Macroscopic objects formed from particle assemblies are typically brittle precluding their use in several applications. Some years ago we demonstrated that ice-templating an aqueous dispersion of rigid colloidal particles and polymer and crosslinking this polymer in the frozen state results in the formation of remarkably flexible colloidal assemblies. Centimeter-scale monoliths prepared in this manner recover elastically after compression to 10% of their original size. These mechanical properties are a consequence of a unique microstructure: polymers crosslinked in the frozen state form a mesh around particles in the pore walls. Subtle differences in the protocol for assembling nanoparticles play a critical role in determining their properties. Macroporous monoliths that are chemically “identical” but that are prepared using small variations in the ice templating protocol exhibit qualitatively different mechanical behaviour. We demonstrate that the preparation protocol modulates the spatial variation in crosslink density. Elastic scaffolds have a uniform distribution of crosslinks while scaffolds that have the same average crosslink density but spatially heterogeneous crosslinks exhibit brittle failure. Finally I show that we can use the same protocol to form flexible linear chain-like assemblies. These colloidal analogs of polymer chains represent a convenient model system to study polymer physics. I will present results on the dynamics of active colloidal chains prepared using this protocol.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. (10.1021/acs.langmuir.7b04120)
2. Biswas B.; Manna R.; Laskar A.; Kumar P. B. S.; Adhikari R.; Kumaraswamy G. Linking catalyst-coated isotropic colloids into "active" flexible chains enhances their diffusivity. ACS Nano 2017 11 10025–10031.
3. Karthika S.; 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.
4. Biswas B.; Choudhury C. K. Kumaraswamy G. Colloidal assembly through ice-templating. Faraday Discussions 2016 186 61-76.
5. 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.
Bio-sketch: Guruswamy Kumaraswamy received a BTech in Chemical Engineering from IITB in 1994 followed by an MS (1996) and PhD (2000) in Chemical Engineering from the California Institute of Technology. He spent a year as a VW Postdoctoral Fellow at the Max Planck Institute for Colloids and Interfaces. In 2001 he joined CSIR-National Chemical Laboratory in Pune as a scientist and has been there since. Guruswamy’s work focuses on controlling structure and investigating structure-property relations in soft matter systems. These systems range from polymers to surfactants and lipids and colloids. He collaborates extensively with industry and has worked with companies in India and abroad in the area of polymers healthcare personal care waste valorization etc. He is also passionate about science outreach to school students and in the last ten years he has been associated with a volunteer group called the Exciting Science Group.