In this lecture, I will discuss several recently developed strategies for fabrication of porous and structured composites in various areas of materials science which allows fine tuning of their properties. In my group, we formulated a novel two-component hydrogel system consisting of food grade biopolymers, Agar and methylcellulose (MC), with a tailorable storage modulus over a wide temperature range due to overlapping sol-gel transitions. The addition of MC to agar showed an increase in the hydrogel storage modulus both below and above the MC gelling point. Above the melting point of Agar, the mixed hydrogel was still elastic with rheological properties dominated by MC. The mixed Agar-MC hydrogels were very stable and did not melt even upon heating above 150 °C. We demonstrated the application of this ultra-melt resistant hydrogel system for calorie reduction in bakery products and personal care formulations. We also recently developed hierarchically porous light weight gypsum or cement porous composites by using a combination of the hydrogel slurry templating and viscous trapping techniques. This allowed us to control the ratio of micro-to-nanopores and tailor the composite specific mechanical properties. We also studied the thermal conductivity, sound absorption and transmission loss of hierarchically porous cement composites produced using a dual hydrogel templating technique. In another example, we fabricated materials from capillary structured suspensions from hydrophilic calcium carbonate particles suspended in a polar continuous media and connected by capillary bridges formed of a minute amounts of an immiscible secondary oil phase. The capillary structuring was made possible through local in-situ hydrophobization of the calcium carbonate particles dispersed in the polar liquid media by adding very small amounts of hydrophobizing agent in the oil phase. I will also discuss the fabrication of stimulus responsive capillary suspensions which can find application in structuring of pharmaceutical and cosmetic formulations as well as home care products.
Vesselin Paunov is a Professor of Physical Chemistry and Advanced Materials at the Department of Chemistry and Biochemistry at the University of Hull, UK. He received his Ph.D. in Physical Chemistry from the University of Sofia, Bulgaria, where he studied the lateral capillary interactions between colloid particles adsorbed at liquid surfaces. During his Ph.D. studies, he also specialized at the Chemical Engineering Department of the University of Partas, Greece, and at the Institute of Fluid Mechanics at the University of Erlangen, Germany. In 1997 he was awarded NATO/Royal Society Postdoctoral Fellowship at the Department of Chemistry of the University of Hull, UK. In 1998, he moved to the USA as a Post-Doctoral Fellow at the Chemical Engineering Department of the University of Delaware. In 2000 he was appointed as a lecturer in Physical Chemistry at the University of Hull, UK and was promoted to professor in 2013. Prof Paunov does highly interdisciplinary research in the areas of colloids, nanoscience and biomaterials. He has published over 160 scientific papers in international journals and is a co-inventor of 13 patents (google scholar). Prof Paunov has given over 120 invited and conference presentations. His present research interests include formulation science, smart materials, hydrogels, capillary suspensions, microencapsulation, stimulus triggered release of actives, tissue engineering, whole cell biosensors, cell bioimprinting and antimicrobial nanotechnologies (www.paunovgroup.org).