Raviteja Kurapati

Adsorption of Polymers at Oil-Water Interfaces

Emulsions are thermodynamically unstable systems. Surfactants are commonly used for stabilising emulsion systems. Amphiphilic polymers can also be used for emulsion stabilisation as well as destabilisation. Polymers are better alternatives to surfactants in terms of strength of attachment to interface and rheological properties. However, the adsorption behaviour of polymers at oil-water interface is complex due to sensitivity of surface activity to large number of factors such as pH of aqueous phase, hydrophobicity of side groups, stereochemistry, presence of ions in the solution and concentration of polymer. Understanding the structure of polymer and interface and influence of factors influencing it are important for design and development of emulsion based systems such as drug formulation, water purification, oil-recovery, etc. I performed atomistic molecular dynamics simulations to investigate the structure of polymer and interface and determined the role of various factors that influence the polymer adsorption.

PhD Work

Phase Behaviour of Nonionic Polymers in Aqueous Solution

Water soluble nonionic polymers, particularly biocompatible ones such as Poly(vinyl alcohol) (PVA) and Poly(ethylene oxide) (PEO), has wide range of industrial applications. Many polymers are not soluble in water because of the hydrophobic backbone. The water solubility of polymer can be improved by attachment of polar groups in the backbone as in the case of PEO or by introducing side groups which can form hydrogen bonds with water as in the case of PVA. The solubility of polymer depends on various factors such as concentration, temperature and molecular weight. I carried atomistic molecular dynamics simulations to investigate the intra-chain, inter-chain and polymer-solvent interactions to assess the solubility of PVA and PEO in aqueous solutions under different conditions.

MSwork

Selection of Solvent for Polymer Processing

The properties of polymers such as polyurethanes not only depend on their chemical structures but also on the processing conditions such as solvents used during the preparation. Further, the rate of evaporation of solvent from polyurethane solution is critical to coating and adhesive application. An understanding of relative strength of interactions between polyurethane segments and polyurethane-solvent is important for selection of solvent. A polyurethane chains consists of hard segments made of diisocyanate and diol groups and soft segments made of polyols or polyethers. I utilized molecular dynamics (MD) simulation techniques to examine two of the most prevalent polyurethanes employed in industry: methylene diphenyl diisocyanate (MDI)-based and toluene diisocyanate (TDI)-based polymers. This investigation was conducted in two solvent environments: dimethylformamide (DMF) and tetrahydrofuran (THF). The study aimed to elucidate the influence of the hard segment structure and solvent type on the conformational properties of polyurethane, the interactions between polyurethane and solvent molecules, as well as the solubility parameter.