He first introduced the notion of non-Newtonian fluids comprising polymer solutions, polymer methods, suspension, biological fluids, etc. He described many bizarre flow phenomena that these fluids exhibited such as rod climbing, die swelling, inverse siphon, etc. He introduced the notion of a viscous fluid, a visco-elastic fluid and an elastic solid. He then traced the way the foundations of rheology were laid by using a phenomenological approach and then through molecular models. Non-Newtonian fluid mechanics had advanced sufficiently today to explain the flow behavior in many complex situations.

 However, under certain conditions the fibres so formed did not redissolve even when boiled! The phenomenon was explained by demonstrating that deformation of polymer chains induces effective hydrophobicity in the stretched polymer chains resulting in the formation of strong cooperative hydrogen bonding between the polymer chains. The LFHB model for hydrodynamically induced hydrophobicity was able to explain the phenomenon of non-dissolving  fibres.He recalled the observations by Vollrath and Night in a paper in Nature (2001), while studying the formation of silk fibres that ‘That high stress forces generated during this stage of processing probably bring the dope molecules into alignment and into a more extended conformation, so that they are able to join together with hydrogen conformation of final thread. As the silk protein molecules aggregate and crystallize, they will become more hydrophobic, which should induce phase separation and hence the loss of water from the surface of solidifying thread’. He showed that in the year 2000 itslef, Lele, Joshi & Mashelkar had demonstrated this physical phenomena through a quantitative LFHB Model. Dr Mashelkar then referred to some of the recent experimental work on in-situ flow induced phase separation in silk-dope that was being carried out at NCL. The hydrodynamic analysis was strongly suggestive of a stratified flow with the pre-orientation of the liquid crystalline dope leading to a plug core flow with a solvent layer at the wall. Pursuing this theme further, Mashelkar referred to the phenomenon of lower critical solution temperature in certain gels, which could not be explained by the simple Flory theory of swollen networks. Specific hydrogen bonding interactions had to be incorporated.He then described the development of LFHB models by Dr Lele and Mashelkar during the last six to seven years, which had brought out the role of the subtle balance of hydrophobicity and hydrophilicity in controlling the volume transition. He then described the phenomena of macroscopic self-organization in gels and also the self-healing in gels that was discovered for the first time in his group in NCL and the critical role the energetic interactions played in these phenomena. Dr Mashelkar’s final message as enumerated in one of his viewgraphs, succinctly summarized the main theme of his lecture: Look at the experimental points that do not fit the prediction curve Look at the failed experiments Chase anomalies and discontinuities Next conceptual breakthrough may lie there!
Dr Mashelkar ended his lecture with a quote from Richard Feynman ‘The difficulty with science is often not with new ideas, but in escaping the old ones. A certain amount of irreverence is essential for creative pursuit of science’. The challenge, he felt, was to create these ‘irreverent’ Indian scientists!

However, in the simplest of flows, there are still surprises. For example, in the viscoelastic flow part a sphere, there were anomalies, which had remained unresolved for decades. These included time dependent terminal velocities, creation of a ‘virtual hole’ in a fluid resulting in cross migration of a sphere and abnormally long restoration times that were an order of a magnitude higher than the relaxation times of the fluid. The rheologists were perplexed about these effects, some calling them ‘extravagant transient effects’. He quoted the famous scientist Walters and his colleagues showing their desperation by saying ‘Simulation for the UCM & Oldroyd B Models (using acceptable values of relaxation times) have no hope of predicting observed transient response. Indeed explaining time scale which is compatible to the chain relaxation time …….
A mirorheological model is needed’. It was precisely this challenge that was met by Dr Mashelkar and his associate Dr Lele in late nineties by developing Energetically Crosslinked Transient Network (ECTN) models. They recognized that due to hydrogen bonding, there were energetic networks that were formed, whose characteristics were very different from the physical entanglements on which the current models were based. An essential feature was that the formation of physical entanglements were non-specific, whereas the formation of an energetic network required specificity and cooperative network mobility. Similarly cooperative effects were significant during zipping and unzipping of ladder like structures. ECTN models showed as to how several so called ‘bizarre’ flow phenomena could be now explained.Dr Mashelkar also provided proton spin-lattice and spin-spin relaxation data obtained through carefully conducted rheo-NMR experiments to back up the physics implicit in his ECTN models Dr Mashelkar also took up another anomaly, which had remained unexplained for decades. When flow induced phase separation occurred in polymeric systems, it was invariably reversible.