Role of particle clusters on the rheology of magneto-polymer fluids and gels Suarez-Fernandez, William Scionti, Giuseppe García López-Durán, Juan De Dios Zubarev, Andrey López López, Modesto Torcuato Even in absence of cross-linking, at large enough concentration, long polymer strands have a strong influence on the rheology of aqueous systems. In this work, we show that solutions of medium molecular weight (120,000 – 190,000 g/mol) alginate polymer retained a liquid-like behaviour even for concentrations as large as 20 % w/v. On the contrary, solutions of alginate polymer of larger (and also polydisperse) molecular weight (up to 600,000 g/mol) presented a gel-like behaviour already at concentrations of 7 % w/v. We dispersed micron-sized iron particles at a concentration of 5 % v/v in these solutions, which resulted either in stable magnetic fluids or gels, depending on the type of alginate polymer employed (medium or large molecular weight, respectively). These magneto-polymer composites presented a shear-thinning behaviour that allowed injection through a syringe and recovery of the original properties afterwards. More interestingly, application of a magnetic field resulted in the formation of particle clusters elongated along the field direction. The presence of these clusters intensely affected the rheology of the systems, allowing a reversible control of their stiffness. We finally developed theoretical modelling for the prediction of the magnetic-sensitive rheological properties of these magneto-polymer colloids. 2021-04-05T08:00:34Z 2021-04-05T08:00:34Z 2020 info:eu-repo/semantics/article Philosophical Transactions of the Royal Society A 378 (2171), 20190254 http://hdl.handle.net/10481/67766 http://dx.doi.org/10.1098/rsta.2019.0254 eng info:eu-repo/semantics/openAccess