Rheological Control Of Microemulsions Is Possible By Admixture Of End–Capped Multi–Arm Polymers Of Different Functionality – A Study Of Structure And Dynamics
July 21-24, 2019
For many applications the interesting properties of microemulsion, which are thermodynamically stable mixture of oil and water facilitated by the presence of a surfactant, are highly interesting. However, for many of these potential applications a much higher viscosity or even gelation would be asked for. Accordingly, mixtures of telechelic polymers and microemulsions are interesting systems from a practical point of view as by the addition of the polymer one is able to exert rheological control over a rather wide range. Furthermore they are model systems of networks where concentration of nodes and connectivity can be tuned separately, which allows for a systematic understanding of the control of the rheological properties of these materials.
In our investigation we employed end-capped multi-arm polymers for the bridging of the microemulsion droplets which leads to network formation. For that purpose we employed tailor-made bridging amphiphilic polymers with multiple linkers, which were synthesized by the RAFT procedure with poly(N,N-dimethylacrylamide) (PDMA) as hydrophilic central block. This synthesis allows to control the number of arms (functionality), the length of the hydrophilic group (maximum length for connection) and of the hydrophobic chain (stickiness). We employed various multiply bridging polymers with 2, 3, or 4 arms (see figure) and investigated their effect on structure and dynamics of nonionic O/W microemulsion droplets with radii in the range of 2.5-7 nm.
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Michael Gradzielski, Paula Malo de Molina, and Christoph Herfurth, "Rheological Control Of Microemulsions Is Possible By Admixture Of End–Capped Multi–Arm Polymers Of Different Functionality – A Study Of Structure And Dynamics" in "Colloidal, Macromolecular and Biological Gels II", Samiul Amin, Manhattan College, USA Saad Khan, North Carolina State University, USA Srini Raghavan, University of Maryland College Park, USA Eds, ECI Symposium Series, (2019). https://dc.engconfintl.org/cmb_gels_ii/10