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Polymer architecture dictates thermoreversible gelation in engineered emulsions stabilised with branched copolymer surfactants

Research output: Contribution to journalArticlepeer-review

A. Rajbanshi, M. A. Da Silva, D. Murnane, L. Porcar, C. A. Dreiss, M. T. Cook

Original languageEnglish
Pages (from-to)5730-5744
Number of pages15
JournalPolymer Chemistry
Issue number40
Early online date26 Sep 2022
Accepted/In press9 Sep 2022
E-pub ahead of print26 Sep 2022
Published26 Sep 2022

Bibliographical note

Funding Information: This work benefited from the use of the SasView application, originally developed under NSF award DMR-0520547. SasView also contains code developed with funding from the European Union's Horizon 2020 research and innovation programme under the SINE2020 project, grant agreement No. 654000. The authors thank the Institut Laue Langevin for the provision of neutron beam time on D22 instrument (10.5291/ILL-DATA.9-11-2028). The Engineering and Physical Sciences Research Council (EP/T00813X/1) and Royal Society of Chemistry (RF17-9915) are acknowledged for funding the research. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising. Data is available on reasonable request to the authors. Publisher Copyright: © 2022 The Royal Society of Chemistry.


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The generation of materials that switch from a liquid to gel state upon warming can enable new healthcare technologies with improved functionality, such as in situ gel-forming materials for drug delivery to topical or parenteral sites. The majority of these materials are aqueous polymer solutions, which then suffer from an inability to solubilise hydrophobic drugs. This study investigates the generation of thermoresponsive “engineered emulsions” which are low-viscosity emulsions at low temperature and switch to a gel state upon warming. This is achieved by the synthesis of novel branched copolymer surfactants (BCS) containing di(ethylene glycol) methyl ether methacrylate (DEGMA) as a thermoresponsive component giving a lower critical solution temperature (LCST). The copolymers were employed as emulsifiers to prepare 1 : 1 dodecane:water emulsion systems. The effect of polymer architecture is shown to be intimately linked to the rheology of these systems, where branching, elevation of molecular weight, and the presence of hydrophobic end groups is demonstrated to be commensurate with gel formation upon heating. Mechanisms of gel formation were probed by small-angle neutron scattering, which demonstrated that the branched copolymer surfactants formed oblate ellipsoids in solution that grew anisotropically with temperature, forming larger disk-like nanoparticles. The formation of these elongated particles leads to thickening of the emulsions, whilst connectivity of the aggregates and BCS at the oil–water interface is required for gel formation to occur. Overall, the study provides design principles for this novel class of thermoresponsive material with great potential in healthcare, cosmetic, and energy applications.

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