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Mesoporous organohydrogels from thermogelling photocrosslinkable nanoemulsions

Nature Materials volume 11, pages 344–352 (2012)Cite this article

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Abstract

We report the formation of mesoporous organohydrogels from oil-in-water nanoemulsions containing an end-functionalized oligomeric gelator in the aqueous phase. The nanoemulsions exhibit an abrupt thermoreversible transition from a low-viscosity liquid to a fractal-like colloidal gel of droplets with mesoscale porosity and solid-like viscoelasticity with moduli approaching 100 kPa, possibly the highest reported for an emulsion-based system. We hypothesize that gelation is brought about by temperature-induced interdroplet bridging of the gelator, as shown by its dependence on the gelator chemistry. The use of photocrosslinkable gelators enables the freezing of the nanoemulsion’s microstructure into a soft hydrogel nanocomposite containing a large fraction of dispersed liquid hydrophobic compartments, and we show its use in the encapsulation and release of lipophilic biomolecules. The tunable structural, mechanical and optical properties of these organohydrogels make them a robust material platform suitable for a wide range of applications.

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Figure 1: Thermoreversible formation of a nanoemulsion organohydrogel.
Figure 2: Microstructural characterization of the nanoemulsion organohydrogel described in Fig. 1.
Figure 3: Control of organohydrogel properties through variation of PEG end-functional chemistry.
Figure 4: Organohydrogel formation occurs over a wide range of nanoemulsion formulation conditions.
Figure 5: The drop-size dependence of organohydrogel rheology indicates a gel–paste transition.
Figure 6: Photocrosslinking of organohydrogels allows for ‘freezing’ of the nanoemulsion microstructure, yielding soft composites with unique properties.

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Acknowledgements

We acknowledge financial support from the Novartis-MIT Center for Continuous Manufacturing, as well as the support of the National Institute of Standards and Technology, US Department of Commerce, in providing the neutron research facilities used in this work, supported in part by the National Science Foundation under agreement DMR-0454672. P.S.D. and H.Z.A. acknowledge support from the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the US Army Research Office. The content of the information does not necessarily reflect the position or the policy of the government, and no official endorsement should be inferred. We thank G. McKinley for the use of rheometry equipment in this work.

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  1. Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

    Matthew E. Helgeson, Shannon E. Moran, Harry Z. An & Patrick S. Doyle

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  1. Matthew E. Helgeson
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Contributions

M.E.H. and P.S.D. designed the experiments. M.E.H. and S.E.M. prepared the nanoemulsions and carried out rheology, neutron scattering and photopolymerization experiments. M.E.H. carried out analysis of SANS/USANS data. M.E.H. and H.Z.A. carried out flow lithography and triggered release studies. M.E.H., S.E.M., H.Z.A. and P.S.D. prepared the manuscript.

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Correspondence to Patrick S. Doyle.

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Helgeson, M., Moran, S., An, H. et al. Mesoporous organohydrogels from thermogelling photocrosslinkable nanoemulsions. Nature Mater 11, 344–352 (2012). https://doi.org/10.1038/nmat3248

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