Abstract
We report the aqueous lyotropic mesophase behaviors of protonated amine-based "lipidoids,"a class of synthetic lipid-like molecules that mirrors essential structural features of the multitail bacterial amphiphile lipid A. Small-angle X-ray scattering (SAXS) studies demonstrate that the protonation of the tetra(amine) headgroups of six-tail lipidoids in aqueous HCl, HNO3, H2SO4, and H3PO4 solutions variably drives their self-assembly into lamellar (Lα) and inverse micellar (III) lyotropic liquid crystals (LLCs), depending on acid identity and concentration, amphiphile tail length, and temperature. Lipidoid assemblies formed in H2SO4(aq) exhibit rare inverse body-centered cubic (BCC) and inverse face-centered cubic (FCC) micellar morphologies, the latter of which unexpectedly coexists with zero mean curvature Lα phases. Complementary atomistic molecular dynamics (MD) simulations furnish detailed insights into this unusual self-assembly behavior. The unique aqueous lyotropic mesophase behaviors of ammonium lipidoids originate in their dichotomous ability to adopt both inverse conical and chain-extended molecular conformations depending on the number of counterions and their identity, which lead to coexisting supramolecular assemblies with remarkably different mean interfacial curvatures.
Original language | English (US) |
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Pages (from-to) | 8240-8252 |
Number of pages | 13 |
Journal | Langmuir |
Volume | 36 |
Issue number | 28 |
DOIs | |
State | Published - Jul 21 2020 |
Bibliographical note
Funding Information:This work was financially supported by the National Science Foundation Materials Research Science and Engineering Center (MRSEC) at the University of Wisconsin—Madison under DMR-1121288 and CHE-1807330 (M.K.M.) and made use of core user facilities at the University of Wisconsin—Madison partially supported by DMR-1121288, CHE-9974839, and CHE-1048642. Synchrotron SAXS studies were conducted at Sector 12 of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. M.C.D.C acknowledges the Natural Sciences and Engineering Research Council of Canada for a graduate research fellowship.
Publisher Copyright:
© 2020 American Chemical Society.