Abstract
Vesicle-templated nanocapsules are prepared by polymerization of hydrophobic acrylic monomers and cross-linkers in the hydrophobic interior of self-assembled bilayers. Understanding the mechanism of capsule formation and the influence of synthetic parameters on the structural features and functional performance of nanocapsules is critical for the rational design of functional nanodevices, an emerging trend of application of the nanocapsule platform. This study investigated the relationship between basic parameters of the formulation and synthesis of nanocapsules and structural and functional characteristics of the resulting structures. Variations in the monomer/surfactant ratio, temperature of polymerization, and the molar fraction of the free-radical initiators were investigated with a multipronged approach, including shell thickness measurements using small-angle neutron scattering, evaluation of the structural integrity of nanocapsules with scanning electron microscopy, and determination of the retention of entrapped molecules using absorbance and fluorescence spectroscopy. Surprisingly, the thickness of the shells did not correlate with the monomer/surfactant ratio, supporting the hypothesis of substantial stabilization of the surfactant bilayer with loaded monomers. Decreasing the temperature of polymerization had no effect on the spherical structure of nanocapsules but resulted in progressively lower retention of entrapped molecules, suggesting that a spherical skeleton of nanocapsule forms rapidly, followed by filling the gaps to create the structure without pinholes. Lower content of initiators resulted in slower reactions, outlining the baseline conditions for practical synthetic protocols. Taken together, these findings provide insights into the formation of nanocapsules and offer methods for controlling the properties of nanocapsules in viable synthetic methods.
| Original language | English |
|---|---|
| Pages (from-to) | 13020-13030 |
| Number of pages | 11 |
| Journal | Langmuir |
| Volume | 35 |
| Issue number | 40 |
| DOIs | |
| State | Published - Oct 8 2019 |
Funding
This work was supported by the National Science Foundation (CHE-1709921, CHE-1522525, CHE-1316680, and CHE-1012951) and the University of Connecticut Research Excellence Program. SEM and TEM studies were performed using the facilities in the UConn/FEI Center for Advanced Microscopy and Materials Analysis (CAMMA). Neutron scattering research conducted at the Bio-SANS instrument, a DOE Office of Science, Office of Biological and Environmental Research resource, used resources at the High Flux Isotope Reactor, a DOE Office of Science, Scientific User Facility operated by the Oak Ridge National Laboratory. We acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the neutron research facilities used in this work.