Hunter, S.J. orcid.org/0000-0002-9280-1969, Penfold, N.J.W., Chan, D.H. et al. (2 more authors) (2020) How do charged end-groups on the steric stabilizer block influence the formation and long-term stability of Pickering nanoemulsions prepared using sterically stabilized diblock copolymer nanoparticles? Langmuir, 36 (3). pp. 769-780. ISSN 0743-7463
Abstract
Reversible addition–fragmentation chain transfer (RAFT) solution polymerization is used to prepare well-defined poly(glycerol monomethacrylate) (PGMA) chains bearing carboxylic acid, tertiary amine, or neutral end-groups. Each of these PGMA precursors was then chain-extended in turn via RAFT aqueous emulsion polymerization of 2,2,2-trifluoroethyl methacrylate to form spherical nanoparticles as confirmed by transmission electron microscopy (TEM) analysis. Dynamic light scattering studies indicated an intensity-average diameter of approximately 25 nm. Aqueous electrophoresis measurements confirmed that the amine-functional nanoparticles became cationic at low pH owing to end-group protonation. In contrast, carboxylic acid-functional nanoparticles became appreciably anionic at pH 10 owing to end-group ionization. Finally, nanoparticles bearing neutral end-groups exhibited zeta potentials close to zero over a range of solution pH. High-shear homogenization of n-dodecane in the presence of such sterically stabilized nanoparticles led to the formation of oil-in-water Pickering macroemulsions with volume-average diameters of 20–30 μm. High-pressure microfluidization was then used to prepare the three corresponding Pickering nanoemulsions. Each Pickering nanoemulsion was characterized by analytical centrifugation and TEM studies of the dried nanoemulsion droplets confirmed their original nanoparticle superstructure. The nanoparticle adsorption efficiency at the oil–water interface was assessed by gel permeation chromatography (using a UV detector) for each nanoparticle type at both pH 3 and 7. Nanoparticles with charged end-groups exhibited relatively low adsorption efficiency, whereas up to 90% of the neutral nanoparticles were adsorbed onto the oil droplets. This observation was supported by small-angle X-ray scattering experiments, which indicated that the packing efficiency of neutral nanoparticles around oil droplets was higher than that of nanoparticles bearing charged end-groups. Analytical centrifugation was used to evaluate the colloidal stability of the aged Pickering nanoemulsions. Pickering nanoemulsions stabilized with nanoparticles bearing charged end-groups proved to be significantly less stable than those prepared using neutral end-groups.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2020 American Chemical Society. This is an author-produced version of a paper subsequently published in Langmuir. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
|
Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Funding Information: | Funder Grant number Engineering and Physical Sciences Research Council EP/L016281/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 19 Mar 2020 15:31 |
Last Modified: | 03 Jan 2021 01:38 |
Status: | Published |
Publisher: | American Chemical Society (ACS) |
Refereed: | Yes |
Identification Number: | 10.1021/acs.langmuir.9b03389 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:158562 |