%0 Journal Article
%A Morse, Andrew
J.
%A Madsen, Jeppe
%A Growney, David J.
%A Armes, Steven P.
%A Mills, Peter
%A Swart, Ron
%D 2014
%T Microgel Colloidosomes Based on pH-Responsive Poly(tert-butylaminoethyl methacrylate) Latexes
%U https://acs.figshare.com/articles/journal_contribution/Microgel_Colloidosomes_Based_on_pH_Responsive_Poly_i_tert_i_butylaminoethyl_methacrylate_Latexes/2241136
%R 10.1021/la5033674.s001
%2 https://acs.figshare.com/ndownloader/files/3877075
%K PEGMA
%K resistance
%K emulsion
%K removal
%K laser diffraction studies
%K copolymer latex particles
%K mol
%K pH 10
%K glycol
%K methacrylate
%K 1 H NMR spectroscopy
%K Such PTBAEMA colloidosomes
%K cationic microgel form
%K latexe
%K ethanol
%K presence
%K DVB
%K glass transition temperatures
%K amine
%K fluorescence microscopy studies
%K copolymerization
%K TBAEMA comonomer contents
%K oil droplet size
%K surface
%K Pickering
%K PTBAEMA latex particles
%K phase
%K electron microscopy images
%X Emulsion copolymerization of 2-(tert-butylamino)ethyl
methacrylate (TBAEMA) with divinylbenzene (DVB) cross-linker in the
presence of monomethoxy-capped poly(ethylene glycol) methacrylate
(PEGMA) at 70 °C afforded sterically stabilized poly[2-(tert-butylamino)ethyl methacrylate] (PTBAEMA) latexes at
10% solids at pH 9. Such particles proved to be an effective Pickering
emulsifier at pH 10 for both n-dodecane and n-hexane. 1H NMR spectroscopy was used to follow
the model reaction between the secondary amine of the TBAEMA monomer
and the isocyanate groups of tolylene 2,4-diisocyanate-terminated
poly(propylene glycol) (PPG-TDI). Cross-linking the PTBAEMA latex
particles adsorbed at the n-dodecane/water interface
using this oil-soluble PPG-TDI cross-linker at around 0 oC led to robust colloidosomes that survived an acid challenge. This
resistance to demulsification was confirmed via laser diffraction
studies following an in situ switch from pH 10 to 3, since no change
was observed in either the oil droplet size or concentration (compared
to non-cross-linked PTBAEMA-stabilized Pickering emulsions). Such
PTBAEMA colloidosomes survived removal of the internal oil phase on
washing with excess ethanol. However, because ethanol is a good solvent
for the PTBAEMA chains, imaging the ethanol-treated colloidosomes
via electron microscopy proved rather problematic due to partial film
formation. Therefore, a series of TBAEMA/styrene copolymer latexes
(comprising 10, 30, 50, or 60 mol % styrene) were prepared via emulsion
copolymerization at 70 °C in the presence of DVB and PEGMA. The
higher glass transition temperatures exhibited by these copolymer
particles (and their greater resistance to ethanol swelling) enabled
better-quality electron microscopy images to be obtained. The presence
of nitrogen atoms at the surface of these copolymer latex particles
was confirmed via X-ray photoelectron spectroscopy studies; these
secondary amine groups allow covalent cross-linking via PPG-TDI when
adsorbed at the surface of n-dodecane droplets at
TBAEMA comonomer contents as low as 40 mol %. After removal of the n-hexane oil phase by evaporation, fluorescence microscopy
studies indicate that these colloidosomes undergo collapse in their
latex form at pH 10 but regain their original spherical morphology
in their cationic microgel form at pH 3.5.
%I ACS Publications