Alzhrani, Attyah (2011) Fabrication of anisotropic polymer colloid particles. PhD thesis, University of Warwick.

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Abstract

The fabrication of complex colloidal particles with anisotropic "patchy" e.g. Januslike,
morphology will be studied. Known approaches towards "Janus particles" focus
mostly on the micron-sized domain, with common fabrication routes based on
monolayer modification or microfluidic production (restricts scale-up). We operate
in the submicron regime (typically 100-500 nm) and use scalable emulsion
polymerization strategies, in combination with entropic phase separation of swollen
cross-linked latex particles and living radical polymerization, i.e. SET-LRP, to
prepare our "patchy" amphiphilic particles.
In this research, various Cross-linked densities (typically from 1 - 8wt%)
poly(styrene) latexes (typically 100-500 nm) functionalized with tert-bromine
functional groups, by batch or shot addition of (2-methacryloxyethyl -2-
bromoisobutyrate) made via soap-free emulsion polymerization used as the precursor
particles.
Two synthetic pathways were investigated to make the targeted hairy Janus Particles.
Approach one: in which we carried out the domain formation step prior to the
fabrication of the polymer brushes, We found out that the effective synthetic way to
make Janus hairy dumbbell particles in a reproducible manner is to start the
synthesis with light cross-linked density of (1.9 to 3.0 wt% DVB) precursor
poly(styrene) latex particles (150-250 nm diameter) made by shot addition method.
The direct entropic phase separation from these latex particles leads to the formation
of only one new domain with dumbbell shape morphology, when the swelling ratio
used between monomer and latex is between 2.0 and 4.0, and with low DVB concentration in the swelling monomer (between 0.15-1.0wt%) using AIBN as
initiator.
Formation of hydrophilic polymer brushes by SET-LRP resulted in targeted hairy
Janus particles with sub-micrometer diameter, in a reproducible manner. The length
of the polymer brushes can be controlled by addition of water soluble ATRP initiator
to produce shorter polymer brushes. The rate of SET-LRP was ultrafast and the rate
can be reduced by addition of deactivator CuBr2.
The second approach: water-soluble polymer brushes were grafted onto the surface
of latex particles by SET-LRP. These “hairy” cross-linked colloids were swollen
with additional monomers and initiator. Elevation of temperature causes entropic
phase separation inducing new domains, which were polymerized. This approach
leads to mainly popcorn and raspberry particles with some limited cases that are able
to make hairy Janus Particles with non reproducible manner.
The obtained complex particles show some interesting application such as a
stabilization agent for Carbon Nanotubes (CNTs) in aqueous medium, Pickering
emulsion stabilizer, and they self assembled upon addition of dilute electrolyte
solution.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Polymer colloids, Anisotropy
Official Date:	September 2011
Dates:	Date Event September 2011 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Bon, Stefan Antonius Franciscus
Sponsors:	Sharikah al-Saʻūdīyah lil-Ṣināʻāt al-Asāsīyah
Extent:	xiii, 354 leaves : ill., charts
Language:	eng

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