One-Step Preparation of
Uniform Cane-Ball Shaped Water-Swellable
Microgels Containing Poly(<i>N</i>-vinyl formamide)
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Abstract
In this study we report the preparation of a new family
of core–shell
microgels that are water-swellable and have a morphology that is controllable
by particle composition. Here, nearly monodisperse core–shell
PNVF-<i>x</i>GMA [poly(<i>N</i>-vinylformamide-<i>co</i>-glycidyl methacrylate)] particles (where <i>x</i> is the weight fraction of GMA used) were prepared via nonaqueous
dispersion (NAD) polymerization in one step. The shells were PGMA-rich
and were cross-linked by reaction of epoxide groups (from GMA) with
amide groups (from NVF). The core of the particles was PNVF-rich.
A bifunctional cross-linking monomer was not required to prepare these
new microgels. The particles had a remarkable “cane-ball”-like
morphology with interconnected ridges, and this could be controlled
by the value for <i>x</i>. The particle size was tunable
over the range 0.8–1.8 μm. Alkaline hydrolysis was used
to hydrolyze the PNVF segments to poly(vinylamine), PVAM. The high
swelling pressure of the cationic cores caused shell fragmentation
and release of some of the core polymer when the hydrolyzed particles
were dispersed in pure water. The extent to which this occurred was
controllable by <i>x</i>. Remarkably, the PGMA-rich shells
could be detached from the hydrolyzed particles by dispersion in water
followed by drying. The hydrolyzed PNVF-0.4GMA particles contained
both positively and negatively charged regions and the dispersions
appeared to exhibit charge-patch aggregation at low ionic strengths.
The new cross-linking strategy used here to prepare the PNVF-<i>x</i>GMA particles should be generally applicable for amide-containing
monomers and may enable the preparation of a range of new water-swellable
microgels