Exploration of the Mechanism for Self-Emulsion Polymerization
of Amphiphilic Vinylpyridine
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Abstract
A rare
self-assembly behavior is observed in a hydrophilic monomer (4-vinylpyridine)
(4VP) when polymerized in water with a hydrophilic initiator that
results in the production of monodisperse polymeric nanoparticles
in a single step. This behavior mimics the behavior obtained with
the more commonly reported amphiphilic block copolymers. The synthesis
and self-assembly of homopolymer nanoparticle from 4VP without the
use of any cross-linker, stabilizing agent, surfactant, or polymeric
emulsifier are described along with fundamental aspects of the mechanism
of this polymerization. This facile and robust procedure enabled the
production of highly monodisperse P4VP nanoparticle with a tunable
size ranging from 80 to 445 nm. For the first time, we have investigated
the growth mechanism of these polymeric nanoparticles to clarify the
mechanism of polymeric nanoparticle formation. This work also provides
direct visible evidence through transmission electron microscopy (TEM)
images at the nanometer scale, which helps in obtaining a better understanding
of the mechanism of self-assembly. The effect of temperature on the
size of the polymeric nanoparticles was also examined along with the
effect of initiator, monomer, and solvent concentrations. We therefore
report a versatile and scalable process for the production of monodisperse
polymeric nanoparticles, which we call self-emulsion polymerization
(SEP)