Nanoparticles from a controlled polymerization process

Abstract

Free-radical retrograde precipitation polymerization process in the past has shown excellent control characteristics over reaction rate, molecular weight, and in the entrapment of live radicals for the generation of block copolymers. The same principle has now been extended to study the reaction confinement to a nanoscale region. Nanosized polymer particles have been reported to form from block copolymers, conventional precipitation polymerization methods, or through emulsion polymerization approaches. In this work, we present a new method of generating nanosized polymer particles by polymerizing the monomer in an environment that precipitates the polymer above the lower critical solution temperature. The nanoparticles have been characterized by both tapping-mode atomic force microscopy observations and in situ synchrotron time-resolved small-angle X-ray scattering analysis. The results from both the techniques showed the formation of nanoparticles in the size range

Free‐radical retrograde‐precipitation copolymerization of vinyl acetate and acrylic acid

“…Further, if a significant proportion of AA is added to the reactor while initiation is taking place so it can be incorporated into most initiated chains until all initiator molecules are exhausted, the longevity of the polymer radicals makes it possible to continue propagation with VA monomer to produce tapered block copolymers. This is possible due to the novel features shown by the FRRPP process as described in previous work4, 6 including long lived free radicals and evidence of polymerization control.…”

“…Becasue the reaction rate is controlled, the polymer‐rich domain growth has also been found to be under good control if domain interaction is minimized 6. In a well‐mixed vessel, some nanometer‐sized polymer particles have been obtained when a crosslinker was included with the reaction recipe.…”

Synthesis of nanosized poly(ethyl acrylate) particles via differential emulsion polymerization

“…Nanosized polymer particles have attracted great interest because of their attractive properties arising from the dimension effect and the surface/volume ratio effect. They have potential applications in various fields, such as catalysts, colorants, pesticides, lubricants, electrophotography, biosensors, and microelectromechanical systems 1. The common methods for preparing nanosized polymers include molecular assembly, template chemistry, dendrimer polymerization, mechanical pulverization, and microemulsion polymerization, among which microemulsion polymerization is the most widely used method 2–5.…”

In situ fabrication of thermoreversible microgels

“…In a quiescent fluid though, these growing polymer domains would have to actually grow into each other to agglomerate, since agglomeration is usually facilitated by mixing. Therefore, the isolated growing polymer globules can be preserved in a quiescent system for longer reaction times than in a well-mnixed reactor [21]. Higher reaction temperatures would also slow down the growth rate of polymer globules as the free radical chain ends get trapped inside the globules during precipitation.…”

“…The exothermic chain polymerization reaction in such systems is inherently controlled by balancing itself against the polymer-solvent equilibrium thermodynamics. The reaction can, therefore, directly lead to the formation of polymeric nanoparticles [21] and spatially limited chain growth, if the initiation is similarly defined in space. Figure 1 illustrates the methodology of the synchrotronradiation-induced spatially controlled polymer synthesis.…”