Flash nanoprecipitation of polystyrene nanoparticles
In the article Flash nanoprecipitation of polystyrene nanoparticles, Priestly et al. discuss the benefits of utilizing the nanoprecipitation method to generate polymer nanoparticles relative to other methods. In the nanoprecipitation method, nanoparticles are precipitated from polymer chains in solution as a result of displacing a solvent with a non-solvent. The advantages include independent control of size and molecular weight that is achievable due to bulk polymer is used as a precursor, fast processing time, low energy consumption, and high reproducibility. Some disadvantages include broad size distributions for nanoparticle samples with a diameter greater than several hundred nanometers and low mass fractions of nanoparticles. However, Priestly et al. attempt to correct these disadvantages by using a particular nanoprecipitation method called flash nanoprecipitation (FNP). This achieves rapid solvent displacement by means of high intensity mixing geometries in a cavity fed by two solvent streams. By using this method, the size of nanoparticles is more easily controlled. Nanoparticles with narrow polydispersity with diameters less than 150nm are created. This in effect corrects the previous disadvantages of using nanoprecipitation in terms of low mass fractions as they are controlled for by changing styrene concentration and/or ammonium persulfate concentration in reactor. However, FNP still has the challenge of maintaining low polydispersity, particles or molecules of varied sizes in a mixture, for larger particles.
Fragility and glass transition temperature of polymer nanoparticles
In the article Fragility and glass transition temperature of polymer confined under isobaric and isochoric conditions, Priestly and Zhang measure the dynamic fragility index and the Tg (glass transitioning temperature) of confined poly(4-methylstyrene) under isobaric (constant pressure) and isochoric (constant volume). They found that isobaric (mp) and isochoric (mv) fragilities decrease with increased confinement. They also found that Tg decreased and remains constant with constant volume and pressure confinements. The Tg shifts towards lower temperature as the diameter of the nanoparticles is reduced. Similar to the previously mentioned article, nanoparticle size plays a huge role in synthesis. Another example is that as nanoparticle diameter decreases, the surface area to volume ratio increases meaning smaller nanoparticles affect the Tg making it lower and more stable.
Photoresponsive coumarin-stabilized polymeric nanoparticles
In the article Photoresponsive coumarin-stabilized polymeric nanoparticles as a detectable drug carrier, Priestley et al. demonstrate how to create nanoparticles of hydrophobic homopolymer poly Ɛ-caprolactone with coumarin moieties (CPCL) suspended in water. Due to their application for drug transportation and medical imaging, polymer nanoparticles are very useful and Priestley et al. are experimenting with creating stable nanoparticles suspended in water. Photoresponsive coumarin-stabilized nanoparticles are effective drug carriers as they not only incorporate the drugs into their hydrophobic (water hating) core, but they exhibit intrinsic fluorescence without the use of additional fluorescent probes. This allows for coumarin-stabilized nanoparticles to be efficient detectable drug carriers as they exhibit these fluorescent characteristics and the nanoparticle can be imagined within the cell. Consistent with his other articles, narrow size distribution of nanoparticle provide greater stability. The nanoparticles of CPCL are about 40 nm in diameter therefore possessing greater stability. CPCL nanoparticles have great cellular uptake properties (like incorporating drugs in their core), have narrow size distribution, and, when treated with coumarin, have intrinsic fluorescent properties, making it an excellent drug carrier candidate.