Category: Spring 2014
Dr. Priestley came to speak to the students at Lafayette College in April 2014. The talk is divided into two parts. He talks about his research on nanoparticles and introduces Janus particles. Take a look!
The Interdisciplinary Seminar Class had the privilege to speak with Dr. Priestly.
Here’s what happened:
1. Jennifer :Can you explain your background and interests growing up? What targeted you on this path [of polymer nanoparticle research]?
2. Michael: Your paper focused more on the process of nanoparticles and developing them. I was wondering if you could speak to the application, such as drug delivery?
3. Barbara: I remember our class talked about the use of coumarin in the photo-responsive coumarin article and one of our professors brought up the use of coumarin as opposed to other organic compounds that can have similar affects in the human body. So I was wondering why coumairn was used?
4. Barbara: So in your lab, have you tried to look at other ones [responsive moieties]?
5. Barbara: So how would that [temperature responsive moieties] react to the human body?
6. Morgan: You were talking about the application of these [nanoparticles] and how you get your inspiration to come up with different research ideas. So, is it ever the case that either in your group or any other groups where you undertake a project idea after communicating with a partner in medicine or industry where they would say this is something we’re struggling with and need help developing? field?
7. Morgan: It’s funny that you say that actually, because I was speaking to a professor about the difference between academia and industry and one of the main things she said was that in academia you’re doing it to understand how the world works, and in industry, you’re trying to solve problems.
8. More on Polystyrene particles, including an interesting find.
9. Morgan: Just based on my extreme frustration with doing experiments on the micron level, I’m wondering how long does the layering take?
10. Michael: Since you’re working on such a small scale, I get that you can kind of physically see what’s going on. But when you’re trying a new reaction and you aren’t sure what happens in new conditions, how do you know that you did it, or didn’t do it?
11. Barbara: I have two questions: 1) are the names listed on your articles the names of your graduate students that work in your lab? and 2)What are the implications of nanoparticles?
12. Barbara: You mention in the FNP (flash nano-precipitation) article, that grand scale applications can get a bit iffy because as you increase polystyrene concentration, the size also increases. So in terms of making it [nanoparticle precipitation] competitive with companies using emulsification, how do you propose that would work?
13. Morgan: What is it exactly about your research or your job that drives you the most? What get’s you up in the morning to do this everyday?
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.