RJ Vogler's REU Experience (Summer 2018)

Week 8 mainly consisted of working in lab, attending some REU meetings, and going to see a baseball game with other REU students. In lab, I continued working with cellulose-polyacrylic acid (PAA) membranes and tried an experiment on polyvinylidene fluoride (PVDF) and PVDF-PAA membranes.  Early in the week, I continued to study how much the cellulose-PAA membrane can reject molecules of different sizes.  One notable conclusion that I made is that the membrane could have some holes that are larger than its ordinary pores that inhibit its rejection of small and moderately-sized molecules.  This conclusion stems from the fact that the membrane only rejected 83% of a molecule that was at least 200x larger than the two molecules that I tested before it, which were both poorly rejected by the membrane.  After finishing my testing of the rejection of a cellulose-PAA membrane, I tried to capture calcium ions with a similar membrane.  The beginning of this process invol...

Week 7 consisted continuing my work in lab, attending a presentation about the GRE test, and spending some time with my fellow REU students. In lab this week, I got to begin the study of the cellulose-polyacrylic acid (PAA) membrane that I made last week.  One parameter of this membrane that I got to look at was permeability, which is an indicator of how fast substances flow through the membrane.  One interesting thing about this parameter for membranes containing PAA is that it should change as the pH of the inlet solution and membrane change.  This is because the units of PAA's repeating structure become negatively charged (rather than neutral) at higher pH values, and thus, repel each other and cause swelling of PAA that constricts the pores.  To test for this behavior in the cellulose-PAA membrane, I soaked the membrane in an acidic solution in an effort to reduce the swelling of PAA and measured the flow of a similar solution through the membrane afterwards; I...

This week consisted of working in lab, meeting with my research group, spending time with my fellow REU students, and heading home for a bit on the weekend. In lab, I got to see some cool machines in action and make a membrane out of cellulose and polyacrylic acid (PAA). One of the machines that I got to see was a scanning electron microscope (SEM). This SEM also had an energy-dispersive x-ray spectrometer (EDS), which is capable of analyzing the elements present in an SEM image of a membrane sample. During my two visits, I got to see this machine be used to study the amount of iron in a polyvinylidene fluoride-PAA membrane that I loaded with iron last week. One type of EDS analysis that was done on this membrane is mapping, which marks the locations of different elements in an SEM image. Some of the maps of a portion of my membrane that all correspond to the same SEM image are directly below. The carbon and fluorine are both part of PVDF, Iron Carbon Fluorine wh...

Week 5 of the program involved working in the lab, giving a presentation, listening to others’ presentations, taking a tour of Alltech’s headquarters, and visiting the latino festival in downtown Lexington. In lab, I got to continue my study of the increase or decrease in outlet flow rate of a membrane as I changed inlet pH. The membrane that I used was the one that I helped make out of polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA) earlier in the summer. While it may seem counterintuitive to decrease the outlet flow rate of a membrane, it could come in handy in certain scenarios. For exampl e, if th is type of membrane were modified to react with certain substances that flow through it, the ability to slow down the flow through the membrane would provide it with more time to breakdown these substances. One new experiment that I got to experience in lab this week was the measurement of the surface charge of a membrane. To take this measurement, I had to prepare a small...