Spin Coated Contact Angle Was Contacted!

Aryana p -

CONTACT ANGLE CON’T

One of the immediate questions following last week’s experiment was whether the values of contact angle for spin coated QAMS onto another PDMS membrane would be different than a pure QAMS membrane. In other words, would having a layer beneath the QAMS polymer change the surface properties, or surface energy, of the QAMS membrane?

Drumroll please…yes it would! This week I was able to test the spin coated membranes of all weight percentages. The process is exactly the same as the experiment done last week, except the membranes were exchanges for membranes that had spin coated QAMS on top of PDMS. From repeating the same process outlined last week, I was able to obtain Wu and OWRK values, which are two different models for surface energy(which is useful to analyze the intermolecular bonds between the surface and drop of liquid).

Upon analysis of all the data, I was able to determine that overall, for both Wu and OWRK decreased for spin coated membranes, meaning the attractions between the drops of diiodomethane (nonpolar liquid) and water to the surface of the membrane were weaker.

CAPTURING THE CARBON

As another set of experiments this week, I was able to put the membranes into the system that I described in my first blog. In other words, I was able to test the membranes against the CO2 and NO2 compressed gas mixture. The process is fairly simple. Everyday, I place a membrane into the membrane chamber. I check the flowmeters to ensure they are set at the correct pressure, and then I run script. The script is a set of instructions for the system over 24 hours. Around every four hours the system is told to increase the concentration of carbon dioxide into the system from 100 ppm, 400 ppm, 1000 ppm, 14000 ppm. The computer is able to track the humidity, retentate, and permeate concentration using the IRGAs mentioned in blog 1.

So far, I was able to measure the 5% QAMS and 10% QAMS spin coated membranes. After analyzing the data, it was clear that an increase from 5 to 10 percent did increase the amount of CO2 that was able to be filtered which is very promising for this project.

 

More Posts

Comments:

All viewpoints are welcome but profane, threatening, disrespectful, or harassing comments will not be tolerated and are subject to moderation up to, and including, full deletion.

    jahnvi_s
    Hi Aryana! This is so interesting! Do you plan to test spin coated membranes with higher QAMS percentages?
    March 19, 2025 at 3:09 pm - Reply
    lydia_felice
    Sounds like it has been a productive week at the lab! I am excited to hear about how raising the QAMS percentages impacts the amount of CO2 that is filtered. I would also like to hear more about how the contact angle experiments relate to the goal of the project as a whole. The results of these experiments are so interesting, and it will be exciting to see how everything comes together!
    March 21, 2025 at 8:25 am - Reply
    aryana_p
    Hi Jahnvi! That's an interesting question. The interesting thing about the PQAMS solution before I spin coat it on the membrane is that it is mixed with a different polymer called PDMS. Adding PDMS is necessary in order to 1) be able to very the amount of PQAMS in each membrane while keeping the volume of the membrane the same so that I can test the optimal amount of PQAMS in a membrane and 2) be able to create a flexible membrane because a membrane purely made out of PQAMS would not be flexible or strong due to the properties of the polymer backbone of PQAMS. Your question brings up an interesting topic that I did not mention in my initial blogs. PQAMS can only be dissolved in acetone and PDMS can only be dissolved in chloroform. In the solution I mix all together. You can imagine PQAMS and acetone partnered together, and PDMS partnered together. I forcibly mix these two pair into solution, and put it under heat to force them to crosslink. Cross linking is forcing the polymer chains to join, which can only happen under heat. If I were to add more of PQAMS the cross linking would not happen fast enough causing phase separation. Phase separation is when the two polymers essentially do not mix and separate in solution while their solvents evaporate off. In a physical sense, the membrane would contain a lot of bubbles and unevenness, because you essentially be seeing two different polymers instead of one linked polymer chain.
    April 2, 2025 at 10:46 am - Reply
    aryana_p
    Hi Dr. Felice! I talked about this in next week's blog but I can run it down quickly here. The special thing about the polymer PQAMS is that it has amine groups that create moisture swing sites. Moisture swing sites allow the membrane to use a humidity gradient to drive air through the membrane rather than a a pressure or energy extensive flow across the membrane of air. Essentially the membrane can soak up carbon dioxide and water in a humid environment, and release carbon dioxide in a dry environment. The water contact angle tests allows us to see whether the PQAMS membranes that I created actually have the affinity with water that is desired for these moisture swing sites.
    April 2, 2025 at 10:50 am - Reply

Leave a Reply

Your email address will not be published. Required fields are marked *