Matteaus Klonowski

Understanding the Swelling Mechanism of Stimuli Responsive Organically-Modified Silica

April 3, 2021   /  

Name: Mattaeus Klonowski
Majors: Chemistry, Physics
Advisors: Dr. Paul Edmiston, Dr. Cody Leary

Stimuli-responsive polymers (SRPs) are materials which exhibit a change in physical properties upon a change in local environment. Some SRPs can expand in volume upon absorption of liquid, and are referred to as swellable materials. The two swellable materials studied in this project were sodium polyacrylate (SPA) and swellable organically-modified silica (SOMS). SPA swells only upon absorption of water, whereas SOMS can swell upon the absorption of a variety of organic solvents. Both SPA and SOMS generate a pressure when swollen within a confined volume. Although SPA generates greater swelling pressure than SOMS, SOMS takes significantly less time to reach maximum swelling pressure. SOMS exhibits immediate pressure generation upon contact with solvent, whereas SPA has an initially slow buildup in pressure generation. The different behaviors of SPA and SOMS are due to the different solvent-network interactions driving the swelling of each material. SOMS was swollen with different solvents, and maximum swelling pressure was found to have minimal dependence on absorbed solvent. However, the time it took for SOMS to reach maximum swelling pressure varied significantly with absorbed solvent, and may correlate to the viscosity of the solvent. Modeling SOMS as an exponential spring revealed a difference in the elasticity of SOMS for different amounts of absorbed solvent. Swelling mechanisms governing the pressure generation of SOMS remain unknown. However, progress was made by fitting relevant models to the swelling of SOMS. The next step in determining the swelling mechanism of SOMSwill be correlating physical processes to the models used.

Click here to view Matteaus’ presentation. (NOTE: A Wooster login is required to view this presentation)

Matteaus will be online to field comments on April 16:
8-10am EDT (Asia: evening, Africa/Europe: afternoon)

30 thoughts on “Understanding the Swelling Mechanism of Stimuli Responsive Organically-Modified Silica”

  1. Nice work Matt! If you had time to take more data, what do you think would you explore next?

    1. Thank you Dr. Leary! I would look into the relationship between the solvent used to induce the swelling of SOMS and effective spring constant and thermodynamic values for swelling. It would be interesting to see if there is any dependence on solvent for either of the models I used. Fitting swelling curves to the Voigt model may also help elucidate the physical process driving the swelling of SOMS.

  2. Really cool project Matt! Do you think if SOMS is modified with polymer or metals that your results will be the same?

    1. Thank you for the question Heather! I think incorporating polymers or metals into SOMS might change the shape of the swelling curves. Depending on the characteristics of the polymers/metals, the swelling pressure generated by SOMS, and which solvents can be used to initiate swelling, would likely vary.

  3. Nice work Matt! How did your experiences in IS shape your interest moving forward? Do you enjoy the combined theoretical and experimental focus, or do you favor one side of the research?

    1. Thank you for the question Dr. Sobeck! I have always been interested in materials science, and I think this project was an opportunity to gain another reinforcing perspective on that. Since I didn’t take a class dedicated to polymer science, it was an interesting challenge to teach myself about this topic. I definitely enjoyed digging into the different theories used to describe the swelling of typical stimuli-responsive polymers and how they may or may not relate to the swelling of SOMS.

  4. Some really interesting results here! When you measured swelling pressure vs. time using different solvents to trigger the swelling, did you use exactly the same mass of SOMS in each experiment? That variable will impact swell rate and maximum pressure.

    1. Great question Dr. Bonvallet! I used masses of SOMS that were 250 (+/- 2.5) mg for each measurement. Assuming that a 1% variation in mass has a negligible contribution to maximum swelling pressure, the results are indicative of a real relationship between max swell pressure and solvent used. Additionally, I measured max swell pressure in triplicate for each solvent used to ensure replicability of the results.

      1. Thanks for the response. The two things that you can measure directly — maximum pressure, and rate of swell — may be mutually intertwined or could be completely separate. I don’t see a general trend that connects the two; ethanol is slow with a weaker swell, but toluene is almost as slow with the strongest swell. Is that your thinking as well, that swelling pressure and swelling rate are orthogonal properties?

        1. Great follow-up question Dr. Bonvallet! Based on my initial results it seems that maximum pressure and swell rate are not related, as the former does not significantly vary with solvent but the latter does. However, to be sure, more data would need to be collected and analysis done to determine the orthogonality of these properties. Flory-Rehner theory and the Voigt model have been used previously to describe the swelling of typical swellable materials, and a deeper analysis of SOMS through this lens may grant more insight regarding this topic.

  5. This is a very nice work!!
    As you said, SOMS takes far less time to react the maximum swelling force.
    Does the speed and magnitude of its swelling vary depending on the identity of organic solvents being absorbed?

    1. Great question Aileen! Based on my results, the magnitude of swelling pressure generated by SOMS, upon absorption of solvent, does not depend much on the solvent used (only up to about 10% variation), but the time it takes to reach maximum swelling pressure does depend significantly on the solvent used.

  6. Very interesting project, Matt. I have two questions. What did you find of greatest value in your IS experience? Any speculation on the theoretical basis for the difference between the swelling curve of ethanol on the one hand and hexane, acetone, and acetonitrile on the other?

    1. Thank you! Getting guidance from my advisors to plan out experiments, and then using the data I collected to compare to different theories, in order to interpret my results, has given me confidence in continuing to do research in a real-world setting after I graduate. The difference between the swelling curves of ethanol and the other solvents used to induce swelling is likely due to the stronger intermolecular forces present for ethanol compared to the other solvents, specifically hydrogen bonding. This also results in ethanol having a greater viscosity.

  7. Strong science Matt! Going off your hypothesis that viscosity of the solvent could dictate the time it takes SOMS to reach maximum swelling pressure, do you have any future experiments in mind that would confirm this…potentially for the next wave of IS students?? Were you more passionate about the modeling or benchwork aspect of the project? I imagine it is quite difficult formulating a multidisciplinary IS so really nice job!!

    1. Thank you and great question Chris! One experiment that could be done to give more insight into the effects of solvent on the time it takes SOMS to reach maximum swelling pressure is to measure the enthalpy and entropy changes of swelling with different solvents. Additionally, the Voigt model could be used, which is often used with typical stimuli-responsive polymers, to describe the dependence of solvent on swelling kinetics. I definitely enjoyed the modeling aspect of my IS project more.

    2. John Nugent ’20 worked out a system for varying the viscosity of toluene solutions by dissolving prescribed amounts of polystyrene. The two materials have matched dielectric constants (i.e. same “polarity”) but their relative proportions could create anything from a free-flowing fluid to a gooey syrup.

      1. That could be a great follow-up IS project, I would be excited to see the results!

  8. Nice job Matt! How does the maximum swelling pressure of SOMS and SPA compare to those of similar stimuli-responsive polymers?

    1. Great question Holly! Sodium polyacrylate (SPA) is a well-known swellable material, most of which are only capable of swelling upon the absorption of water. SOMS on the other hand cannot absorb water, but will swell upon absorption of organic solvents, a unique property among swellable materials. SOMS has a lesser maximum swelling pressure compared to SPA and most other swellable materials, but with respect to the amount of absorbed liquid, SOMS has a relatively greater max swell pressure.

  9. Hi Matt! Really cool project and great presentation! Could you explain in more detail why you think the time it takes to reach maximum swelling pressure relates to the viscosity of the solvent? The figure is hard for me to read.

    1. Thank you Anna! Essentially, the time it takes for the swelling pressure to reach a maximum takes longer for certain solvents, such as ethanol (shown in the figure). For the five solvents I tested in triplicate, I found that there may be a correlation between this maximum swell time and the viscosity of the solvent used to induce swelling (shown in the table).

  10. Fantastic job, Matt! It was great to get to see and understand your project more fully today.

Comments are closed.