(6hm) Understanding the Remarkable Physical Chemistry of Novel Polymer Materials: How Does Intricate Chemical Functionality Enhance Material Properties?

Future research directions

Advances in polymer synthesis techniques have enabled the creation of soft materials with features once thought to be impossible: precise structures and dynamic responses across multiple length scales, mechanical robustness that does not inhibit processability, and well-defined transport properties that can be tuned via external stimuli. These next-generation polymers show great promise to solve current and future societal needs affecting the environment, energy, health, and food accessibility. Making these novel materials useful, however, requires deep understanding of their fundamental physics.

My lab will investigate how the enhanced functionality of technologically important polymer materials alters their thermodynamics, dynamics, and structure-property relationships. To study these complex systems, we will routinely – but not exclusively – use cryogenic and analytical electron microscopy, scattering (soft and hard X-rays, neutrons, light, and electrons), rheology (linear and non-linear), and theoretical modeling. Initially, we will focus on three project areas:

1) Polymerization induced encapsulation

2) Vitrimer gels - elucidation of nanostructure and dynamics

3) Interfacial dielectric properties of polymer nanocomposite capacitors

Graduate research

“Characterization of hydroxypropyl methylcellulose acetate succinate solid dispersions in the solid-state and during dissolution”

Department of Chemical Engineering and Materials Science, University of Minnesota-Twin Cities Advisors: Timothy P. Lodge and Marc A. Hillmyer

During my PhD thesis, I developed novel strategies for characterizing the structure-property relationships of solid dispersions, which are blends of a pharmaceutical drug and a polymer. First, I pioneered the use transmission electron microscopy techniques to map the spatial distribution of the drug and polymer in the bulk [1-2]. Second, I discovered – using novel X-ray scattering and electron microscopy assays – that the drug and polymer form metastable nanostructures during dissolution in aqueous solvent [3]. My work conclusively showed that nanoscale phenomena directly affect the efficacy of solid dispersions, and the characterization strategies I designed will guide the rational design of future solid dispersion formulations [4].

Postdoctoral research

“Understanding the fundamental structure and dynamics of next-generation vitrimer materials” Matière Molle et Chimie, ESPCI Paris

Advisors: Ludwik Leibler and Michel Cloître

For my postdoctoral work, I investigated the fundamental physics of vitrimers, a novel class of polymers that are crosslinked like thermosets, but flow when heated like thermoplastics. While vitrimers are robust and versatile, poor understanding of their microstructure hinders their transfer from the laboratory to commercialization. Using a suite of experimental tools and theoretical modeling, I discovered that polyethylene vitrimers exhibit unique self-assembly behavior, which has significant repercussions on processing and material properties [5]. Currently, I am developing experimental and theoretical tools to understand the linear viscoelastic properties of model vitrimer materials.

Teaching Interests:

Teaching experience

As an undergraduate at UT Austin, I served as a tutor/grader for several courses, including Material and Energy Balances, Transport Phenomena, and Unit Operations. As a graduate student at the University of Minnesota, I was a TA for courses in Reaction Engineering/Kinetics and Plant Design. I also served as a course instructor for Mass Transfer and Separations. In this role, I taught semi-weekly recitation sessions for a class of 20 students.

In addition to formal courses, I also devoted significant time to scientific outreach. During my Ph.D. I founded Science For All, a nonprofit program dedicated to teaching science to the urban Twin Cities community. For this program, I designed scientific lessons and experiments for K-12 students, managed relationships with partner schools, and raised funding for supplies and transportation. Since its founding in 2014, SFA has grown to include 30 mentors and works with almost 100 K-12 students. Furthermore, from 2012-2014 I served as the head coordinator for Polymer Day, a day-long outreach event focused on teaching high school students about polymer science. I organized the event schedule, recruited mentors, and designed experiments that highlighted concepts from polymer chemistry and physics. In 2016 I co-authored a journal article describing the program and its success at teaching high school students about polymer science [6].

Future teaching goals

Because of my varied teaching experiences during my academic career, I can teach all core undergraduate chemical engineering courses. I am also interested to teach elective/graduate courses in areas related to soft materials, such as polymer chemistry and physics, colloidal science, transmission electron microscopy, scattering techniques, rheology, nanoscience, etc.

Furthermore, I plan to promote diversity in chemical engineering by starting a mentorship program for underrepresented minorities in the sciences. The program will include two branches. One branch will focus on in-class lessons and experiments for K-12 students (similar to Science For All). The other branch will aim at placing high school students in academic and industrial internships. This program will not only strengthen the relationship between the public and scientific communities, but also provide opportunities for graduate students and postdocs to act as mentors.

Selected successful proposals:

European Synchrotron Radiation Facility: ID02 Beamline (2018)

Main proposer

Awarded 72 hrs of ultra small-angle X-ray scattering time to study vitrimer nanostructure

Advanced Photon Source at Argonne National Laboratory: DND-CAT Beamline (2018)

Main proposer

Awarded 72 hrs of simultaneous small- and wide-angle X-ray scattering time to study vitrimer nanostructures

SOLEIL Synchrotron: SWING Beamline (2018)

Main proposer

Awarded 72 hrs of small-angle X-ray scattering time to study vitrimer nanostructures

Campus France PRESTIGE Co-financing Grant Award (2017)

Sole proposer

Awarded 41000 € to conduct research on the fundamental physics of vitrimer materials

National Science Foundation Graduate Research Fellowship Program Award (2011)

Sole proposer

Awarded $100,000 to conduct graduate research in chemical engineering

Selected publications:

1) Ricarte, R.G.; Lodge, T.P.; Hillmyer, M.A. "Detection of pharmaceutical drug crystallites in solid dispersions by transmission electron microscopy." Molecular Pharmaceutics 2015, 12, 983–990.

2) Ricarte, R.G.; Lodge, T.P.; Hillmyer, M.A. "Elucidation of the spatial distribution of small molecules in amorphous polymer matrices by electron energy-loss spectroscopy." Langmuir 2016, 32, 7411­–7419.

3) Ricarte, R.G.; Li, Z.; Johnson, L.M.; Ting, J.M.; Reineke, T.M.; Bates, F.S.; Hillmyer, M.A.; Lodge, T.P. “Direct Observation of Nanostructures During Aqueous Dissolution of Polymer/Drug Particles.” Macromolecules, 2017, 50, 3143–3152.

4) Ricarte, R.G.; Li, Z.; Johnson, L.M.; Van Zee, N.; Porter, Schmitt; R.; W.W.; Hillmyer, M.A.; Lodge, T.P. “Recent advances in understanding the nanoscale phenomena of solid dispersions.” In preparation.

5) Ricarte, R.G.; Tournilhac, F.; Leibler, L. “Semi-crystalline polyethylene vitrimers: macro- and micro-phase separation create hierarchical structure.” In preparation.

6) Ting, J.M.; Ricarte, R.G.;* Schneiderman, D.K.;* Saba, S.A.; Jiang, Y.; Hillmyer, M.A.; Bates, F.S.; Reineke, T.M.; Macosko, C.M.; Lodge, T.P. “Polymer Day: Outreach Experiments for High School Students.” Journal of Chemical Education, 2017, 94, 1629–1638. (*Equal authorship)