Please consider attending the following:
MATERIALS ENGINEERING
“Synthesis and Characterization of Model Acrylic-based Polymer Gels.”
By
Travis L. Thornell
Purdue MSE Ph.D. Final Exam
Advisor: Professor Kendra A. Erk
ABSTRACT
Materials made from polymer gel networks are important to many everyday applications in health care to building materials. These gel materials can be easily synthesized in various ways, but characterizing the
overall material mechanics and properties are challenging due to the soft nature of their respective bulk structures. Model acrylic-based copolymer gels were investigated to understand the fundamental characteristics and mechanical properties from different
crosslinking and gelation processes.
First, model hydrogels with fracture-healing characteristics similar to materials needed for injectable drug delivery systems were studied using shear rheology to determine timescales of fully healed networks.
The industrially available gel was a thermoreversible triblock copolymer composed of poly(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) in 2-ethyl hexanol to form a physical gel from polymer-solvent interactions. A methodology of quantifying
healing was developed from an applied constant shear rate and monitoring the shear stress response of the samples. The maximum shear stress responses observed during fracture and re-fracture after allowing the sample to rest indicated gel healing. Given sufficient
time, gel healing was determined to be dependent on testing temperature and polymer concentration. The time for fully healed networks was achieved on the order of minutes for the lowest concentration of 5 vol. % at temperatures of 28 and 25°C to several hours
for the highest concentration of 6 vol. % at lower temperatures of 23 and 20°C.
Lastly, spherical superabsorbent polymer (SAP) gels with silica nanoparticles (SiO2) were synthesized from inverse suspension polymerization to form chemically crosslinked composite hydrogels of polyacrylamide
and poly(acrylic acid). The hydrogels were studied for understanding the interaction of SiO2 nanoparticles within polyelectrolyte networks for use as a chemical admixture for internal curing of high performance concrete. The composite SAP hydrogels
were produced with bare or silane-functionalized SiO2 particles to investigate the effects on swelling performance, shape, and cement paste microstructure.
Date: Tuesday, April 17, 2018
Time: 9:30 A.M.
Place: ARMS 1028