Paper Number
PO114
Session
Poster Session
Title
Tuning ordering transitions in BCP hydrogels via shear and magnetic fields
Presentation Date and Time
October 12, 2022 (Wednesday) 6:30
Track / Room
Poster Session / Riverwalk A
Authors
- Kresge, Grace (University of Minnesota, Chemical Engineering and Materials Science)
- Mikal, Chelsea (University of Minnesota, Chemical Engineering and Materials Science)
- Calabrese, Michelle A. (University of Minnesota, Chemical Engineering and Materials Science)
Author and Affiliation Lines
Grace Kresge, Chelsea Mikal and Michelle A. Calabrese
Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55414
Speaker / Presenter
Kresge, Grace
Keywords
directed systems; gels; polymer solutions
Text of Abstract
A central issue in block copolymer (BCP) processing is creating materials with long-range order with precisely tunable properties. Maintaining this high degree of ordering throughout moderate to high strains imposed upon materials in roll-to-roll and extrusion processing poses additional challenges. This work addresses these challenges by examining the effects of both shear and magnetic fields on inducing novel disorder-to-order transitions in BCP micelle solutions. The system consists of moderately concentrated (20%) aqueous solutions of poloxamers (symmetric PEO-PPO-PEO triblocks) which undergo a magnetic field-induced and a shear-mediated transition from disordered spherical micelles to crystalline packed phases of spherical or elongated micelles. Using a magneto-rheological device, the effect of strain amplitude, frequency, magnetic field intensity, and magnetization time on the maximum gel modulus, phase, and relaxation kinetics were systematically studied. Design parameters for poloxamer hydrogels with tunable moduli relevant to applications in drug delivery and flexible electronics were established. Moreover, recovery experiments display the promising robustness of these systems to large, sudden changes in shear forces that are present in processing, as modulus returns to same value up to 100% strain. These experiments also further illuminate the kinetics and thermodynamics of this anomalous magnetically-induced sol-gel transition. Overall, this work provides new insights into processing BCPs via a combination of external fields to yield better control over material properties.