Date of Award
12-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
School
Polymer Science and Engineering
Committee Chair
Dr. Sarah Morgan
Committee Chair School
Polymer Science and Engineering
Committee Member 2
Dr. Derek Patton
Committee Member 2 School
Polymer Science and Engineering
Committee Member 3
Dr. Sergei Nazarenko
Committee Member 3 School
Polymer Science and Engineering
Committee Member 4
Dr. William Jarrett
Committee Member 4 School
Polymer Science and Engineering
Committee Member 5
Dr. Travis Thornell
Abstract
The focus of this dissertation is the synthesis of block copolymers containing polyisobutylene (PIB) and polystyrene (PS) and the characterization of their mechanical properties at high strain rate under impact. Understanding the influence of various factors like molecular weight, PIB:PS ratio, chain architecture, and morphology on the dynamic response of block copolymers is pivotal for the design of better impact resistant materials in blast and ballistic mitigation.
The first chapter provides an overview of key energy absorbing mechanisms like chain scission and chain pullout along with important polymeric properties like entanglements, ductility, mechanophores and impedance mismatch that can be used to tune the impact resistance and visualize the deformations in polymers at high strain rates. The second chapter focusses on investigating the physical and chemical properties of polymers responsible for chain scission during ultrasonication. Herein, we have established a detailed synthesis method based on controlled radical polymerization to incorporate mechanophores at block junctions in triblock copolymers. We established the importance of conformations on directing chain scission at the interface of our triblock copolymers. In the third chapter, we focus on the sensitivity shown by polymers at high strain rates during split Hopkinson pressure bar SHPB testing. We establish the importance of chain pullout, ductility, number of interfaces, entanglement density, multiaxial stress, and adiabatic heating in governing the dynamic response under compression. The plastic flow under deformation was visualized using digital image correlation. In the third chapter we focused on tuning the morphology of phase separated block copolymers via solvent vapor annealing and homopolymer blending. We found a way to tune the long-range order via the vapor pressure of solvents and selective swelling of PIB and PS domains depending on solubility parameter of the solvents used. We also established that the general trends in ratio of chain length of homopolymer to the corresponding block in the polymer (denoted by a value), wet brush regime, and dry brush regime of diblock/homopolymer blending reported for diblocks do not hold true for triblock/homopolymer blending. Finally, the fourth chapter summarizes the major conclusions of our work and recommends some future work to further advance the design of impact resistant block copolymers suitable for applications in blast and ballistic mitigation.
Copyright
Parth Vagholkar, 2025
Recommended Citation
Vagholkar, Parth, "Synthesis and Design of Energy Dissipating PIB-PS Block Copolymers for Evaluating Their Structure-Property-Performance Relationships Under High Strain Rate Impact" (2025). Dissertations. 2415.
https://aquila.usm.edu/dissertations/2415
Included in
Nanoscience and Nanotechnology Commons, Polymer and Organic Materials Commons, Structural Materials Commons