Mechanics of Triblock Copolymer & Dual Triblock Copolymer Gels

The goal of this project is to compare the mechanical behavior of triblock copolymer and dual triblock copolymer gels with the slip-tube network (STN) theory. These gels are used in a variety of different applications ranging from model surgery and ballistics gels to bike seat cushions. The triblock copolymer gels we study are composed of styrenic ABA triblock copolymers, such as SEBS, and aliphatic mineral oil. Dual triblock copolymer gels are similar, but contain two unique styrenic ABA triblock copolymers. The copolymers in gels form a physically-crosslinked network which explains their mechanical robustness. To characterize the mechanical behavior of these gels, we perform quasi-static tensile tests. The results of which are nonlinear, elastic stress-extension curves. We fit this data using the slip-tube network model that yields the crosslinked network and chain entanglement modulus contributions. These modulus contributions allow us to understand and quantitatively interpret trends in stress-extension curves as functions of our formulation parameters (copolymer concentration, block fractions, and molecular weight). Comparison of experimental modulus contributions with their theoretical expectation further provides an updated understanding of gels' microstructure.