The self-assembly behavior of linear ABA triblock copolymers has been utilized for developing a variety of functional materials such as thermoplastic elastomers, solid electrolytes, separation membranes, and artificial muscles. Due to the distinctive molecular architecture of ABA triblock copolymers, the polymers will undergo specific self-assembly processes into various nanostructures when a solution of ABA triblock copolymers is introduced to a B-block selective solvent. Although much of the focus in ABA triblock copolymer self-assembly has been on equilibrium nanostructures, little attention has been paid to the guiding principles of nanostructure formation during non-equilibrium processing conditions. Here, a quantitative method for controlling ABA triblock copolymer hierarchical structures using solvent-non-solvent rapid injection processing will be presented. Plasmonic nanocomposite hydrogels containing gold nanoparticles and hierarchically-ordered hydrogels exhibiting photonic band gap properties were assembled within minutes using this rapid-injection technique. The resulting self-assembled structures (micelles, microgels, and hydrogels) for a single ABA triblock copolymer after injection into water was dependent on the initial concentration of the polymer, with respect to the overlap concentration (<i>c</i>*), in the initial co-solvent/polymer mixture. The concentration dependence of the final nanostructures after injection into water was universal for all ABA triblock copolymers in this study (with varying molecular characteristics like molecular weight, hydrophobic block chemical composition, and hydrophobic block volume fraction) while maintaining the hydrophobic-hydrophilic-hydrophobic polymer block sequence. In the dilute regime we produce micelles. Near <i>c</i>* and in the semi-dilute regime, we see microgels. In the concentrated regime, the polymer forms a hydrogel. The underlying theme of the presentation will highlight how polymer chain architecture and non-equilibrium processes can be utilized to create nanostructured materials.

Solvent-induced self-assembly of triblock copolymers to create nanostructured hydrogels exhibiting plasmonic and photonic band gap properties

2019 Fall National Meeting

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