Temperature-dependent self-assembly and rheological behavior of a thermoreversible pmma–PnBA–PMMA triblock copolymer gel

Self-assembly and mechanical properties of triblock copolymers in a mid-block selective solvent are of interest in many applications. Herein, we report physical assembly of an ABA triblock copolymer, [PMMA–PnBA–PMMA] in two different mid-block selective solvents, n-butanol and 2-ethyl-1-hexanol. Gel formation resulting from end-block associations and the corresponding changes in mechanical properties have been investigated over a temperature range of −80 °C to 60 °C, from near the solvent melting points to above the gelation temperature. Shear-rheometry, thermal analysis, and small-angle neutron scattering data reveal formation and transition of structure in these systems from a liquid state to a gel state to a percolated cluster network with decrease in temperature. The aggregated PMMA end-blocks display a glass transition temperature. Our results provide new understanding into the structural changes of a self-assembled triblock copolymer gel over a large length scale and wide temperature range.