The development of nanostructured polymeric systems containing directionally continuous poly(ionic liquid) (poly(IL)) domains has considerable implications toward a range of transport-dependent, energy-based technology applications. The controlled, synthetic integration of poly(IL)s into block copolymer (BCP) architectures provides a promising means to this end, based on their inherent ability to self-assemble into a range of defined, periodic morphologies. In this work, we report the melt-state phase behavior of an imidazolium-containing alkyl−ionic BCP system, derived from the sequential ring-opening metathesis polymerization (ROMP) of imidazolium-and alkyl-substituted norbornene monomer derivatives. A series of 16 BCP samples were synthesized, varying both the relative volume fraction of the poly(norbornene dodecyl ester) block (f DOD = 0.42−0.96) and the overall molecular weights of the block copolymers (M n values from 5000−20 100 g mol −1 ). Through a combination of small-angle X-ray scattering (SAXS) and dynamic rheology, we were able to delineate clear compositional phase boundaries for each of the classic BCP phases, including lamellae (Lam), hexagonally packed cylinders (Hex), and spheres on a body-centered-cubic lattice (S BCC ). Additionally, a liquid-like packing (LLP) of spheres was found for samples located in the extreme asymmetric region of the phase diagram, and a persistent coexistence of Lam and Hex domains was found in lieu of the bicontinuous cubic gyroid phase for samples located at the intersection of Hex and Lam regions. Thermal disordering was opposed even in very low molecular weight samples, detected only when the composition was highly asymmetric (f DOD = 0.96). Annealing experiments on samples exhibiting Lam and Hex coexistence revealed the presence of extremely slow transition kinetics, ultimately selective for one or the other but not the more complex gyroid phase. In fact, no evidence of the bicontinuous network was detected over a 2 month annealing period. The ramifications of these results for transport-dependent applications targeting the use of highly segregated poly(IL)-containing BCP systems are carefully considered.

Thermoplastic elastomer hydrogel networks, based on swelling of nanostructured blends of amphiphilic, sphere-forming AB diblock and ABA triblock copolymers, provide direct access to thermally processable plastics that exhibit exceptional elastic recovery and fatigue resistance even after hydration. In such two-component systems, the ratio of ABA triblock copolymer to AB diblock copolymer is used to control the resultant swelling ratio, system modulus, and overall mechanical response. In this report, we introduce a simplified one-component alternative which exploits a single-component, photoreactive AB diblock copolymer precursor to controllably generate ABA triblock copolymer in situ during melt-processing. This was accomplished using efficient photoinduced [4 + 4] cycloaddition (λ = 365 nm) between terminal anthracene units on a ω-anthracenylpolystyrene-b-poly(ethylene oxide) diblock copolymer precursor (SO-anth, f PS = 0.13, M n = 70 100 g mol −1 ) to produce the desired amount of polystyrene-bpoly(ethylene oxide)-b-polystyrene (SOS) triblock copolymer. The amount of SOS triblock copolymer formed was tunable (from 11.7 to 45 mol %) using UV exposure time (2 to 20 min, ∼30 mW cm −2 ), giving direct control over swelling and mechanical properties in the resultant hydrogels produced upon subsequent vitrification of the melt sample followed by addition of water. Hydrogels produced in this manner were found to exhibit dynamic shear moduli and shape preservation characteristics typical of preblended, two-component SO/SOS TPE hydrogels of similar SOS concentrations.