Fully hydrated hybrid membranes based on a polyelectrolyte mixed with an ionic liquid possess gas permeation properties of significant interest for CO2 capture applications.

Block copolymers have been extensively studied due to their ability to spontaneously self-organize into a wide variety of morphologies that are valuable in energy-, medical-, and conservation-related (nano)technologies. While the phase behavior of bicomponent diblock and triblock copolymers is conventionally governed by temperature and individual block masses, it is demonstrated here that their phase behavior can alternatively be controlled through the use of blocks with random monomer sequencing. Block random copolymers (BRCs), i.e., diblock copolymers wherein one or both blocks are a random copolymer comprised of A and B repeat units, have been synthesized, and their phase behavior, expressed in terms of the order-disorder transition (ODT), has been investigated. The results establish that, depending on the block composition contrast and molecular weight, BRCs can microphase-separate. We also report that large variation in incompatibility can be generated at relatively constant molecular weight and temperature with these new soft materials. This sequence-controlled synthetic strategy is extended to thermoplastic elastomeric triblock copolymers differing in chemistry and possessing a random-copolymer midblock.

Strong physical gels derived from thermoplastic elastomeric ABA triblock copolymers solvated with a midblock-selective oil continue to find use in increasingly diverse applications requiring highly elastic and mechanically robust soft materials with tunable properties. In this study, we first investigate the morphological characteristics of thermoplastic elastomer gels (TPEGs) derived from a homologous series of linear A­(BA) n multiblock copolymers composed of styrene and hydrogenated isoprene repeat units and possessing comparable molecular weight but varying in the number of B-blocks: 1 (triblock), 2 (pentablock), and 3 (heptablock). Small-angle X-ray scattering performed at ambient temperature confirms that (i) increasing hydrogenation reduces the microdomain periodicity of the neat copolymers and (ii) increasing the oil concentration of the TPEGs tends to swell the nanostructure (increasing the periodicity), but concurrently decreases the size of the styrenic micelles, to different extents depending on the molecular architecture. Complementary dissipative particle dynamics simulations reveal the level to which midblock bridging, which is primarily responsible for the elasticity in this class of materials, is influenced by both oil concentration and molecular architecture. Since constrained topological complexity increases with increasing block number, we introduce a midblock conformation index that facilitates systematic classification of the different topologies involved in nearest-micelle bridge formation. Those possessing at least one bridged and one looped midblock with no dangling ends are found to be the most predominant topologies in the pentablock and heptablock networks.

Conventional insect repellent treatments for fibers, fabrics, and garments suffer from limited durability to repeated laundering and, depending on the insecticide, potential irritation, or toxicity. In this work, electrospinning was employed to control the composition of hierarchically structured functional microscale to nanoscale fibers for tunable insect repellent release by physically incorporating picaridin into nylon-6,6 nanofibers. The size and morphology of nylon fibers were unaffected by picaridin incorporation, even at loading concentrations up to 50 wt%. Picaridin release kinetics were largely dependent on loading concentration and temperature, as picaridin-nylon intermolecular interactions were minimal affording diffusion based release. Coaxial nanofibers, in which the sheath component has potential to protect additives in the core for more durable fabrics and act as a diffusion barrier for extended release applications, were also developed and demonstrated altered release kinetics compared to monofilament analogues, indicating the capability to further tune release behavior.

As energy needs continue to drive the development of biogas and fossil‐fuel technologies, methods by which to selectively remove basic (NH3) and acidic (CO2) gases are becoming increasingly important, especially in light of global climate change. Block copolymers are considered as suitable membrane candidates in gas separations due to the ability of such copolymers to microphase‐separate and spontaneously form nanoscale morphologies that exhibit spatially modulated chemical specificity. Incorporation of charged moieties along the midblock of a thermoplastic elastomeric multiblock copolymer yields an amphiphilic block ionomer possessing a flexible molecular network stabilized by rigid endblocks. The presence of hydrophilic microdomains introduces an important consideration regulating molecular transport: humidity. In this study, solvent‐templating paradigms are employed to control the morphologies of midblock‐sulfonated pentablock ionomers, as discerned by electron microscopy and X‐ray scattering. The effect of humidity on the permeation of NH3, CO2, and N2 is then investigated through the resulting membranes. As expected, NH3 permeates significantly faster than N2, especially under humid conditions. Although not as pronounced, similar behavior is observed for CO2, thereby establishing that this block ionomer is generally selective to humidified polar gases.

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Unsaturated polydienes are frequently hydrogenated to yield polyolefins that are more chemically stable. Here, the effects of partial hydrogenation on the phase behavior and nanostructure of polyisoprene-containing block copolymers are investigated. To ensure access to the order-disorder transition temperature (T) over a wide temperature range, we examine copolymers with at least one random block. Dynamic rheological and scattering measurements indicate that T increases linearly with increasing hydrogenation. Small-angle scattering reveals that the temperature-dependence of the Flory-Huggins parameter changes and the microdomain period increases, while the interfacial thickness decreases. The influence of hydrogenation becomes less pronounced in more constrained multiblock copolymers.

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