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Block copolymers with tunable compositions offer theability todirectly control the interaction strength between the two blocks andtherefore polymer properties. The miscibility of an A–B blockcopolymer can be increased by introducing B or B-like comonomers intothe A block, and literature has shown that both the amount and thedistribution of these comonomers affect the compatibility of the twoblocks. Sequence-defined block copolymers in which one can exactlycontrol the composition and comonomer distribution provide a uniqueopportunity to control the overall strength of segregation. Here,sequence-defined block copolymers have been synthesized via azide–alkynecoupling using polystyrene and sequence-specific polypeptoids (N-substitutedglycines) with 2-methoxyethyl side chains. These polystyrene-polypeptoidblock copolymers readily self-assemble into hexagonally packed andlamellar morphologies. N-(2-phenylethyl)glycine residues,which have a styrene-like side chain, were introduced throughout thepolypeptoid block to increase the compatibility with the polystyreneblock. As the compatibility increased, the strength of segregationand therefore the block copolymer order–disorder transitionsdecreased. The polystyrene–polypeptoid block copolymers providea tunable platform for further studies on the effect of compositionand sequence design on self-assembly and block copolymer properties. [ABSTRACT FROM AUTHOR]

Polymerized ionic-liquids (PILs) are promising materialswhoseionic properties can be tuned based on their chemistry. By incorporatingPILs into block copolymer (BCP) structures, it is possible to providecomplementary functionality (i.e., structural stability) and transporttunability to ion-conducting materials. In this study, we describethe self-assembly and conductivity of novel poly(styrene-block-histamine methacrylamide) diblock copolymers (PS-b-PHMA) and the resulting PS-b-PIL derivatives obtainedafter treatment with trifluoroacetic acid (TFA). These materials self-assembleinto ordered BCP structures with tunable domain sizes as demonstratedby small-angle X-ray scattering (SAXS) and transmission electron microscopy(TEM). PS-b-PHMA membranes show conductivities upto 2 × 10–4S/cm at room temperature, whichincrease byan order of magnitude in the presence of acid. In addition, both PHMA-and PIL-based membranes exhibit lower water uptake (λ = 4–6and 8–10, respectively) in comparison with most proton conductingmembranes reported elsewhere. The low water content in these membranestranslates into a stronger effect of morphology on transport behavior,resulting in a measurable increase in ion conductivity as a functionof conducting channel size. [ABSTRACT FROM AUTHOR]

Conjugated rod-coil diblock copolymers self-assemble due to a balance of liquid crystalline (rod-rod) and enthalpic (rod-coil) interactions. Previous work has shown that while classical block copolymers self-assemble into a wide variety of nanostructures, when rod-rod interactions dominate self-assembly in rod-coil block copolymers, lamellar structures are preferred. Here, it is demonstrated that other, potentially more useful, nanostructures can be formed when these two interactions are more closely balanced. In particular, hexagonally packed polylactide (PLA) cylinders embedded in a semiconducting poly(3-alkylthiophene) (P3AT) matrix can be formed. This microstructure has been long-sought as it provides an opportunity to incorporate additional functionalities into a majority phase nanostructured conjugated polymer, for example in organic photovoltaic applications. Previous efforts to generate this phase in polythiophene-based block copolymers have failed due to the high driving force for P3AT crystallization. Here, we demonstrate that careful design of the P3AT moiety allows for a balance between crystallization and microphase separation due to chemical dissimilarity between copolymer blocks. In addition to hexagonally packed cylinders, P3AT-PLA block copolymers form nanostructures with long-range order at all block copolymer compositions. Importantly, the conjugated moiety of the P3AT-PLA block copolymers retains the crystalline packing structure and characteristic high time-of-flight charge transport of the homopolymer polythiophene (μh∼ 10-4 cm2 V-1 s-1) in the confined geometry of the block copolymer domains. [ABSTRACT FROM AUTHOR]