3 years ago

# Manipulating the ABCs of self-assembly via low-{chi} block polymer design [Chemistry]

Mark W. Matsen, Carol M. Garland, Christopher M. Bates, Robert H. Grubbs, Russell K. W. Spencer, Simon C. Jones, Alice B. Chang, Byeongdu Lee

Block polymer self-assembly typically translates molecular chain connectivity into mesoscale structure by exploiting incompatible blocks with large interaction parameters (χij). In this article, we demonstrate that the converse approach, encoding low-χ interactions in ABC bottlebrush triblock terpolymers (χAC ≲ 0), promotes organization into a unique mixed-domain lamellar morphology, which we designate LAMP. Transmission electron microscopy indicates that LAMP exhibits ACBC domain connectivity, in contrast to conventional three-domain lamellae (LAM3) with ABCB periods. Complementary small-angle X-ray scattering experiments reveal a strongly decreasing domain spacing with increasing total molar mass. Self-consistent field theory reinforces these observations and predicts that LAMP is thermodynamically stable below a critical χAC, above which LAM3 emerges. Both experiments and theory expose close analogies to ABA′ triblock copolymer phase behavior, collectively suggesting that low-χ interactions between chemically similar or distinct blocks intimately influence self-assembly. These conclusions provide fresh opportunities for block polymer design with potential consequences spanning all self-assembling soft materials.

Publisher URL: http://www.pnas.org/content/114/25/6462.short

DOI: 10.1073/pnas.1701386114

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