Title: Impact of Helical Chain Shape in Sequence-Defined Polymers on Polypeptoid Block Copolymer Self-Assembly

Abstract

Controlling the self-assembly of block copolymers with variable chain shape and stiffness is important for driving the self-assembly of functional materials containing nonideal chains as well as for developing materials with new mesostructures and unique thermodynamic interactions. The polymer helix is a particularly important functional motif. In the helical chain, the traditional scaling relationships between local chain stiffness and space-filling properties are not applicable; this in turn impacts the scaling relationships critical for governing self-assembly. Polypeptoids, a class of sequence-defined peptidomimetic polymers with controlled helical secondary structure, were used to systematically investigate the impact of helical chain shape on block copolymer self-assembly in a series of poly(n-butyl acrylate)-b-polypeptoid block copolymers. Small-angle X-ray scattering (SAXS) of the bulk materials shows that block copolymers form hexagonally packed cylinder domains. By leveraging sequence control, the polypeptoid block was controlled to form a helix only at the part either adjacent to or distant from the block junction. Differences in domain size from SAXS reveal that chain stretching of the helix near the block junction is disfavored, while helical segments at the center of cylindrical domains contribute to unfavorable packing interactions, increasing domain size. Finally, temperature-dependent SAXS shows that helix-containing diblock copolymers disorder at lowermore » temperatures than the equivalent unstructured diblock copolymers; we attribute this to the smaller effective N of the helical structure resulting in a larger entropic gain upon disordering. These results emphasize how current descriptions of rod/coil interactions and conformational asymmetry for coil polymers do not adequately address the behavior of chain secondary structures, where the scalings of space-filling and stiff-elastic properties relative to chain stiffness deviate from those of typical coil, semiflexible, and rodlike polymers.« less

Authors:

Davidson, Emily C. ^[1]; Rosales, Adrianne M.  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-0207-7661"
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Patterson, Anastasia L.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-3875-1195"
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Russ, Boris ^[2]; Yu, Beihang ^[1]; Zuckermann, Ronald N.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-3055-8860"
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Segalman, Rachel A.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-4292-5103"
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+ Show Author Affiliations

1. Univ. of California, Santa Barbara, CA (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Foundry

Publication Date:

2018-03-02

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1530345

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Macromolecules

Additional Journal Information:

Journal Volume: 51; Journal Issue: 5; Journal ID: ISSN 0024-9297

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY