TY - JOUR
T1 - Impact of Helical Chain Shape in Sequence-Defined Polymers on Polypeptoid Block Copolymer Self-Assembly
AU - Davidson, Emily C.
AU - Rosales, Adrianne M.
AU - Patterson, Anastasia L.
AU - Russ, Boris
AU - Yu, Beihang
AU - Zuckermann, Ronald N.
AU - Segalman, Rachel A.
N1 - Funding Information:
We gratefully support from the NSF-DMR Polymers Program through Grant 1608297. A.M.R. and A.L.P. also gratefully acknowledge the National Science Foundation for graduate fellowships. This work acknowledges user facilities at both the Advanced Light Source and the Stanford Synchrotron Radiation Lightsource, supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515. The research reported here made use of shared facilities of the UCSB MRSEC (NSF DMF 1720256), a member of the Materials Research Facilities Network. This work also made use of facilities at the Molecular Foundry, a Lawrence Berkeley National Laboratory user facility supported by the Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DEAC02-05CH11231. In addition, we thank Scott Danielsen for helpful discussions.
Funding Information:
We gratefully support from the NSF-DMR Polymers Program through Grant 1608297. A.M.R. and A.L.P. also gratefully acknowledge the National Science Foundation for graduate fellowships. This work acknowledges user facilities at both the Advanced Light Source and the Stanford Synchrotron Radiation Lightsource, supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contracts DE-AC02-05CH11231 and DE-AC02-76SF00515. The research reported here made use of shared facilities of the UCSB MRSEC (NSF DMF 1720256), a member of the Materials Research Facilities Network. This work also made use of facilities at the Molecular Foundry, a Lawrence Berkeley National Laboratory user facility supported by the Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DE- AC02-05CH11231. In addition, we thank Scott Danielsen for helpful discussions.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/3/13
Y1 - 2018/3/13
N2 - 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 lower 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.
AB - 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 lower 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.
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U2 - 10.1021/acs.macromol.8b00055
DO - 10.1021/acs.macromol.8b00055
M3 - Article
AN - SCOPUS:85043758591
SN - 0024-9297
VL - 51
SP - 2089
EP - 2098
JO - Macromolecules
JF - Macromolecules
IS - 5
ER -