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Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations

Levine, William G. and Seo, Youngmi and Brown, Jonathan R. and Hall, Lisa M. (2016) Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations. Journal of Chemical Physics, 145 (23). Art. No. 234907. ISSN 0021-9606. doi:10.1063/1.4972141.

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Tapered diblock copolymers are similar to typical AB diblock copolymers but have an added transition region between the two blocks which changes gradually in composition from pure A to pure B. This tapered region can be varied from 0% (true diblock) to 100% (gradient copolymer) of the polymer length, and this allows some control over the microphase separated domain spacing and other material properties. We perform molecular dynamics simulations of linearly tapered block copolymers with tapers of various lengths, initialized from fluids density functional theory predictions. To investigate the effect of sequence dispersity, we compare systems composed of identical polymers, whose taper has a fixed sequence that most closely approximates a linear gradient, with sequentially disperse polymers, whose sequences are created statistically to yield the appropriate ensemble average linear gradient. Especially at high segregation strength, we find clear differences in polymer conformations and microstructures between these systems. Importantly, the statistical polymers are able to find more favorable conformations given their sequence, for instance, a statistical polymer with a larger fraction of A than the median will tend towards the A lamellae. The conformations of the statistically different polymers can thus be less stretched, and these systems have higher overall density. Consequently, the lamellae formed by statistical polymers have smaller domain spacing with sharper interfaces.

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Additional Information:© 2016 AIP Publishing. Received 18 September 2016; accepted 1 December 2016; published online 20 December 2016. We thank Thomas H. Epps III for useful discussions. This work was initially supported in part by the H.C. “Slip” Slider Professorship in Chemical and Biomolecular Engineering and by an allocation in computing time from the Ohio Supercomputer Center. This material is also based upon the work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award No. DE-SC0014209 (during the writing of this work L.M.H. and J.R.B. were supported by this award). Additionally, during the writing of this work, Y.S. was supported by the National Science Foundation under Grant No. 1454343.
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Department of Energy (DOE)DE-SC0014209
Issue or Number:23
Record Number:CaltechAUTHORS:20161221-095203161
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Official Citation:Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations William G. Levine, Youngmi Seo, Jonathan R. Brown, Lisa M. Hall, William G. Lowrie The Journal of Chemical Physics 2016 145:23
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73058
Deposited By: Tony Diaz
Deposited On:21 Dec 2016 17:58
Last Modified:11 Nov 2021 05:10

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