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Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers

Krishnasamy, Velmurugan; Qu, Wentao; Chen, Changlong; Huo, Haohui; Ramanagul, Karthick; Gothandapani, Velraj; Mehl, Georg H.; Zhang, Qilu; Liu, Feng

Authors

Velmurugan Krishnasamy

Wentao Qu

Changlong Chen

Haohui Huo

Karthick Ramanagul

Velraj Gothandapani

Qilu Zhang

Feng Liu



Abstract

Block copolymers (BCPs), comprising a poly(methyl methacrylate) (PMMA) block and a poly(cholesteryloxyhexyl methacrylate) (PChMA) block, were synthesized via reversible addition–fragmentation chain transfer polymerization. The self-assembly of the liquid crystalline BCPs was characterized by differential scanning calorimetry, polarized optical microscopy, and synchrotron-based small/wide-angle X-ray scattering. The results indicate the formation of both tilted and nontilted chiral smectic (SmC* and SmA*) phases. A phase transition from the SmA* to SmC* phase on cooling was observed for BCPs but not for PChMA homopolymers. The layer spacing (5.00 ± 0.18 nm) between those can be controlled to maintain the number of ChMA units while varying the lengths of the PMMA block, thus introducing systematically the SmC* phase. Furthermore, BCPs with the short PMMA block showed inversion of chirality at specific temperatures; however, for PChMA attached with the long PMMA block, no chirality inversion was observed. This mode of chirality switching, investigated by circular dichroism, NMR, and theoretical studies, is associated with the methyl substituents in the backbone affecting the packing of the polymers. The basic rules, described here, have the potential to be implemented for the design of a wide range of functional materials, where helix–helix conversion is of use.

Citation

Krishnasamy, V., Qu, W., Chen, C., Huo, H., Ramanagul, K., Gothandapani, V., …Liu, F. (2020). Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers. Macromolecules, 53(11), 4193-4203. https://doi.org/10.1021/acs.macromol.9b02264

Journal Article Type Article
Acceptance Date May 4, 2020
Online Publication Date May 21, 2020
Publication Date Jun 9, 2020
Deposit Date May 27, 2020
Publicly Available Date May 22, 2021
Journal Macromolecules
Print ISSN 0024-9297
Electronic ISSN 1520-5835
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 53
Issue 11
Pages 4193-4203
DOI https://doi.org/10.1021/acs.macromol.9b02264
Keywords Block copolymer; Cholesterol; Liquid crystals; Self-assembly; Chirality inversion
Public URL https://hull-repository.worktribe.com/output/3511634
Publisher URL https://pubs.acs.org/doi/10.1021/acs.macromol.9b02264

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©2020 The authors. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder







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