Title: Structural and Optical Response of Polymer-Stabilized Blue Phase Liquid Crystal Films to Volatile Organic Compounds

Abstract

Engineering useful mechanical properties into stimuli-responsive soft materials without compromising their responsiveness is, in many cases, an unresolved challenge. For example, polymer networks formed within blue-phase liquid crystals (BPs) have been shown to form mechanically robust films, but the impact of polymer networks on the response of these soft materials to chemical stimuli has not been explored. In this work, we report on the response of polymer-stabilized BPs (PSBPs) to volatile organic compounds (VOCs, using toluene as a model compound) and compare the response to BPs without polymer stabilization and to polymerized nematic and cholesteric phases. We find that PSBPs generate an optical response to toluene vapor (change in reflection intensity under crossed polars) that is sixfold greater in sensitivity than the polymerized nematic or cholesteric phases and with a limit of detection (140 ± 10 ppm at 25 °C) that is relevant to the measurement of permissible exposure limits for humans. Additionally, when compared to BPs that have not been polymerized, PSBPs respond to a broader range of toluene vapor concentrations (5000 vs <1000 ppm) over a wider temperature interval (25–45 vs 45–53 °C). We place these experimental observations into the context of a simple thermodynamic model to exploremore » how the PSBP response reflects the effect of toluene on competing contributions of double-twisted LC cylinders, disclinations, and polymer network to the free energy that controls the PSBP lattice spacing. Overall, we conclude that the mechanical and thermal stability of PSBPs, when combined with their optical responsiveness to toluene, make this class of self-supporting LCs a promising one as the basis of passive and compact (e.g., wearable) sensors for VOCs.« less

Authors:

Yang, Yu ^[1]; Kim, Young-Ki  ^[2];

• Search DOE PAGES for author "Kim, Young-Ki"
• Search DOE PAGES for ORCID "0000-0002-4420-3489"

Wang, Xin ^[3]; Tsuei, Michael ^[3]; Abbott, Nicholas L.  ^[3]

• Search DOE PAGES for author "Abbott, Nicholas L."
• Search DOE PAGES for ORCID "0000-0002-9653-0326"

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+ Show Author Affiliations

1. Cornell Univ., Ithaca, NY (United States); Univ. of Wisconsin, Madison, WI (United States)
2. Cornell Univ., Ithaca, NY (United States); Pohang Univ. of Science and Technology (POSTECH) (Korea, Republic of)
3. Cornell Univ., Ithaca, NY (United States)

Publication Date:

Fri Aug 14 00:00:00 EDT 2020

Research Org.:

Cornell Univ., Ithaca, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); US Army Research Office (ARO); National Science Foundation (NSF)

OSTI Identifier:

1803889

Grant/Contract Number:  

SC0019762; W911NF-15-1-0568; W911NF-19-1-0071; CBET-1803409; CBET-1852379; DMR-1719875

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 12; Journal Issue: 37; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; science & technology; materials science; liquid crystal; blue phase; polymer network; volatile organic compound; optical and structural response; sensor