scholarly journals Multifunctional sensors based on liquid crystals scaffolded in nematic polymer networks

RSC Advances ◽  
2021 ◽  
Vol 11 (61) ◽  
pp. 38694-38702
Author(s):  
Xiyun Zhan ◽  
Dan Luo ◽  
Kun-Lin Yang
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Temperature Change ◽  
Color Change ◽  
Polymer Network ◽  
Polymer Networks ◽  
Eye Color ◽  
Naked Eye ◽  
Nematic Polymer

Naked-eye color change as a result of temperature change or VOC exposure was demonstrated in a nematic polymer network-stabilized liquid crystal (PNLC) system.

scholarly journals Effect of Amorphous Crosslinker on Phase Behavior and Electro-Optic Response of Polymer-Stabilized Blue Phase Liquid Crystals

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 48
Author(s):  
Kyung Min Lee ◽  
Urice Tohgha ◽  
Timothy J. Bunning ◽  
Michael E. McConney ◽  
Nicholas P. Godman
Keyword(s):  
Liquid Crystals ◽  
Phase Behavior ◽  
Color Change ◽  
Response Times ◽  
Polymer Network ◽  
Polymer Networks ◽  
Pentaerythritol Triacrylate ◽  
Phase Liquid ◽  
Blue Phase ◽  
Polymer Stabilized

Blue phase liquid crystals (BPLCs) composed of double-twisted cholesteric helices are promising materials for use in next-generation displays, optical components, and photonics applications. However, BPLCs are only observed in a narrow temperature range of 0.5–3 °C and must be stabilized with a polymer network. Here, we report on controlling the phase behavior of BPLCs by varying the concentration of an amorphous crosslinker (pentaerythritol triacrylate (PETA)). LC mixtures without amorphous crosslinker display narrow phase transition temperatures from isotropic to the blue phase-II (BP-II), blue phase-I (BP-I), and cholesteric phases, but the addition of PETA stabilizes the BP-I phase. A PETA content above 3 wt% prevents the formation of the simple cubic BP-II phase and induces a direct transition from the isotropic to the BP-I phase. PETA widens the temperature window of BP-I from ~6.8 °C for BPLC without PETA to ~15 °C for BPLC with 4 wt% PETA. The BPLCs with 3 and 4 wt% PETA are stabilized using polymer networks via in situ photopolymerization. Polymer-stabilized BPLC with 3 wt% PETA showed switching between reflective to transparent states with response times of 400–500 μs when an AC field was applied, whereas the application of a DC field induced a large color change from green to red.

A new phenothiazine-based fluorescent probe for detection of hydrazine with naked-eye color change properties

2021 ◽  
Author(s):  
Nian Rao ◽  
Yi Le ◽  
Dan Li ◽  
Yan Zhang ◽  
Qin Wang ◽  
...  
Keyword(s):  
Fluorescent Probe ◽  
Color Change ◽  
Eye Color ◽  
Naked Eye

scholarly journals Reverse switching of surface roughness in a self-organized polydomain liquid crystal coating

2015 ◽  
Vol 112 (13) ◽  
pp. 3880-3885 ◽  
Author(s):  
Danqing Liu ◽  
Ling Liu ◽  
Patrick R. Onck ◽  
Dirk J. Broer
Keyword(s):  
Surface Roughness ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Light Exposure ◽  
Polymer Network ◽  
Polymer Networks ◽  
Domain Size ◽  
Interference Microscopy ◽  
Light Illumination ◽  
Modulation Amplitude

In this work we propose randomly ordered polydomain nematic liquid crystal polymer networks to reversibly generate notable jagged relief patterns at a polymer coating surface by light illumination. The domain size is controlled by the addition of traces of partly insoluble fluorinated acrylate. The photoresponse of the coating is induced by a small amount of copolymerized azobenzene monomers. Upon exposure to UV light, azobenzene undergoes trans to cis isomerization, resulting in a change in molecular order and packing within each domain. The extent of this effect and its directionality depends on the domain orientation. Localized to domain level, this morphological change forms large 3D spikes at the surface with a modulation amplitude of more than 20% of the initial thickness. The process is reversible; the surface topographical patterns erase within 10 s by stopping the light exposure. A finite element model is applied to simulate the surface topography changes of the polydomain coating. The simulations describe the formation of the topographic features in terms of light absorption and isomerization process as a function of the director orientation. The random director distribution leads to surface structures which were found to be in close agreement with the ones measured by interference microscopy. The effect of domain size on surface roughness and depth modulation was explored and related to the internal mechanical constraints. The use of nematic liquid crystal polydomains confined in a polymer network largely simplifies the fabrication of smart coatings with a prominent triggered topographic response.

scholarly journals Detection of organic amines using a ratiometric chromophoric fluorescent probe with a significant emission shift

2020 ◽  
Vol 44 (7-8) ◽  
pp. 475-481
Author(s):  
Dan Wu ◽  
Yi Liu ◽  
Fei Zheng ◽  
Shi-Qi Rong ◽  
Tao Yang ◽  
...  
Keyword(s):  
Fluorescent Probe ◽  
Nucleophilic Addition ◽  
High Selectivity ◽  
Color Change ◽  
Intramolecular Charge Transfer ◽  
Signaling Mechanism ◽  
Eye Color ◽  
Naked Eye ◽  
Spectrometric Measurements ◽  
Organic Amines

Taking advantages of both the well-known α,β-unsaturated structure and the special nucleophilicity of organic amines toward its acceptor moieties, intramolecular charge transfer as a signaling mechanism is used to design and synthesize a new ratiometric chromophoric fluorescent probe (BI-CA-ID) with large emission shifts toward organic amines. This probe is employed for the detection of organic amines with high selectivity and sensitivity and a “naked-eye” color change (from red to colorless). Ultraviolet–visible and fluorescence spectrometric measurements are used to determine detection limits as low as 0.024 and 0.43 μM. Furthermore, nucleophilic addition of the amine on the α,β-unsaturated of BI-CA-ID indicated that the sensing mechanism occurs via interruption of the π-conjugation.

scholarly journals A new rhodamine fluorescent OFF-ON-OFF probe for selective sensing of Fe3+ and AcO- in aqueous media and living cells

2018 ◽  
Vol 238 ◽  
pp. 04002
Author(s):  
Qinglei Liu ◽  
Huimin Liu ◽  
Yanan Lei ◽  
Yan Gao ◽  
Bing Zhao
Keyword(s):  
Fluorescence Probe ◽  
Color Change ◽  
Aqueous Media ◽  
Living Cells ◽  
Eye Color ◽  
Naked Eye ◽  
Fluorescent Response ◽  
Good Biocompatibility ◽  
Anions And Cations ◽  
Displacement Approach

A new fluorescent chemosensor for Fe3+ was developed based on a rhodamine platform. L displayed highly selective and sensitive “OFF-ON” fluorescence response and naked-eye color change to Fe3+ in aqueous solution. The resulting L-Fe3+ complex was found to act as a selective“ ON-OFF” fluorescence probe for AcO- against common anions and cations with a Fe3+ displacement approach. The detection limits of L to Fe3+ and L-Fe3+ complex to AcO- were estimated to be 6.04×10-8 mol/L and 7.51×10-8 mol/L, respectively. The good biocompatibility of L enabled the investigation of fluorescent response for Fe3+ and AcO- in living Ana-1 cells by confocal microscope.

Photoresponsive Azobenzene Liquid Crystal Polymer Networks: In Situ Photogenerated Stress Measurement

2010 ◽  
Author(s):  
Yanira Torres ◽  
Timothy White ◽  
Amber McClung ◽  
William Oates
Keyword(s):  
Liquid Crystal ◽  
Stress Measurement ◽  
Polymer Network ◽  
Polymer Networks ◽  
Liquid Crystal Polymer ◽  
Polymerization Process ◽  
Polarization Angle ◽  
Structure Property ◽  
Crystal Polymer ◽  
Azobenzene Mesogens

Azobenzene liquid crystal polymers and polymer networks are adaptive materials capable of converting light into mechanical work. Often, the photomechanical output of the azobenzene liquid crystal network (azo-LCN) is observed as a bending cantilever. The response of these materials can be either static (e.g. a simple bending cantilever) or dynamic (e.g. oscillating cantilever of 20–270 Hz). The resulting photomechanical output is dependent upon the domain orientation of the polymer network and the wavelength and polarization of the actinic light. Polydomain azobenzene liquid crystal polymer networks, which have the capability of bending both backwards and forwards with the change of polarization angle, are of particular interest. In the current study, three azo-LCNs are compared — two of them are equivalent in all respects except for one contains pendant azobenzene mesogens (1azo, azo-monoacrylate) and the other contains crosslinked azobenzene mesogens (2azo, azo-diacrylate). The third specimen has a combination of both mesogens. The mechanical behavior at different temperatures and examination of structure-property relationships in the polymerization process, including curing temperatures and liquid crystal cell alignment rubbing methods, were explored. Using dynamic mechanical analysis (DMA) the mechanical properties and the photogenerated stress and strain in the polymer are examined. It is found the differences in chemistry do correlate to small variation in the speed of photodirected bending, elastic modulus, and glass transition temperature. Despite these differences, all three azo-LCNs display nearly equivalent photogenerated stresses.

A Novel Polymer Patterning Method based on Pattern Forming States of Liquid Crystals as Templates

2001 ◽  
Vol 709 ◽  
Author(s):  
Shin-Woong Kang ◽  
Samuel Sprunt ◽  
Liang-Chy Chien
Keyword(s):  
Liquid Crystals ◽  
Electric Field ◽  
Polymer Network ◽  
Orientational Order ◽  
Polymer Networks ◽  
Optical Cell ◽  
Uv Illumination ◽  
Patterning Technique ◽  
Pattern Forming ◽  
Third Dimension

ABSTRACTWe describe a new polymer patterning technique that produces controllable morphological and optical anisotropy in a polymer network. This technique is based on the use of pattern-forming states of nematic and cholesteric liquid crystals as templates for forming ordered polymer networks. One and two-dimensional optical patterns are induced by applying an electric field across a narrow gap of an electro-optical cell. These field-induced optical patterns are then stabilized by UV-induced polymerization of a typically 5 wt% reactive monomer in liquid crystal host. Depending on specific conditions (e.g., thickness to pitch ratio of a cholesteric, applied electric field, and wavelength of UV illumination), the polymer captures various degrees of the orientational order and spatial periodicity of the pattern-forming states of liquid crystals. The fidelity of the templating effect is explored using polarizing optical microscopy and SEM. We also describe the effect of UV wavelength on the network morphology and the morphological control over the”third” dimension (normal to the cell substrates).

Rhodamine–benzothiazole conjugate as an efficient multimodal sensor for Hg2+ ions and its application to imaging in living cells

2018 ◽  
Vol 42 (14) ◽  
pp. 11665-11672 ◽  
Author(s):  
Perumal Sakthivel ◽  
Karuppannan Sekar ◽  
Gandhi Sivaraman ◽  
Subramanian Singaravadivel
Keyword(s):  
Rhodamine B ◽  
Color Change ◽  
Living Cells ◽  
Fluorescence Response ◽  
Eye Color ◽  
Naked Eye ◽  
Turn On ◽  
Rhodamine B Dye

A rhodamine B dye bearing a benzothiazole conjugate is designed and synthesized, it shows a highly selective and sensitive naked-eye color change and turn-on fluorescence response to Hg2+ ions.

Liquid Crystal Influenced Self-assembly in Mesogenic Polymer and Liquid Crystal Blends

2004 ◽  
Vol 856 ◽  
Author(s):  
Lanfang Li ◽  
Carmen Otilia Catanescu ◽  
Liang-Chy Chien
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Self Assembly ◽  
Polymer Network ◽  
Monomer Concentration ◽  
Curing Temperature ◽  
Low Molecular Weight ◽  
Photo Polymerization ◽  
Anisotropic Elastic ◽  
Polymerization Conditions

ABSTRACTIn this work, we found that by performing photo-polymerization of the mesogenic monomer RM257 in liquid crystals, well organized polymer walls were formed through out the cell by self-assembly of the polymer within the anisotropic host – the liquid crystal. The polymerization conditions, which were parameterized as UV intensity, photo-reactivity (characterized by photo initiator concentration), curing temperature, monomer concentration and mesophase of the liquid crystal host, were systematically varied. Different liquid crystal host also raised some difference in polymer network. We believe this kind of morphology comes from spinodal decomposition and the anisotropic elastic property of the liquid crystal host. It is found that for RM257 and low molecular weight nematic liquid crystals a monomer concentration of 5% is sufficient to use liquid crystal hosts to work as templates for well structured polymer walls.

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