Birefringence of Thin Uniaxial Polymer Films Estimated Using the Light Polarization Ellipse

Postolache, Mihai; Dimitriu, Dan Gheorghe; Nechifor, Cristina Delia; Condurache-Bota, Simona; Cloşca, Valentina; Dorohoi, Dana Ortansa

doi:10.3390/polym14051063

Cited by 6 publications

(10 citation statements)

References 55 publications

(92 reference statements)

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“…The anisotropic 2D ordering of the film structure was confirmed from the birefringence observed by using polarizing optical microscopy. The presence of birefringence is usually attributed to the anisotropic nature of a material due to the difference in refraction of light along different directions in its shape and structure. − Therefore, to understand the existence of any asymmetrical ordering, the films were investigated using cross-polarized light at various angles of rotations (0 and 45°). The flat areas [light falling perpendicular to the 2D sheets in the x – y plane] of the films showed no birefringence signifying structural symmetry and in-plane isotropy.…”

Section: Resultsmentioning

confidence: 99%

Imine-Linked 2D Conjugated Porous Organic Polymer Films for Tunable Acid Vapor Sensing

Gayle,

Roy,

Gupta

et al. 2024

ACS Appl. Mater. Interfaces

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Two-dimensional (2D) films of conjugated porous organic polymers (C-POPs) can translate the rich in-plane functionalities of conjugated frameworks into diverse optical and electronic applications while addressing the processability issues of their crystalline analogs for adaptable device architectures. However, the lack of facile single-step synthetic routes to obtain large-area high-quality films of 2D-C-POPs has limited their application possibilities so far. Here, we report the synthesis of four mechanically robust imine-linked 2D-C-POP free-standing films using a single-step fast condensation route that is scalable and tunable. The rigid covalently bonded 2D structures of the C-POP films offer high stability for volatile gas sensing in harsh environments while simultaneously enhancing site accessibility for gas molecules due to mesoporosity by structural design. Structurally, all films were composed of exfoliable layers of 2D polymeric nanosheets (NSs) that displayed anisotropy from disordered stacking, evinced by out-of-plane birefringent properties. The tunable in-plane conjugation, different nitrogen centers, and porous structures allow the films to act as ultraresponsive colorimetric sensors for acid sensing via reversible imine bond protonation. All the films could detect hydrogen chloride (HCl) gas down to 0.05 ppm, far exceeding the Occupational Safety and Health Administration's permissible exposure limit of 5 ppm with fast response time and good recyclability. Computational insights elucidated the effect of conjugation and tertiary nitrogen in the structures on the sensitivity and response time of the films. Furthermore, we exploited the exfoliated large 2D NSs and anisotropic optoelectronic properties of the films to adapt them into micro-optical and triboelectric devices to demonstrate their real-time sensing capabilities.

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Section: Resultsmentioning

confidence: 99%

Imine-Linked 2D Conjugated Porous Organic Polymer Films for Tunable Acid Vapor Sensing

Gayle,

Roy,

Gupta

et al. 2024

ACS Appl. Mater. Interfaces

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“…This method—based on the determination of the rotation angle of the polarization ellipse relative to the principal axes of the AL—is a simple procedure consisting of the rotation of the analyzing polarizer around the light propagation direction until the maximum light intensity is obtained [ 36 ]. In this position, the transmission direction of the analyzer is parallel to the big axis of the polarizing ellipse.…”

Section: Optical Methods For Linear Birefringence Evaluationmentioning

confidence: 99%

“…The irregular reduction in Δ n with the thickness might be due to the inability to produce a good alignment of the macromolecules from the films having a larger thickness. Birefringence of PVA was additionally studied using the polarizing ellipse method [ 36 ]. In this case, the sample processing was made in two stages: firstly, before completion of solvent removal a rubbing action was applied; secondly, after total solidification of the sample mechanical drawing was performed.…”

Section: Optically Birefringent Polymer Materials and Their Applicationsmentioning

confidence: 99%

Review on Optical Methods Used to Characterize the Linear Birefringence of Polymer Materials for Various Applications

et al. 2023

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Optical polymers are recognized for their high transparency, raised flexibility, low cost, and good film-forming ability; hence, they introduce a multitude of benefits in a wide range of devices, such as information storage, displays, optical communications, and filters. Among the optical properties, birefringence is an essential parameter in practical cases that demand the control of the state of polarization of light. This review is focused on describing some fundamental and applicative aspects concerning the optical birefringence of the polymer materials. First, elementary notions depicting the phenomenon of light double refraction in macromolecular media are provided. Furthermore, the most relevant optical techniques to determine birefringence are reviewed by highlighting the working principle and mathematical basis for computing this parameter. Then, a series of investigations of optically birefringent polymers are described, summarizing the most utilized approaches to induce light double refraction in such materials. The selected results are analyzed in relation to the pursued applications. In the end, the future of this scientific domain is briefly presented by establishing the research paths that need further exploration. Moreover, the novel directions that could be formulated and might contribute to certain considerable advancements in the materials employed in the modern optical technologies are mentioned.

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“…Many optical detection methods combining spectral analysis, microfluidic technology, and optical metamaterials with high efficiency, sensitivity, and detection ability have been developed and widely used in food, medicinal, and agricultural industries for biological detection and chemical analysis [11][12][13][14]. The optical properties of biological samples are different from the macroscopic optical constants of solids.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Optical Properties and Activity of Wheat Stripe Rust Urediospores

Chen

Yao

2023

Agriculture

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Stripe rust is one of the most common diseases challenging the safe production of wheat. Rapid identification and analysis of urediospores, responsible for disease transmission, are the key to preventing and controlling stripe rust. The current spore detection is time-consuming and requires auxiliary equipment, but many optical detection methods and sensors with high efficiency, sensitivity, and detection ability have been developed and widely used. Thus, the investigation of optical parameters is the prerequisite for optical sensitive detection and is detailed in this study. Firstly, the microscopic images and surface elements of wheat stripe rust urediospores were obtained using a high-resolution electron microscope and an energy spectrum analyzer. The reflectivity and absorptivity spectra in the near-infrared band of active/inactivate urediospores were measured. Further, the optical parameters, such as reflection phase shift, complex refractive index, and dielectric constant, of the urediospores were analyzed based on electromagnetic theory and Kramers–Kronig relation. The results revealed that the urediospores have a strong tolerance to near-infrared light, and the real part of the complex refractive index n was between 1.0 and 1.4. These observations indicate that whether the spores are active or not has little effect on the real part and dielectric constant of the complex refractive index but has a significant impact on the imaginary part and extinction coefficient of the complex refractive index, and the corresponding relationship between the optical properties of urediospores and biological components was established. These findings were verified with HPLC-MS and Near-Infrared Spectroscopy Analysis Technology and lay a theoretical foundation for detecting urediospores of wheat stripe rust by using optical sensors. The study provides a reference for the analysis of optical characteristics of other biological samples.

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Birefringence of Thin Uniaxial Polymer Films Estimated Using the Light Polarization Ellipse

Cited by 6 publications

References 55 publications

Imine-Linked 2D Conjugated Porous Organic Polymer Films for Tunable Acid Vapor Sensing

Imine-Linked 2D Conjugated Porous Organic Polymer Films for Tunable Acid Vapor Sensing

Review on Optical Methods Used to Characterize the Linear Birefringence of Polymer Materials for Various Applications

Investigation of Optical Properties and Activity of Wheat Stripe Rust Urediospores

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