Analysis of electro-optical properties of surfactant doped polymer dispersed liquid crystal

Analysis of electro-optical properties of surfactant doped polymer dispersed liquid crystal | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Analysis of electro-optical properties of surfactant doped polymer dispersed liquid crystal Wenya Gai, Ran An, Yue Han, Jiabo Zhang, Hui Zhang, Guili Zheng, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6121841/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 12 You are reading this latest preprint version Abstract The narrow working temperature range is one of the significant factors limiting the wide applications of polymer dispersed liquid crystal (PDLC). In this paper, we have prepared a surfactant (Span-80) doped PDLC. The different concentration of Span-80 has a significant impact on the electro-optical properties of PDLC at different temperatures. Based on the experimental results that doping of Span-80 can reduce the driving voltage and shorten the recovery time of PDLC at low temperatures, a ball lubrication model has been proposed. The results from the ideal model are consistent with the experimental results. polymer dispersed liquid crystal low temperature surfactant electro-optical properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1 Introduction Liquid crystal/polymer composites have been a subject of great interest and exploration in recent years. This composite material consists of two parts: polymer and liquid crystal. Polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC) and polymer stabilized liquid crystal (PSLC) are the three primary categories of liquid crystal/polymer composites based on the different concentration of polymer monomer [1–4]. Polymer concentration is more than 30% results in the formation of polymer dispersed liquid crystals. That is, the liquid crystals are randomly dispersed in the polymer matrix in the form of microdroplets. When no electric field is applied, due to the refractive index mismatch between the liquid crystal and the polymer matrix, the PDLC film presents scattering state, i.e., the opaque state. After applying an electric field, the refractive indices of the liquid crystal and polymer match, and the PDLC film presents transparent state. Since PDLC can modulate light without polarizers and orientation layers, it not only reduces the cost but also simplifies the design, making it widely applicable, such as smart windows, sensors, displays, and so on [5–14]. Current researches mainly focus on reducing the driving voltage, shortening the response time. Nanoparticles doped PDLC is a good direction to solve the problem. The nanoparticles added to PDLC are mainly divided into three categories: oxide nanoparticles (e.g., SiO2, BaTiO3, ITO, etc.), quantum dot nanoparticles (e.g., CdS QD, CdSeS/ZnS QD, ZnCdSeS/ZnS QD, etc.) and metal nanoparticles (e.g., Ag, Zn, Au, etc.). Nanoscale doping of graphene, carbon nanotubes, dyes, cellulose, etc. is also common [15–16]. The above work is carried out to improve the electro-optical properties of PDLC at room temperature. However, in applications such as smart windows of automobiles and exterior walls of buildings, PDLC films might experience harsh temperature conditions. When PDLC films are in low temperature conditions, the driving voltage increases and the switching speed between scattering state and transparent state becomes slow. The study of the improvement of their performance at low temperatures becomes particularly important. Xu Jianjun et al. performed a series of studies on PDLC with wide working temperature range. Firstly, researchers have explored ways to improve the performance of PDLC films at high and low temperatures by using liquid crystals with a wide temperature range, monomers and cross-linking agents [17]. The results show that the PDLC films prepared with hexyl acrylate as monomer and 1, 4-butanediol diacrylate as cross-linking agent have excellent electro-optical properties and can work in a wide temperature range. Secondly, polymer dispersed liquid crystal films with good electro-optical properties and wide working temperature range were prepared by optimizing the curing temperature [18]. It was found that when the polymerization temperature is at the clearing point of polymer/liquid crystal mixture, the films have better electro-optical properties and higher contrast ratio (CR) at high temperatures, and faster rise time and decay time at low temperatures. Thirdly, the incorporation of fluorinated liquid crystal into the liquid crystal, which can successfully reduce the driving voltage of the PDLC films at sub-zero temperature, but the contrast ratio at high temperatures is reduced [19]. In all three studies, cross-linking agents and liquid crystals with a wide temperature range were used. The use of cross-linking agents allows the linear molecules to interconnect to form a mesh structure, which improves the strength and elasticity of the polymer material. The wide temperature range of liquid crystals allows PDLC to have a wide working temperature range. PDLC made from prepolymers is not easy to work over a wide temperature range. However, it can be seen from the above discussion that doping can improve the electro-optical properties of PDLC at low temperatures, which requires that the doped substances remain stable at low temperatures. In production and life, products used in low temperature are added surfactants to achieve the purpose of anti-freezing [20–23], then the use of surfactants for doping of PDLC is a new method. This article introduces the surfactant Span-80 into PDLC and studies its effect on the electro-optical properties of PDLC at different temperatures. The temperature range suitable for the working of Span-80 is selected by experiments, and the experimental rules are explained by using the ideal model of ball lubrication. 2 Experiments 2.1 Materials The liquid crystal used in this experiment was a positive nematic liquid crystals PDLC-005 ( n e =1.745, n o =1.52, Δ n =0.225, T Cr-N ﹤-30℃, T N-I =109℃), from Luquan Liquid Crystal Factory. Monofunctional reactive monomers Isononyl Acrylate (INAA), Isobornyl Acrylate (IBOA), Isobornyl Methacrylate (IBOMA), and photo-initiator 1-Hydroxy-Cyclohexylphenyl-Ketone (PI 184) were provided by Changxing Chemical Materials Co., LTD. Prepolymer CN131 was purchased from Sadoma Chemical Co., LTD. Spacer with a diameter of 10μm was provided by Suzhou Nanno Technology Co., LTD. Surfactant Span-80 in this paper was purchased from Xingtai Lanxing Auxiliary Factory. The formulation compositions of the undoped PDLC were given in Table 1. Table 1 The formulation compositions of the undoped PDLC (weight percent) Polymer Polymer: Liquid Crystal INAA IBOA IBOMA CN131 PI 184 17 24 24 32 3 40:60 2.2 Sample Preparation In this experiment, PDLC was prepared by polymerization induced phase separation (PIPS). To study the influence of Span-80 in the PDLC, the mass ratio of polymer to liquid crystal was kept constant (Polymer: Liquid Crystal=40:60) and the concentration of Span-80 was varied (≤2 wt.%). Samples were prepared by doping Span-80 in different concentrations into PDLC (0.5 wt.%, 1.0 wt.%, 1.5 wt.%, 2.0 wt.%). For the comparison of the results, an undoped PDLC sample was also prepared. Firstly, the polymer and the liquid crystal were properly mixed in a vial, which was stirred for 15 minutes to obtain a homogeneous solution. The surfactant Span-80 was added to the homogeneous solution and then continued stirring for 15 minutes. Then the conductive glass coated with indium tin oxide (ITO) on the inner surface was cleaned with anhydrous ethanol, and a small number of spacers were uniformly sprinkled onto the glass surface. Afterwards, 4μl of uniform solution was dropped onto the glass with a pipette gun, and slowly covered with another piece of glass staggered 1cm apart to make a liquid crystal cell with a square area of about 2 cm × 2 cm. Finally, the preparation was exposed under UV light (intensity of 12mW/cm 2 ) for 3 minutes at room temperature, as shown in Fig. 1(a). When no electric field was applied, the disordered liquid crystal droplets were dispersed in the polymer matrix and the film exhibited the scattering state shown in Fig. 1(b). When the electric field was applied, the liquid crystal droplets were ordered along the direction of the electric field, and the film presented the transparent state, as shown in Fig. 1(c). 2.3 Characterizations A sample was placed under the orthogonal polarizer (OLYMPUS BX51) to obtain the POM image. The electro-optical properties of the prepared samples were carried out by constructing an optical circuit, in which a He-Ne laser ( λ = 632.8 nm) was used as the incident light source. The light was passed through the attenuator and the sample in turn, and finally received by the photodetector. The oscilloscope generated a square wave signal with a frequency of 1kHz, which was amplified by an amplifier and was applied to the sample. The electro-optical properties at low temperatures were cooled by a temperature control device. The temperatures for the experimental steps were 8℃, 4℃, 0℃, -4℃, -8℃ and -12℃. The schematic diagram of the whole device is shown in Fig. 2. According to the voltage-transmittance (V-T) curve, the maximum transmittance (T max ), minimum transmittance (T min ), threshold voltage (Vth), and saturation voltage (Vsat) of the sample can be obtained. The threshold voltage (Vth) is the minimum voltage required to produce a significant change in transmittance, corresponding to the voltage when the transmittance is T 10% ; the saturation voltage (Vsat) for the maximum transmittance of the voltage required, corresponding to the transmittance of T 90% of the voltage. T 10% is defined as T 10% =(T max -T min )×10%+T min , and T 90% is defined as T 90% =(T max -T min )×90%+T min . The rise time τ on at room temperature is the time corresponding to the rise in transmittance from T 10% to T 90% after applying the electric field. The decay time τ off is the time corresponding to the drop in transmittance from T 90% to T 10% after removing the electric field. The off-state recovery time t at low temperature is defined as the time from the moment of removing the electric field to the transmittance of T 10% . A blank point inside the symbol in the figure indicates that the transmittance has not decreased to T 10% . The ratio of optimization O at each temperature is defined as O = Δt/t, where Δt is the difference between the maximum change in the recovery time after doping with Span-80 and the recovery time when undoped. 3 Results and Discussion 3.1 Analysis at room temperature Figure 3 shows the POM diagrams of the samples between orthogonal polarizers. When no voltage is applied, the liquid crystal molecules are disordered. Due to the birefringence of liquid crystal, the light can pass through the orthogonal polarizers and the field of view is bright. As the voltage increases, the liquid crystal molecules slowly align vertically, and the birefringence phenomenon gradually disappears. The light cannot pass through the orthogonal polarizer, and the field of view gradually becomes dark. Comparing all the samples, the undoped sample has a brighter field of view under the same voltage, indicating that its driving voltage is higher. Figure 4 (a) shows the voltage dependence of the transmittance of each sample at room temperature. It can be seen that the transmittance of all samples reaches the saturation level with the increase of the applied voltage. Span-80 doping also affects the threshold voltage and saturation voltage of the sample, and the trend is shown in Fig. 4 (b). Compared with the undoped sample, the threshold voltage and saturation voltage of PDLC doped with Span-80 are reduced. The τ on of each sample decreases sequentially, and τ off increases first and then decreases. This may be due to the fact that the addition of Span-80 can reduce the interaction between liquid crystals and polymers. 3.2 Analysis at low temperatures Figure 5 (a)(b) shows the electro-optical properties of undoped PDLC at various temperatures. From the electro-optical curves of each sample, the transmittance of the samples all reach the saturation level with the increase of the applied voltage; the electro-optical curves are gradually moving right with the decrease of the temperature. The recovery time is very significantly affected by temperature, so we focus on discussing the recovery time at low temperatures. With temperature decreasing, the driving voltage and the recovery time increases gradually. Figure 5 (c) is a physical diagram of the undoped PDLC during the process of removing the electric field at 0 ℃. It can be seen from the figure that PDLC exhibits scattering state when no electric field is applied, and presents transparent state when electric field is applied. The sample slowly transforms from transparent state to scattering state after removing the electric field. The samples with four doping concentrations were placed at low temperatures for experiment and discuss respectively. Figure 6 (a)-(h) shows the electro-optical properties of Span-80 doped PDLC at low temperatures. From the electro-optical curves of samples in Fig. 6 (a)(c)(e)(g), it can be seen that the transmittance of each sample reaches the saturation level of about 80% with the increase of applied voltage. Furthermore, as the decrease of temperature, the electro-optical curve gradually moves right, which indicates that the driving voltage of the sample increases with the decrease of temperature. The driving voltage is shown in Fig. 6 (b)(d)(f)(h), which changes with temperature. When the temperature decreases, the recovery time of each sample becomes longer. Comparing all the samples, it can be seen that the threshold voltage and the saturation voltage of the doped sample are relatively lower than those of the undoped sample. This indicates that surfactant doping has played a certain role in reducing the threshold voltage and the saturation voltage. The recovery times of the samples with the four doping concentrations at each temperature were compared, from which a sample with the largest amount of recovery time optimization at each temperature was selected, as shown in Fig. 7 . It can be seen from the Fig. 7 , Span-80 doped PDLC cannot shorten the recovery time at the temperature of 8℃; at the temperatures of -8℃ and − 12℃, the optimization of the recovery time is less than 20%; at the temperatures of 0℃ and ± 4℃, the optimization is over 30%. According to the experimental results, Span-80 doping in the range of -4℃-4℃ can shorten the recovery time of PDLC. The nanoparticles added to PDLC are not uniformly distributed, such as the introduction of silica nanoparticles (SNPs) into PDLC[24]. Most of the SNPs and their aggregates are randomly distributed inside the polymer matrix. However, some SNPs are trapped by defects and at the polymer-liquid crystal interface [25]. It has also been shown that nanoparticles aggregate at the poles of bipolar droplets [26]. From the theoretical aspect, Span-80 as a surfactant is an amphiphilic molecule with lipophilic and hydrophilic groups. When the surfactant is present in water, the lipophilic groups shrink their tails together to avoid contact with water, while the hydrophilic groups are exposed to form micelles. Since both liquid crystal and polymer are oleophilic, the hydroxyl group, which is the hydrophilic end, is repelled by both liquid crystal and polymer. Span-80 will eventually stabilize at the interface between the polymer and the liquid crystal. Ju Yeon Woo et al. added octanoic acid as a surfactant into the holographic polymer dispersed liquid crystal system [27]. They concluded that octanoic acid encapsulates liquid crystal droplets during phase separation and that surfactants can modify the phase interface interaction. Since the rise time mainly depends on the applied voltage, it cannot obviously reflect the change of the interaction between the polymer and the liquid crystal. Therefore, the recovery time is the main object of experimental investigation and an important basis for modelling. From the experimental results, the recovery time of the material is prolonged as the temperature decreases, as shown in Fig. 6 (b)(d)(f)(h). On the one hand, the viscosity coefficient of the liquid crystal increases, resulting in a longer time for the liquid crystal to rotate. On the other hand, there is a change in the interaction between liquid crystal and polymer matrix. Specifically, it is the presence of an impediment to rotation between the liquid crystal and the polymer, which exists as a resistance both during the liquid crystal driving process and the recovery process. This is analogous to macroscopically existing friction, i.e., friction exists as resistance regardless of the direction of motion of the object. The prolongation of the recovery time at low temperatures can be explained by the increase of this resistance. When Span-80 is introduced into the PDLC system, it distributes at the interface between the polymer and the liquid crystal. The introduction of Span-80 is equivalent to the addition of lubricant to the system. During the rotation of the liquid crystal, the Span-80 acts as a lubricant and reduces the resistance to shorten the recovery time. In summary, a ball lubrication model can explain this phenomenon of Span-80 shortening the recovery time of PDLC at low temperatures. The schematic diagram of the model is shown in Fig. 8 (b). As shown in Fig. 7 , three temperatures of 4°C, 0°C and − 4°C at which the recovery time is optimized more significantly by Span-80 were chosen to analyze the relevant phenomena using our model. At these three temperatures, the PDLC driving voltage is lower and the recovery time is shorter for a doping concentration of 1.5 wt.% of Span-80. The curve of its comparison with undoped PDLC is shown in Fig. 9 . Using the model, it can be explained that the surfactant weakened the force that prevented the rotation of liquid crystal molecules. It results in less time and lower voltage required for the rotation of liquid crystal molecules. 4 Conclusion In this paper, the effect of Span-80 doping concentration on the electro-optical properties of PDLC prepared by polymerization induced phase separation method was investigated. Through discussion from the perspective of room temperature and low temperature, it is found that Span-80 doping can reduce the threshold voltage and saturation voltage of PDLC. For the aspect of shortening the recovery time, the most suitable temperature for Span-80 doping is about 0°C. In this temperature range of -4℃ to 4℃, the minimum driving voltage and the fastest recovery time is at 1.5 wt.% of Span-80 doping concentration. Further, based on the mechanism that the Span-80 doping can shorten the recovery time, the ball lubrication model is proposed, which is believed that doping surfactant will weaken the resistance of liquid crystal rotation. The results from the ideal model are consistent with the experimental results. This study provides a new direction for the preparation of PDLC films with a wide working temperature range such as smart windows of automobiles and exterior walls of buildings and other outdoor applications. Declarations Authors’ contributions All the authors were involved in the preparation of the manuscript. All the authors have read and approved the final manuscript. D isclosure statement No potential conflict of interest was reported by the author(s). Acknowledgements This work was supported by the Innovation Method Fund of China [Grant Number 2020IM020600]; the Industry-University Cooperative Education Project of Ministry of Education of China [Grant Number 202102026001]; the Research Projects of Undergraduate Education and Teaching Reform in Hebei University of Technology [Grant Number 201903006]; the Higher Education Teaching Research Program of Hebei Society of Higher Education [Grant Number GJXH2019-019]; and the Natural Science Foundation of China [Grant Number 51805142]. References S. M. Guo et al (2017) Preparation of a Thermally Light-Transmittance-Controllable Film from a Coexistent System of Polymer-Dispersed and Polymer-Stabilized Liquid Crystals. ACS Appl Mater Inter 9(3):2942-2947. R. R. Deshmukh and M. K. Malik (2013) Effect of dichroic dye on phase separation kinetics and electro-optical characteristics of polymer dispersed liquid crystals. J Phys Chem Solids 74(2):215-224. C. P. Ganea, D. Manaila-Maximean and V. 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Supplementary Files GraphicalAbstract.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 20 Apr, 2025 Reviews received at journal 13 Apr, 2025 Reviews received at journal 12 Apr, 2025 Reviews received at journal 12 Apr, 2025 Reviewers agreed at journal 09 Apr, 2025 Reviewers agreed at journal 04 Apr, 2025 Reviewers agreed at journal 03 Apr, 2025 Reviewers agreed at journal 03 Apr, 2025 Reviewers invited by journal 03 Apr, 2025 Editor assigned by journal 07 Mar, 2025 Submission checks completed at journal 07 Mar, 2025 First submitted to journal 27 Feb, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6121841","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":425481934,"identity":"64bf0279-881f-41c9-9da3-88e4ad5d9d7d","order_by":0,"name":"Wenya Gai","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Wenya","middleName":"","lastName":"Gai","suffix":""},{"id":425481935,"identity":"23b5cefa-c377-4d65-a01b-68350e518229","order_by":1,"name":"Ran An","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Ran","middleName":"","lastName":"An","suffix":""},{"id":425481936,"identity":"ee46ff2d-9b55-46e2-97e5-4dfcd5f7db59","order_by":2,"name":"Yue Han","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yue","middleName":"","lastName":"Han","suffix":""},{"id":425481937,"identity":"c76d7bf6-3580-45a7-a80a-ff9be7c1866f","order_by":3,"name":"Jiabo Zhang","email":"","orcid":"","institution":"Arizona College of Technology at Hebei University of Technology, Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Jiabo","middleName":"","lastName":"Zhang","suffix":""},{"id":425481938,"identity":"3ee59c73-fb29-4882-bbdb-bc779b33c0f2","order_by":4,"name":"Hui Zhang","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Hui","middleName":"","lastName":"Zhang","suffix":""},{"id":425481939,"identity":"7a317b12-c1e1-47dc-9c9f-cf94a23f6471","order_by":5,"name":"Guili Zheng","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Guili","middleName":"","lastName":"Zheng","suffix":""},{"id":425481940,"identity":"7449bd25-8336-4172-8cc2-412a1d60e6d1","order_by":6,"name":"Yanjun Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4UlEQVRIiWNgGAWjYHCC9A8JP2wSGCTAHGaitKQxPOxJA2lhbCBWCxvjA7bDJGiRn5Hw7EECz/k8fuke8wcMFdaJDexnD+DVwjgjId0gweJ2seScM4YNDGfSExt48hLwamGWSEiQSOC5nbjhRo5hA2Pb4cQGCR4D/B4Ba2E7l7gfrOUfEVp4JBLSgFoOJG6QAGlpIEKLBM+DZIPEnuTEGXeOFc5IOJZu3MaTg1+LfHtO4sMfP+wS+2c3b/jwocZatp/9DH4tDAI5CQgOiMmGXz0Q8B8/QFDNKBgFo2AUjHAAAGTPSgwBpV1LAAAAAElFTkSuQmCC","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Yanjun","middleName":"","lastName":"Zhang","suffix":""},{"id":425481941,"identity":"69164e2e-9b10-4c59-91f2-835ffcfb8019","order_by":7,"name":"Zhiguang Li","email":"","orcid":"","institution":"Hebei University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Zhiguang","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2025-02-27 14:23:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6121841/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6121841/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":78146286,"identity":"c749edb7-fc38-4013-9a5f-412df736baff","added_by":"auto","created_at":"2025-03-10 10:59:52","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":86065,"visible":true,"origin":"","legend":"\u003cp\u003eThe preparation process and working mechanism of PDLC. (a) The fabrication procedures of PDLC. (b) Light-scattering state and (c) Transparent state when power-on and power-off\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/8ab62656753657d61a8cc2d2.png"},{"id":78147015,"identity":"fad26414-ba0c-4c68-bb28-a228057d7ff3","added_by":"auto","created_at":"2025-03-10 11:07:52","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":49567,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental setup for the electro-optic characterization\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/e532edbbcf6aa8f2c68ea0d7.png"},{"id":78146289,"identity":"6894cb12-659c-4855-9f3f-73d66f3cb586","added_by":"auto","created_at":"2025-03-10 10:59:52","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":624410,"visible":true,"origin":"","legend":"\u003cp\u003ePOM diagrams at different voltages of each sample\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/adbe1c23d10532f7572bdaf6.png"},{"id":78146293,"identity":"d6c4b48d-bc75-4098-8389-951096c6ad57","added_by":"auto","created_at":"2025-03-10 10:59:52","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":26125,"visible":true,"origin":"","legend":"\u003cp\u003e\u0026nbsp;(a) The transmittance curve with voltage, (b) the threshold voltage (Vth), saturation voltage (Vsat), rise time (τ\u003csub\u003eon\u003c/sub\u003e) and decay time (τ\u003csub\u003eoff\u003c/sub\u003e) of each sample at room temperature\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/08d362725b741fcdd8510ecb.png"},{"id":78146320,"identity":"37025137-0b54-41ab-a74c-a58609324e91","added_by":"auto","created_at":"2025-03-10 10:59:55","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":140196,"visible":true,"origin":"","legend":"\u003cp\u003e(a) The transmittance curve with voltage, (b) the threshold voltage (Vth), saturation voltage (Vsat) and recovery time (t) of undoped PDLC at low temperatures. (c) Physical diagram of undoped PDLC at 0 ℃ when power-off\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/eafa0c928c6ab6bfd469009e.png"},{"id":78147017,"identity":"031fce03-661b-4e7b-9346-8944b6da5feb","added_by":"auto","created_at":"2025-03-10 11:07:52","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":56605,"visible":true,"origin":"","legend":"\u003cp\u003eThe transmittance curve with voltage of (a) 0.5 wt.% (c)1.0 wt.% (e) 1.5wt.% (g) 2.0 wt.% Span-80 doped PDLC at low temperatures. The threshold voltage (Vth), saturation voltage (Vsat) and recovery time (t) of (b) 0.5 wt.% (d)1.0 wt.% (f) 1.5wt.% (h) 2.0 wt.% Span-80 doped PDLC at low temperatures\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/f613fb61ef92a6aa4606afab.png"},{"id":78147022,"identity":"2c2eb0e0-0871-4b59-91af-3ceea5c653d5","added_by":"auto","created_at":"2025-03-10 11:07:53","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":15804,"visible":true,"origin":"","legend":"\u003cp\u003eThe ratio of optimization at various low temperatures\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/a9dc3f3b65c90a5a77b21f2b.png"},{"id":78148516,"identity":"1184a77c-bf9f-4c11-8250-6ee8cff56424","added_by":"auto","created_at":"2025-03-10 11:24:04","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":57725,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Ball-and-stick model of Span-80, (b)The model to describe the distribution of span-80 in the PDLC\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/14fa134b179c7a942bdbd9ff.png"},{"id":78146296,"identity":"a7011893-69b2-4073-8e49-f8bd90f830d5","added_by":"auto","created_at":"2025-03-10 10:59:52","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":44671,"visible":true,"origin":"","legend":"\u003cp\u003eThe transmittance curve with voltage of undoped PDLC and 1.5 wt.% Span-80 doped PDLC at (a) 4℃ (c) 0℃ (e) -4℃. The threshold voltage (Vth), saturation voltage (Vsat) and recovery time (t) of undoped PDLC and 1.5 wt.% Span-80 doped PDLC at (b) 4℃ (d) 0℃ (f) -4℃\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/489f6383318279d894e8ddee.png"},{"id":78148794,"identity":"cecd820b-ff83-4376-b281-c1f88ee0b730","added_by":"auto","created_at":"2025-03-10 11:24:15","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1506283,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/2403a414-eb03-4b38-847c-df7816240020.pdf"},{"id":78146290,"identity":"6ed411cd-5988-45a1-bc13-c9f4f3f4a78d","added_by":"auto","created_at":"2025-03-10 10:59:52","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":247458,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.docx","url":"https://assets-eu.researchsquare.com/files/rs-6121841/v1/8f4ecd014554992e0175fc16.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Analysis of electro-optical properties of surfactant doped polymer dispersed liquid crystal","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eLiquid crystal/polymer composites have been a subject of great interest and exploration in recent years. This composite material consists of two parts: polymer and liquid crystal. Polymer dispersed liquid crystal (PDLC), polymer network liquid crystal (PNLC) and polymer stabilized liquid crystal (PSLC) are the three primary categories of liquid crystal/polymer composites based on the different concentration of polymer monomer [1\u0026ndash;4]. Polymer concentration is more than 30% results in the formation of polymer dispersed liquid crystals. That is, the liquid crystals are randomly dispersed in the polymer matrix in the form of microdroplets. When no electric field is applied, due to the refractive index mismatch between the liquid crystal and the polymer matrix, the PDLC film presents scattering state, i.e., the opaque state. After applying an electric field, the refractive indices of the liquid crystal and polymer match, and the PDLC film presents transparent state. Since PDLC can modulate light without polarizers and orientation layers, it not only reduces the cost but also simplifies the design, making it widely applicable, such as smart windows, sensors, displays, and so on [5\u0026ndash;14]. Current researches mainly focus on reducing the driving voltage, shortening the response time. Nanoparticles doped PDLC is a good direction to solve the problem. The nanoparticles added to PDLC are mainly divided into three categories: oxide nanoparticles (e.g., SiO2, BaTiO3, ITO, etc.), quantum dot nanoparticles (e.g., CdS QD, CdSeS/ZnS QD, ZnCdSeS/ZnS QD, etc.) and metal nanoparticles (e.g., Ag, Zn, Au, etc.). Nanoscale doping of graphene, carbon nanotubes, dyes, cellulose, etc. is also common [15\u0026ndash;16]. The above work is carried out to improve the electro-optical properties of PDLC at room temperature. However, in applications such as smart windows of automobiles and exterior walls of buildings, PDLC films might experience harsh temperature conditions. When PDLC films are in low temperature conditions, the driving voltage increases and the switching speed between scattering state and transparent state becomes slow. The study of the improvement of their performance at low temperatures becomes particularly important. Xu Jianjun et al. performed a series of studies on PDLC with wide working temperature range. Firstly, researchers have explored ways to improve the performance of PDLC films at high and low temperatures by using liquid crystals with a wide temperature range, monomers and cross-linking agents [17]. The results show that the PDLC films prepared with hexyl acrylate as monomer and 1, 4-butanediol diacrylate as cross-linking agent have excellent electro-optical properties and can work in a wide temperature range. Secondly, polymer dispersed liquid crystal films with good electro-optical properties and wide working temperature range were prepared by optimizing the curing temperature [18]. It was found that when the polymerization temperature is at the clearing point of polymer/liquid crystal mixture, the films have better electro-optical properties and higher contrast ratio (CR) at high temperatures, and faster rise time and decay time at low temperatures. Thirdly, the incorporation of fluorinated liquid crystal into the liquid crystal, which can successfully reduce the driving voltage of the PDLC films at sub-zero temperature, but the contrast ratio at high temperatures is reduced [19]. In all three studies, cross-linking agents and liquid crystals with a wide temperature range were used. The use of cross-linking agents allows the linear molecules to interconnect to form a mesh structure, which improves the strength and elasticity of the polymer material. The wide temperature range of liquid crystals allows PDLC to have a wide working temperature range.\u003c/p\u003e \u003cp\u003ePDLC made from prepolymers is not easy to work over a wide temperature range. However, it can be seen from the above discussion that doping can improve the electro-optical properties of PDLC at low temperatures, which requires that the doped substances remain stable at low temperatures. In production and life, products used in low temperature are added surfactants to achieve the purpose of anti-freezing [20\u0026ndash;23], then the use of surfactants for doping of PDLC is a new method.\u003c/p\u003e \u003cp\u003eThis article introduces the surfactant Span-80 into PDLC and studies its effect on the electro-optical properties of PDLC at different temperatures. The temperature range suitable for the working of Span-80 is selected by experiments, and the experimental rules are explained by using the ideal model of ball lubrication.\u003c/p\u003e"},{"header":"2 Experiments","content":"\u003ch2\u003e2.1 Materials\u003c/h2\u003e\n\u003cp\u003eThe liquid crystal used in this experiment was a positive nematic liquid crystals PDLC-005 (\u003cem\u003en\u003c/em\u003e\u003csub\u003ee\u003c/sub\u003e=1.745, \u003cem\u003en\u003c/em\u003e\u003csub\u003eo\u003c/sub\u003e=1.52, \u0026Delta;\u003cem\u003en\u003c/em\u003e=0.225, T\u003cem\u003e\u003csub\u003eCr-N\u003c/sub\u003e\u003c/em\u003e﹤-30℃, T\u003cem\u003e\u003csub\u003eN-I\u003c/sub\u003e\u003c/em\u003e =109℃), from Luquan Liquid Crystal Factory. Monofunctional reactive monomers Isononyl Acrylate (INAA), Isobornyl Acrylate (IBOA), Isobornyl Methacrylate (IBOMA), and photo-initiator 1-Hydroxy-Cyclohexylphenyl-Ketone (PI 184) were provided by Changxing Chemical Materials Co., LTD. Prepolymer CN131 was purchased from Sadoma Chemical Co., LTD. Spacer with a diameter of 10\u0026mu;m was provided by Suzhou Nanno Technology Co., LTD. Surfactant Span-80 in this paper was purchased from Xingtai Lanxing Auxiliary Factory. The formulation compositions of the undoped PDLC were given in Table 1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e \u0026nbsp;The formulation compositions of the undoped PDLC (weight percent)\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\" style=\"width: 336px;\"\u003e\n \u003cp\u003ePolymer\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" style=\"width: 212px;\"\u003e\n \u003cp\u003ePolymer: Liquid Crystal\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eINAA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003eIBOA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003eIBOMA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003eCN131\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 72px;\"\u003e\n \u003cp\u003ePI 184\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 60px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 68px;\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 76px;\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 72px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 212px;\"\u003e\n \u003cp\u003e40:60\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003ch2\u003e2.2 Sample Preparation\u003c/h2\u003e\n\u003cp\u003eIn this experiment, PDLC was prepared by polymerization induced phase separation (PIPS). To study the influence of Span-80 in the PDLC, the mass ratio of polymer to liquid crystal was kept constant (Polymer: Liquid Crystal=40:60) and the concentration of Span-80 was varied (\u0026le;2 wt.%). Samples were prepared by doping Span-80 in different concentrations into PDLC (0.5 wt.%, 1.0 wt.%, 1.5 wt.%, 2.0 wt.%). For the comparison of the results, an undoped PDLC sample was also prepared. Firstly, the polymer and the liquid crystal were properly mixed in a vial, which was stirred for 15 minutes to obtain a homogeneous solution. The surfactant Span-80 was added to the homogeneous solution and then continued stirring for 15 minutes. Then the conductive glass coated with indium tin oxide (ITO) on the inner surface was cleaned with anhydrous ethanol, and a small number of spacers were uniformly sprinkled onto the glass surface. Afterwards, 4\u0026mu;l of uniform solution was dropped onto the glass with a pipette gun, and slowly covered with another piece of glass staggered 1cm apart to make a liquid crystal cell with a square area of about 2 cm \u0026times; 2 cm. Finally, the preparation was exposed under UV light (intensity of 12mW/cm\u003csup\u003e2\u003c/sup\u003e) for 3 minutes at room temperature, as shown in Fig. 1(a). When no electric field was applied, the disordered liquid crystal droplets were dispersed in the polymer matrix and the film exhibited the scattering state shown in Fig. 1(b). When the electric field was applied, the liquid crystal droplets were ordered along the direction of the electric field, and the film presented the transparent state, as shown in Fig. 1(c).\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003e2.3 Characterizations\u003c/h2\u003e\n\u003cp\u003eA sample was placed under the orthogonal polarizer (OLYMPUS BX51) to obtain the POM image. The electro-optical properties of the prepared samples were carried out by constructing an optical circuit, in which a He-Ne laser (\u003cem\u003e\u0026lambda;\u003c/em\u003e = 632.8 nm) was used as the incident light source. The light was passed through the attenuator and the sample in turn, and finally received by the photodetector. The oscilloscope generated a square wave signal with a frequency of 1kHz, which was amplified by an amplifier and was applied to the sample. The electro-optical properties at low temperatures were cooled by a temperature control device. The temperatures for the experimental steps were 8℃, 4℃, 0℃, -4℃, -8℃ and -12℃. The schematic diagram of the whole device is shown in Fig. 2.\u003c/p\u003e\n\u003cp\u003eAccording to the voltage-transmittance (V-T) curve, the maximum transmittance (T\u003csub\u003emax\u003c/sub\u003e), minimum transmittance (T\u003csub\u003emin\u003c/sub\u003e), threshold voltage (Vth), and saturation voltage (Vsat) of the sample can be obtained. The threshold voltage (Vth) is the minimum voltage required to produce a significant change in transmittance, corresponding to the voltage when the transmittance is T\u003csub\u003e10%\u003c/sub\u003e; the saturation voltage (Vsat) for the maximum transmittance of the voltage required, corresponding to the transmittance of T\u003csub\u003e90%\u003c/sub\u003e of the voltage. T\u003csub\u003e10%\u003c/sub\u003e is defined as T\u003csub\u003e10%\u003c/sub\u003e=(T\u003csub\u003emax\u003c/sub\u003e-T\u003csub\u003emin\u003c/sub\u003e)\u0026times;10%+T\u003csub\u003emin\u003c/sub\u003e , and T\u003csub\u003e90%\u003c/sub\u003e is defined as T\u003csub\u003e90%\u003c/sub\u003e=(T\u003csub\u003emax\u003c/sub\u003e-T\u003csub\u003emin\u003c/sub\u003e)\u0026times;90%+T\u003csub\u003emin\u003c/sub\u003e. The rise time \u0026tau;\u003csub\u003eon\u003c/sub\u003e at room temperature is the time corresponding to the rise in transmittance from T\u003csub\u003e10%\u003c/sub\u003e to T\u003csub\u003e90%\u003c/sub\u003e after applying the electric field. The decay time \u0026tau;\u003csub\u003eoff\u003c/sub\u003e is the time corresponding to the drop in transmittance from T\u003csub\u003e90%\u003c/sub\u003e to T\u003csub\u003e10%\u003c/sub\u003e after removing the electric field. The off-state recovery time t at low temperature is defined as the time from the moment of removing the electric field to the transmittance of T\u003csub\u003e10%\u003c/sub\u003e. A blank point inside the symbol in the figure indicates that the transmittance has not decreased to T\u003csub\u003e10%\u003c/sub\u003e. The ratio of optimization O at each temperature is defined as O = \u0026Delta;t/t, where \u0026Delta;t is the difference between the maximum change in the recovery time after doping with Span-80 and the recovery time when undoped.\u003c/p\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Analysis at room temperature\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the POM diagrams of the samples between orthogonal polarizers. When no voltage is applied, the liquid crystal molecules are disordered. Due to the birefringence of liquid crystal, the light can pass through the orthogonal polarizers and the field of view is bright. As the voltage increases, the liquid crystal molecules slowly align vertically, and the birefringence phenomenon gradually disappears. The light cannot pass through the orthogonal polarizer, and the field of view gradually becomes dark. Comparing all the samples, the undoped sample has a brighter field of view under the same voltage, indicating that its driving voltage is higher.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a) shows the voltage dependence of the transmittance of each sample at room temperature. It can be seen that the transmittance of all samples reaches the saturation level with the increase of the applied voltage. Span-80 doping also affects the threshold voltage and saturation voltage of the sample, and the trend is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b). Compared with the undoped sample, the threshold voltage and saturation voltage of PDLC doped with Span-80 are reduced. The τ\u003csub\u003eon\u003c/sub\u003e of each sample decreases sequentially, and τ\u003csub\u003eoff\u003c/sub\u003e increases first and then decreases. This may be due to the fact that the addition of Span-80 can reduce the interaction between liquid crystals and polymers.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Analysis at low temperatures\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a)(b) shows the electro-optical properties of undoped PDLC at various temperatures. From the electro-optical curves of each sample, the transmittance of the samples all reach the saturation level with the increase of the applied voltage; the electro-optical curves are gradually moving right with the decrease of the temperature. The recovery time is very significantly affected by temperature, so we focus on discussing the recovery time at low temperatures. With temperature decreasing, the driving voltage and the recovery time increases gradually. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c) is a physical diagram of the undoped PDLC during the process of removing the electric field at 0 ℃. It can be seen from the figure that PDLC exhibits scattering state when no electric field is applied, and presents transparent state when electric field is applied. The sample slowly transforms from transparent state to scattering state after removing the electric field.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe samples with four doping concentrations were placed at low temperatures for experiment and discuss respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a)-(h) shows the electro-optical properties of Span-80 doped PDLC at low temperatures. From the electro-optical curves of samples in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a)(c)(e)(g), it can be seen that the transmittance of each sample reaches the saturation level of about 80% with the increase of applied voltage. Furthermore, as the decrease of temperature, the electro-optical curve gradually moves right, which indicates that the driving voltage of the sample increases with the decrease of temperature. The driving voltage is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e (b)(d)(f)(h), which changes with temperature. When the temperature decreases, the recovery time of each sample becomes longer. Comparing all the samples, it can be seen that the threshold voltage and the saturation voltage of the doped sample are relatively lower than those of the undoped sample. This indicates that surfactant doping has played a certain role in reducing the threshold voltage and the saturation voltage.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe recovery times of the samples with the four doping concentrations at each temperature were compared, from which a sample with the largest amount of recovery time optimization at each temperature was selected, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. It can be seen from the Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, Span-80 doped PDLC cannot shorten the recovery time at the temperature of 8℃; at the temperatures of -8℃ and \u0026minus;\u0026thinsp;12℃, the optimization of the recovery time is less than 20%; at the temperatures of 0℃ and \u0026plusmn;\u0026thinsp;4℃, the optimization is over 30%. According to the experimental results, Span-80 doping in the range of -4℃-4℃ can shorten the recovery time of PDLC.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe nanoparticles added to PDLC are not uniformly distributed, such as the introduction of silica nanoparticles (SNPs) into PDLC[24]. Most of the SNPs and their aggregates are randomly distributed inside the polymer matrix. However, some SNPs are trapped by defects and at the polymer-liquid crystal interface [25]. It has also been shown that nanoparticles aggregate at the poles of bipolar droplets [26]. From the theoretical aspect, Span-80 as a surfactant is an amphiphilic molecule with lipophilic and hydrophilic groups. When the surfactant is present in water, the lipophilic groups shrink their tails together to avoid contact with water, while the hydrophilic groups are exposed to form micelles. Since both liquid crystal and polymer are oleophilic, the hydroxyl group, which is the hydrophilic end, is repelled by both liquid crystal and polymer. Span-80 will eventually stabilize at the interface between the polymer and the liquid crystal. Ju Yeon Woo et al. added octanoic acid as a surfactant into the holographic polymer dispersed liquid crystal system [27]. They concluded that octanoic acid encapsulates liquid crystal droplets during phase separation and that surfactants can modify the phase interface interaction.\u003c/p\u003e \u003cp\u003eSince the rise time mainly depends on the applied voltage, it cannot obviously reflect the change of the interaction between the polymer and the liquid crystal. Therefore, the recovery time is the main object of experimental investigation and an important basis for modelling. From the experimental results, the recovery time of the material is prolonged as the temperature decreases, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(b)(d)(f)(h). On the one hand, the viscosity coefficient of the liquid crystal increases, resulting in a longer time for the liquid crystal to rotate. On the other hand, there is a change in the interaction between liquid crystal and polymer matrix. Specifically, it is the presence of an impediment to rotation between the liquid crystal and the polymer, which exists as a resistance both during the liquid crystal driving process and the recovery process. This is analogous to macroscopically existing friction, i.e., friction exists as resistance regardless of the direction of motion of the object. The prolongation of the recovery time at low temperatures can be explained by the increase of this resistance. When Span-80 is introduced into the PDLC system, it distributes at the interface between the polymer and the liquid crystal. The introduction of Span-80 is equivalent to the addition of lubricant to the system. During the rotation of the liquid crystal, the Span-80 acts as a lubricant and reduces the resistance to shorten the recovery time. In summary, a ball lubrication model can explain this phenomenon of Span-80 shortening the recovery time of PDLC at low temperatures. The schematic diagram of the model is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, three temperatures of 4\u0026deg;C, 0\u0026deg;C and \u0026minus;\u0026thinsp;4\u0026deg;C at which the recovery time is optimized more significantly by Span-80 were chosen to analyze the relevant phenomena using our model. At these three temperatures, the PDLC driving voltage is lower and the recovery time is shorter for a doping concentration of 1.5 wt.% of Span-80. The curve of its comparison with undoped PDLC is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e. Using the model, it can be explained that the surfactant weakened the force that prevented the rotation of liquid crystal molecules. It results in less time and lower voltage required for the rotation of liquid crystal molecules.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eIn this paper, the effect of Span-80 doping concentration on the electro-optical properties of PDLC prepared by polymerization induced phase separation method was investigated. Through discussion from the perspective of room temperature and low temperature, it is found that Span-80 doping can reduce the threshold voltage and saturation voltage of PDLC. For the aspect of shortening the recovery time, the most suitable temperature for Span-80 doping is about 0\u0026deg;C. In this temperature range of -4℃ to 4℃, the minimum driving voltage and the fastest recovery time is at 1.5 wt.% of Span-80 doping concentration. Further, based on the mechanism that the Span-80 doping can shorten the recovery time, the ball lubrication model is proposed, which is believed that doping surfactant will weaken the resistance of liquid crystal rotation. The results from the ideal model are consistent with the experimental results. This study provides a new direction for the preparation of PDLC films with a wide working temperature range such as smart windows of automobiles and exterior walls of buildings and other outdoor applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthors’ contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors were involved in the preparation of the manuscript. All the authors have read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eD\u003c/strong\u003e\u003cstrong\u003eisclosure statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo potential conflict of interest was reported by the author(s).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Innovation Method Fund of China [Grant Number 2020IM020600]; the Industry-University Cooperative Education Project of Ministry of Education of China [Grant Number 202102026001]; the Research Projects of Undergraduate Education and Teaching Reform in Hebei University of Technology [Grant Number 201903006]; the Higher Education Teaching Research Program of Hebei Society of Higher Education [Grant Number GJXH2019-019]; and the Natural Science Foundation of China [Grant Number 51805142].\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eS. M. Guo et al (2017) Preparation of a Thermally Light-Transmittance-Controllable Film from a Coexistent System of Polymer-Dispersed and Polymer-Stabilized Liquid Crystals. ACS Appl Mater Inter 9(3):2942-2947.\u003c/li\u003e\n \u003cli\u003eR. R. Deshmukh and M. K. Malik (2013) Effect of dichroic dye on phase separation kinetics and electro-optical characteristics of polymer dispersed liquid crystals. J Phys Chem Solids 74(2):215-224.\u003c/li\u003e\n \u003cli\u003eC. P. Ganea, D. Manaila-Maximean and V. C\u0026icirc;rcu (2020) Dielectric investigations on carbon nanotubes doped polymer dispersed liquid crystal films. Eur Phys J Plus 135(10):737.\u003c/li\u003e\n \u003cli\u003eM. S. Zhang et al (2022) Effect of different monomers on the electro-optical properties of reverse-mode polymer stabilized liquid crystal. J Mol Liq 363.\u003c/li\u003e\n \u003cli\u003eS. 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Rahimi et al (2015) Nanoparticle self-assembly at the interface of liquid crystal droplets. P Natl Acad Sci USA 112(17).\u003c/li\u003e\n \u003cli\u003eJ. Y. Woo and B. K. Kim (2007) Surfactant effects on morphology and switching of holographic PDLCs based on polyurethane acrylates. Chemphyschem 8,(1):175-180.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"colloid-and-polymer-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Colloid and Polymer Science](https://www.springer.com/journal/396) ","snPcode":"396","submissionUrl":"https://mc.manuscriptcentral.com/cps","title":"Colloid and Polymer Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"polymer dispersed liquid crystal, low temperature, surfactant, electro-optical properties","lastPublishedDoi":"10.21203/rs.3.rs-6121841/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6121841/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe narrow working temperature range is one of the significant factors limiting the wide applications of polymer dispersed liquid crystal (PDLC). In this paper, we have prepared a surfactant (Span-80) doped PDLC. The different concentration of Span-80 has a significant impact on the electro-optical properties of PDLC at different temperatures. Based on the experimental results that doping of Span-80 can reduce the driving voltage and shorten the recovery time of PDLC at low temperatures, a ball lubrication model has been proposed. The results from the ideal model are consistent with the experimental results.\u003c/p\u003e","manuscriptTitle":"Analysis of electro-optical properties of surfactant doped polymer dispersed liquid crystal","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-10 10:59:47","doi":"10.21203/rs.3.rs-6121841/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-04-21T01:57:27+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-13T17:35:11+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-12T15:09:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-12T06:37:32+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80377638102266924426446624527341793081","date":"2025-04-09T15:30:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"41293103853753355323276438601729442160","date":"2025-04-04T15:09:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"241300837288535915387397286487973554720","date":"2025-04-04T03:38:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"105647190809538157591229578258707763289","date":"2025-04-03T16:25:21+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-03T16:01:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-03-07T08:37:47+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-03-07T08:33:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"Colloid and Polymer Science","date":"2025-02-27T14:13:11+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"colloid-and-polymer-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Colloid and Polymer Science](https://www.springer.com/journal/396) ","snPcode":"396","submissionUrl":"https://mc.manuscriptcentral.com/cps","title":"Colloid and Polymer Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"80ecea36-63e4-4a93-9ff9-1403e8e6c56f","owner":[],"postedDate":"March 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-06-09T08:23:05+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-10 10:59:47","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6121841","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6121841","identity":"rs-6121841","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}