Browsing by Author "Kemiklioglu E."
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Item Electro-optical properties of carbon nanotube-doped polymer-stabilised blue phase liquid crystal IPS cell(Taylor and Francis Ltd., 2016) Kemiklioglu E.; Chien L.-C.Carbon nanotube (CNT)-doped polymer-stabilised blue phase (PSBP) liquid crystal cells driven by an in-plane field are fabricated. Their electro-optical properties are investigated for both single-wall and multiwall CNT dopants. A small amount of CNT dopants in PSBP liquid crystals leads to broadening the blue phase temperature range over 42°C and stabilising the reflection wavelength against temperature changes. A lower Kerr constant and threshold voltage are obtained for a higher CNT concentration. Higher CNT concentrations lead to an increase in the elastic constant; therefore, the rise time of CNT-doped PSBP liquid crystal cells increases and decay time decreases. © 2016 Informa UK Limited, trading as Taylor & Francis Group.Item Effects of photoinitiator on electro-optical properties of polymerization-induced phase separation blue-phase liquid crystals(Springer New York LLC, 2017) Kemiklioglu E.; Chien L.-C.Abstract.: We have reported polymer-dispersed blue-phase (PDBP) liquid-crystal films via polymerization-induced phase separation. PDBP films are prepared by photochemical polymerization of curable crosslinking agent, monomer and blue-phase liquid crystal under an ultraviolet (UV) light. The influences of photoinitiator and weight ratio between monomer/crosslinking agent and blue phase on the electro-optical properties of PDBP liquid-crystal samples are investigated. The electro-optical (E-O) properties of PDBP films are determined in the top-down electro-optical cell. PDBP liquid-crystal films show good E-O properties with high contrast ratio and fast response time. Graphical abstract: [Figure not available: see fulltext.] © 2017, EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.Item Polymer encapsulated and stabilised blue-phase liquid crystal droplets(Taylor and Francis Ltd., 2017) Kemiklioglu E.; Chien L.-C.Polymer-encapsulated–polymer-stabilised blue-phase liquid crystals (LCs) are investigated. Encapsulated droplets are formed in a polyvinyl alcohol solution by emulsification, and blue-phase (BP) LCs in the droplets are stabilised via the polymerisation of reactive monomers to extend the BP temperature range. Polymer stabilised droplets are found to cause the expansion of the BP temperature range from 53°C to below 0°C. The effects of composition on droplet formation and the electro-optical behaviour and morphological properties of these droplets are reported. © 2016 Informa UK Limited, trading as Taylor & Francis Group.Item Effect of achiral halogen-substituted bent-core molecules on the blue phases(Elsevier B.V., 2018) Kemiklioglu E.; Chien L.-C.The effects of molecule structure and concentration of achiral bent-core molecules on the blue phase liquid crystal stabilization have been investigated. Blue phase mixtures are formed doping bent-core molecules and BP temperature range is able to widen doping bent-core molecules with different substituents. Bent-core molecules with different substituents are found to cause a decrement in the threshold and turn-on voltages of the bent-core doped blue phase liquid crystal samples, as a result of the difference in their molecular shape and dipole moments. Use of bent core LC as dopants for a blue phase LC mixture led to a reduction of the driving voltage by more than 50%. © 2018Item Investigation of mechanical behavior of polymer encapsulated liquid crystal composites(Institute of Physics Publishing, 2019) Kemiklioǧlu U.; Kemiklioglu E.In this study, the mechanical properties of polymer-liquid crystal composite films have been investigated as a function of changing polymer concentration. Nematic liquid crystal was encapsulated in waterborne polymer matrix of the polymer-liquid crystal composite films. The mechanical tests were carried out applying three- point bending tests on these films and the experimental results showed that the bending strength increases with the increasing polymer matrix concentration. The effects of the bending strength and polymer concentration on the morphological behaviors of these droplets were examined by using Scanning Electron Microscopy (SEM). The morphological and mechanical tests showed that the bending strength decreased with the increasing size and density of the waterborne encapsulated liquid crystal droplets. © 2019 IOP Publishing Ltd.Item The effect of the monomer functionality on the mechanical performance and polymer morphology of polymer stabilized blue phases(Elsevier Ltd, 2019) Kemiklioglu E.; Atik E.The mechanical behavior of the polymer stabilized blue phase liquid crystal system was able to increase by doping the samples with different monomers with a different functional group and chain length. The morphological study demonstrated that monomer functionality have a significant role in the formation polymer network in a different density and morphology. Furthermore, the results showed that the polymer network density has an effect on the mechanical performance of polymer stabilized BPLC sample. The polymerizable monomers lead an enhancement in the mechanical property of polymer stabilized BPLC sample. © 2018 Elsevier LtdItem A study on the mechanical and morphological behavior of polyurethane-encapsulated cholesteric liquid crystal composite films(SAGE Publications Ltd, 2020) Kemiklioglu E.; Kemiklioğlu U.; Sayman O.This study explores the preparation and mechanical behavior of free-standing polymer-dispersed liquid crystal (PDLC) film membranes. Polyurethane (PU) was used as a thermoplastic polymer matrix to form these free-standing film membranes. Cholesteryl oleyl carbonate (COC) and cholesteryl pelargonate were used as liquid crystals (LCs) with different molecular weights. PDLC membranes were produced by casting method after LCs and polymer were mixed in the tetrahydrofuran solvent at room temperature. These membranes were formed at different concentration ratios of polymer and LCs. The relationship among the phase separation, LCs and polymer contents as well as the LCs molecular weights was investigated. The morphological structures of these membranes were studied using scanning electron microscopy (SEM). SEM images exhibited that the shapes of LC droplets embedded in PU matrix were more uniform and smaller than those of the membranes which include LC with lower molecular weight. The mechanical properties of the PDLC membranes were determined by carrying out the tensile tests. It was found that the membranes which include COC LC were more flexible. © The Author(s) 2020.Item Development an optical sensor using lyotropic cholesteric liquid crystals for the detection of toxic gases(Elsevier GmbH, 2021) Kemiklioglu E.; Gurboga B.; Tuncgovde E.B.In the current study, a lyotropic cholesteric liquid crystal (ChLC) based sensor for the identification of vapors of polar (toluene and phenol) and apolar (1,2 dicholoropropane) toxic gases was investigated. The lyotropic ChLC sample including cholesteryl oleyl carbonate, cholesteryl pelargonate, and cholesteryl benzoate was supported on the chemically modified glass surfaces as an optical sensor for the detecting of these toxic gases vapors. The glass surfaces were modified by coating Dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP). The optical signal generated by the incorporation of different toxic gases vapors in the lyotropic ChLC layers which disturbs the pitch length. These toxic gases were evaporated at different temperatures and the exposure time was differentiated. Increasing solvent evaporation temperature lead a shift in the wavelength maximum to smaller wavelengths which can be observed by a naked eye. © 2021 Elsevier GmbHItem Development of liquid crystal biosensor for the detection of amyloid beta-42 levels associated with Alzheimer's disease(Elsevier B.V., 2021) Kemiklioglu E.; Tuncgovde E.B.; Ozsarlak-Sozer G.This study represents the development of a biosensor which is based on the liquid crystal (LC) orientation as a function of the peptide concentration to detect an amyloid-beta-42 (Aβ42) antibody–antigen binding events. The Aβ42 peptide binds to the Aβ42 antibody forming an immunocomplex which is immobilized on the Dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP) coated surface. The disturbed orientation of LCs as a result of the binding of the formed immunocomplex was observed using the polarized optical microscope (POM) as a function of decreasing Aβ42 peptide concentration from 1000 to 1 pg/ml. The concentration, as low as 1 pg/ml of Aβ42 peptide was able to be successfully detected in our system. Apolipoprotein E4 (ApoE4), that specifically bound to the Aβ42 peptide, was added into the system and a remarkable change in reflection spectra of samples was observed with increasing Aβ42 peptide concentration. The concentration of ApoE4 protein was detected in the range of 0.1–30 nM by this system due to the interaction between the two proteins. © 2021 The Society for Biotechnology, JapanItem Liquid crystal-based elastomers in tissue engineering(John Wiley and Sons Inc, 2022) Gurboga B.; Tuncgovde E.B.; Kemiklioglu E.Liquid crystal elastomers (LCEs) play role in tissue engineering investigations, with the combination of orientational ordering generated by liquid crystal (LC) moieties and the elastic capabilities of polymers. Liquid crystal-based polymer materials require a thorough understanding of their features that set them apart from other smart materials for proper design and application. LCEs offer many advantages for their widespread use in the field of biomaterials, by virtue of their simplicity of processing, anisotropic behavior, and responding to numerous external stimuli. Especially, LCEs have widespread usage in bioengineering applications such as scaffolds due to their biocompatibility, viability, and proliferation properties of these materials. This study introduces a brief overview of the new areas of liquid crystal-based elastomer applications combining both biomaterials and engineering. © 2022 Wiley Periodicals LLC.Item Optical sensing of organic vapor using blue phase liquid crystals(Taylor and Francis Ltd., 2022) Gurboga B.; Kemiklioglu E.This study presents the investigation of the use of blue phase liquid crystals (BPLCs) for the sensing of toxic gas vapours of toluene, phenol and 1,2 dichloropropane. The vapours of these three toxic solvents were obtained by evaporating at different temperatures within the different times, and BPLC was separately exposed to these gas vapours. The diffusion and adsorption of these vapours on the BPLCs were investigated depending on the dimensions and polarity of the molecules. The optical response of BPLC exposed to gas vapours of toluene, phenol and 1,2 dichloropropane was determined with Bragg reflection wavelength as a function of temperature and time. We found that BPLC produced a remarkable change to the red side of the spectrum due to diffusion of toluene gas vapour by the BPLC sample and itsBragg reflection wavelength change within the time showed a good linearity correlation. Moreover, the diffusion coefficient of the toluene gas vapour in BPLC sample was calculated, and it was determined as 8.224 × 10−12 (cm2/s) by using a least-squares method. © 2022 Informa UK Limited, trading as Taylor & Francis Group.Item Modeling of the lyotropic cholesteric liquid crystal based toxic gas sensor using adaptive neuro-fuzzy inference systems(Elsevier Ltd, 2024) Araz O.U.; Kemiklioglu E.; Gurboga B.Detection of toxic gases is important in a variety of settings, including industrial facilities, laboratories, and even in homes. In these settings, toxic gas detection can help prevent accidents and protect the health and safety of workers, researchers, and others who may be exposed to these gases. This study evaluates an Adaptive Neuro-Fuzzy Inference System (ANFIS) models in predicting the machining responses in the detection of toxic gases vapor, such as toluene (T), phenol (P) and 1,2 dichloropropane (D) using lyotropic cholesteric crystal (CLC) have been shown to have potential as gas sensors due to their unique optical and liquid crystal (LC) properties, and the ANFIS model may be used to better understand and optimize these properties for toxic gas detection. Experiments were carefully carried out to gather data on the response of a lyotropic CLC toxic gas vapor sensor. The effectiveness of using ANFIS combined with Grid Partitioning (GP) was then carefully studied and evaluated in terms of modeling and predicting the responses of the sensor. The best ANFIS-GP model is chosen from these criteria; RSS, PCC, R2, RMSE, MSE, MAE, and MAPE. In addition, validation was performed between the model and experimental data using the LOOCV method. The results show that the ANFIS-GP5 model with 96 fuzzy inference systems (FIS) rules with high R2 values. According to the ANFIS-GP5 model, R2varied ranges from 0.77 to 1 for train, test, and total data of lyotropic CLC sensor exposed to toluene, phenol and 1,2 dichloropropane toxic gases vapors. © 2023 Elsevier LtdItem Biological and mechanical evaluation of cinnamaldehyde doped liquid crystal-polymer composite membranes(Taylor and Francis Ltd., 2024) Seylan Akış M.; Kemiklioglu E.; Kemiklioğlu U.In this study cinnamaldehyde (CA) doped polyurethane cholesteryl pelargonate cholesteric liquid crystal composite membranes were produced and their properties were examined for use in biological applications. The relationship between the blood coagulation and protein adsorption was studied and the results showed that increasing CA concentration allowed an improvement in biological properties of them. Additionally, the effect of CA on the hyrophobicity of these membranes was investigated by determining water holding capacity, contact angles. The mechanical strength of these membranes were determined and it was found that their strength increased and the ability to elongate decreased with an increasing CA dopant concentration. © 2023 Taylor & Francis Group, LLC.