Controlled synthesis of organic-inorganic composite particles

Erçelik, Elif
Liquid crystal (LC) is a state of matter having long-range orientational order between crystalline solid and isotropic liquid, and its molecular orientation can be altered with external stimuli. The polymerization of liquid crystal droplets has been widely used for the synthesis of LC-templated functional materials due to its ordering property and fluidic behavior. In this study, we investigated the synthesis of composite particles with controlled internal and interfacial structure using surface-modified nanoparticles-adsorbed LC droplets as templates. In the first part of this study, we synthesized silica nanoparticles, silver nanoparticles, and iron oxide nanoparticles and modified their surfaces by using thiol or silane groups to procure either planar, tilted, or homeotropic anchoring to LC droplets and pH-dependent surface charge, hydrophobicity, and hydrophilicity. Secondly, we adsorbed nanoparticles to the LC-aqueous interface and characterized the configurations (internal structuring) of LC droplets. We showed that surface chemistry, concentration, and surface charging of nanoparticles affect the change in configuration of LC droplets and form heterogeneity on the surface. According to our results, adsorption of silver and iron oxide nanoparticles modified with 1-decanethiol and 1-hexadecanethiol (-C10/C16 mixed monolayers of thiols) showed a transition from bipolar to radial, whereas -COOH/C16 mixed monolayers of thiol terminated nanoparticles (tilted) changed the configuration to preradial. Adsorption of silica nanoparticles modified with dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP, homeotropic) and -COOH/DMOAP terminated counterparts exhibited a configuration change from bipolar to radial and preradial, respectively. -NH2 and -COOH terminated counterparts (planar) did not change the configuration. Thirdly, we used -NH2 and -COOH terminated silica nanoparticles with different sizes (51.2 nm ± 9.0 nm to 417.1 nm ± 22.1 nm), tuned their surface charges by changing pH, and finally polymerized the LC droplets after adsorption. Charging property of -NH2 and -COOH terminated silica nanoparticles provided adsorption control. We showed partial coverage of charged, surface-modified silica nanoparticles to enable their preferential positioning, which offered control over the interfacial structure for composite particles. These results in this study provide a basis for synthesizing anisotropic, polymeric composite particles with complex structures for technological products, biomedical or sensing applications.


Design of functional materials using liquid crystals as molecular templates
Karausta, Aslı; Büküşoğlu, Emre; Kalıpçılar, Halil; Department of Chemical Engineering (2018)
Liquid crystal (LC) is a phase of material which is intermediate to a crystalline solid and an isotropic liquid such that the molecules flow but retain a degree of long-range orientational ordering. LCs, due to their long range orientational ordering and fluidic properties, can be used in templated synthesis of polymeric materials as well as self assembly of the microparticles incorporated into the LCs. In the first part of this thesis, we sought to provide control over alignment of the polymer chains, alig...
Shape Effects on the Structure and Response of the Polymeric Particles Synthesized from Cholesteric Liquid Crystal Templates
Avşar, Deniz Işınsu; Büküşoğlu, Emre (2021-01-01)
: Liquid crystals (LCs) have been shown to provide molecular templates for the synthesis of polymeric particles. Past studies have revealed the elastic effects to dominate internal configuration of the LC molecular templates for the sizes below 10 µm. Sacrificial microwells were used in this study to study the effect of shapes of the particles synthesized from the cholesteric liquid crystals on their structure and response. Specifically, mixtures of diacrylate based reactive (RM257) and nonreactive mesogens...
Liquid crystal-templated synthesis of polymeric microparticles with complex nanostructures
Akdeniz, Burak; Büküşoğlu, Emre; Department of Chemical Engineering (2019)
Liquid crystals (LC), when combined with photolithography, enable synthesis of microparticles with two- and three-dimensional shapes and internal complexities. We prepared films of nematic LCs using mixtures of reactive (RM257) and non-reactive mesogens (E7) with controlled alignment of LCs at the confining surfaces, photopolymerized the RM257 using a photomask, and then extracted the unreacted mesogens to yield polymeric microparticles. The extraction resulted in a controlled anisotropic shrinkage with an ...
Experimental characterizations of the response of nematic liquid crystal droplets upon adsorption of nanoparticles from aqueous media
Şengül, Selin; Büküşoğlu, Emre; Aydoğan, Nihal; Department of Chemical Engineering (2021-9-08)
Nematic liquid crystal (LC) droplets have been widely used for the detection of molecular species. In this study, we investigated the response of micrometer sized nematic LC droplets against the adsorption of nanoparticles from aqueous media. In the first part of this study, we synthesized ~100 nm-in-diameter silica nanoparticles and modified their surfaces to mediate either planar or homeotropic LC anchoring and a pH-dependent charge. Secondly, we carried out the adsorption of nanoparticles to the LC-aqueo...
Güler, Murat (1994-06-01)
The flow behaviour and the molecular orientation of many anisotropic fluids, like nematic liquid crystals, can be described by the Ericksen-Leslie equations. A mapping from the physical domain to a computational domain is needed for the finite-difference solution of the equations. The numerical solution of the equations of motion using an implicit scheme, which is required for stability reasons in the evaluation of the linear momentum equations, is not straightforward due to the complexity of the divergence...
Citation Formats
E. Erçelik, “Controlled synthesis of organic-inorganic composite particles,” M.S. - Master of Science, Middle East Technical University, 2022.