Methods and Systems for Monitoring and Controlling Surfactant Concentration in Liquid Crystal Colloidal Dispersions
Abstract: Nanoparticle dispersions are becoming increasingly important in many applications. However, the reproducibility and stability remain a challenge. One major parameter related to these problems is the surfactant concentration and distribution. It is important to optimize the surfactant amount which is just enough to cover the particles of ideal size. Less than enough surfactant leads to aggregation and poor stability of the dispersion, while excess surfactant might act as impurities and significantly change the properties of the host material, such as liquid crystals. In this new technology we proposed FTIR spectroscopic techniques to evaluate the surfactant distribution and concentration. Using these techniques, we studied a ball milled process for producing ferro- electric nanoparticles. We were able to measure the portion of surfactant molecules bond to the particle surface and that freely suspended in the medium. For a designated grinding time (related to particle size), we can pinpoint the ideal surfactant concentration that is needed to just cover the particle surfaces. We also developed method to evaluate the influence of freely-suspended surfactant to a liquid crystal host. Therefore, in a dispersion containing surfactant covered particles and excess surfactant molecules, we can extract and optimize the actual particles' effect without physically removing the excess surfactant molecules. These techniques are important and effective in the process of developing and optimizing reproducible nanoparticle dispersions.
Applications: Tocontrol the surfactant level in particle dispersions in general
- Highly useful
Inventors:Dr. Ke Zhang, Hari M. Atkuri, Dr. John L. West
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