Large amplitude oscillatory shear (LAOS) and the Laponite gels
Among the methods of nonlinear rheological measrument, large amplitude oscillatory shear (LAOS) is unique because it separately controls the time scale (in frequency) and the deformation scale (in strain amplitude). The input of a sinusoidal and the harmonic analysis of the output fit into the context of other nonlinear system research (e.g. nonlinear susceptibility). A review on LAOS is available here. I also wrote a small account of its history.
The structure of Laponite gel
In my research, LAOS is used to investigate the rheological behavior of Laponite gel. Laponite is a synthetic hectorite. It disperse in water into nano-sized platelets, but undergoes gelation over time. The gels formed is thixotropic, which mean it melts under large deformation, and takes time to recover after the deformation ceases or lowered to an extent. Moreover, the gelation or recovery process is sensitive to external deformation. These rheological behaviors are not only nonlinear viscoelastic, but also time-dependent. Therefore the current LAOS methods have to be extended to time-dependent situation.
My work thus involves the development of the time-resolved LAOS technique, and the subsequent investigation of the gelation process of Laponite gels, under small or large strain amplitude. I also investigate the effect of adsorbed polymer (PEG) on the particle surface on the gelation process. See my publication list.
Rheometric expriences
During my study I gain some experiences in dealing with the ARES-RFS rheometer and setting up a new measurement system. I would like to share in the following pages:
- Replacing the peltier plate
- Noises of ARES-RFS (unfinished)
- More is coming …
Earlier works and experiences
Click here to know my experiences during undergraduate years (Sep. 2001-Jun. 2005).
Crystallization induced ordering
I complete the Master degree during Sep. 2005 ~ Jun. 2008, during which I synthesized block copolymers contining polyethylene glycol (PEG) and polylactic acid (PLA) blocks, investigated their crystallization and micelles, and the inclusion complex formation with α-cyclodextrin. Click here for details.
