Dresden 2014 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 41: Poster - Pattern/ Nonlinear Dyn./ Fluids/ Granular/ Critical Phen.

DY 41.5: Poster

Donnerstag, 3. April 2014, 17:00–19:00, P3

Optical birefringence in dried laponite films — •Pawan Nandakishore, Anupam Sengupta, and Lucas Goehring — Max Planck Institute for Dynamics and Self-Organization (MPIDS)

The emergence of anisotropy in a material can be attributed to either the structure of the materials or the buildup of internal stresses within a material. Using Optical polarization microscopy we study dried laponite suspensions under ambient conditions. We observe birefringence in the bulk and on the edges of dried laponite films. Laponite is know to transition from an isotropic liquid to an isotropic gel and finally to a nematic gel as a function of the initial concentration and changing salinity. We observe that dried samples of laponite are birefringent even when the laponite concentration before drying is in the isotropic gel phase regime. The birefringence scales with concentration before drying and reaches a maximum when it is in the nematic phase regime. Bulk birefringence in the dried samples can be attributed to ordering of laponite disks due to drying where as the birefringence in the edge is stress induced. We observe similar stress induced birefringence at edges of a crack opening and along the edge of laponite thick films (millimeter-centimeters films). Dried laponite films are model systems to study stress induced birefringence and birefringence due to structural anisotropy.