Shear light scattering photometer with optical microscope for the study of polymer blends

Abstract

A shear light scattering photometer with an optical microscope was constructed for the study of polymer blends in a simple shear field. This instrument utilizes a cone and plate or parallel plate geometry for the generation of shear field. The shear rates are controlled by a microstepping motor. The controllable range of shear rate is between 0.002 and 1000 s−1. The bottom plate of the shear cell has a special design to accommodate the microscope objective and a thin disk-type heater for temperature control. The accessible q range is from 0.7 to 4.6 μm−1 with a 632.8 nm He–Ne laser or from 0.9 to 6.0 μm−1 with a 488 nm Ar ion laser. The temperature can be controlled from ambient temperature to 250 °C with ±0.1 °C accuracy. A phase contrast microscope and a fluorescence microscope are built into this photometer for the in situ morphological study of materials of interest. The optics for light scattering and microscopy can be switched back and forth by a simple translational movement of a rail-mounted optical platform, without any realignment, for comparison of data from reciprocal space with that from real space. A bulk polystyrene/polybutadiene blend and a polystyrene/polybutadiene/dioctylphthalate blend were used to demonstrate the performance and versatility of this instrument.

Ubiquity of domain patterns in sheared viscoelastic fluids

“…The in situ scattering/microscopy instrument is described in detail elsewhere [8]. The flow is along the x axis, with a constant velocity gradient along the y axis and vorticity along the z axis [ Fig.…”

Shear-induced structure in polymer–clay nanocomposite solutions

“…The shear light-scattering photometer with optical light microscope was constructed at the National Institute of Standards and Technology [18]. The instrument provides realand reciprocal-space measurements under steady shear over length-scales greater than 1 µm in the x-z (flow-vorticity) plane.…”

String Formation in Sheared Polymer Blends: Coalescence, Breakup, and Finite Size Effects

“…In this work, we investigate the limit where a 0 becomes comparable to and smaller than the gap thickness d. Since s ᠨ gh, where ᠨ g is the matrix shear rate and h is the matrix viscosity, we can experimentally vary a 0 through its dependence on ᠨ g. The shear-induced structures are generated by placing the sample in between two parallel quartz disks and rotating the upper one at a controlled rate. The shear rate is then ᠨ g n͑r͒͞d where n͑r͒ is the upper plate velocity at the radial point of measurement r. Stroboscopic optical microscopy is utilized to visualize the structures, and the data are recorded onto videotape for subsequent analysis [15]. The minority component is Polydimethylsiloxane (PDMS), used at a mass ratio of 0.28 which is within the range typically utilized in industrial polymer processing, and the majority component is Polyisobutylene (PIB).…”