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.