A Time-Resolved Low-Angle Light Scattering Apparatus. Application to Phase Separation Problems in Polymer Systems

Abstract

A time-resolved small-angle light scattering apparatus equipped with azimuthal integration by means of a conical lens or software analysis of scattering patterns detected with a CCD camera was developed. Averaging allows a significant reduction of the signal-to-noise ratio of scattered light and makes this technique suitable for investigation of phase separation kinetics. Examples of applications to time evolution of phase separation in concentrated statistical copolymer solutions and dissolution of phase-separated domains in polymer blends are given.

Determination of Size Distributions of Concentrated Polymer Particles Embedded in a Solid Polymer Matrix

“…particle size, particle concentration, and to some extent, particle-matrix optical contrast. It has been reported in the literature [19] that systems of immobile particles like the ones analyzed here may display an important level of speckle effect when scattered light is measured with linear arrays of diodes. Speckle effect may negatively impact on the quality of the measured LS spectra.…”

Particle Systems Characterization Using a Flat Cell Static Light Scattering Apparatus

“…Linear arrays of diodes used to sense light scattered by systems of particles have several advantages in terms of resolution, calibration, and data manipulation, as compared to other alternatives. However, it is recognized that, due to the speckle effect, they may not be the best choice for use to detect scattered light from inhomogeneities that have little mobility, such as those considered in this work [11]. In this study, it has been shown that a proper combination of beam expansion and sample thickness may help to reduce the speckle effect to a level which becomes irrelevant, and maintains only the beneficial features of linear arrays in this form.…”

“…A single motion detector apparatus equipped with azimuthal integration by virtue of a conical lens has also been proposed to achieve time resolution. Although the time required to collect all the angles is larger than in the systems mentioned above, it is still short enough to follow the evolution of many practical systems of interest [11]. The different configurations described above fall under the so-called Small Angle Laser Scattering (SALS) apparatus (h < 40°), and have been used to study systems of particles with sizes larger than 1 lm.…”