Photon Correlation Spectroscopy of Polymer Latices

Abstract

Polymer latices are frequently used as calibration standards in photon correlation spectroscopy (P.C.S.) and as beginners in this field, we chose to work with them in order to gain experience and understanding of the technique. Our apparatus at RMCS currently consists of a 25 mW He-Ne laser (Scientifica and Cook; Model B30), a Malvern Instruments Type 4300 spectrometer and Digital Correlator (K 6023) with 72 memory channels and a Hewlett Packard Programmable Calculator (Model 9821 A) with associated X-Y plotter. Sample preparation was carried out in a clean room at RMCS using doubly distilled filtered water. All samples were filtered using millipore filters of appropriate sizes. The normalisation and data analysis followed the procedure given by Pusey and S_m was routinely fitted to both first and second order polynomials in τ. In all results the quality parameter Q was no more than a few percent and frequently smaller, being less than the experimental error in the square law coefficient. The first order coefficient gave us an effective linewidth Γ_eff which relates to the effective particle diameter d_eff via the Stokes-Einstein relation

$$\Gamma _{eff} = \frac{{kT}}{{3\pi \eta \,d_{eff} }}$$