Electric birefringence of polytetrafluoroethylene particles in agarose gels

Electric birefringence studies of strongly elongated, rod-like particles of polytetrafluoroethylene (PTFE) in agarose gels show that the negative effect observed by semi-diluted aqueous suspensions at low frequencies and at low electric field strengths (the so called "anomaly') disappears. The absolute value of the low frequency effect increases 3-4 times and the amplitude of modulation decreases faster compared to that of the suspensions. This together with decreased decay relaxation times in gels make the possibilty that the PTFE particles orientation in gels is not due to dipolar but to electrophoretic orientation mechanism quite probable. Similar change in the orientation mechanism could be expected also for suspensions of higher concentrations. The further elucidation of the orientation mechanism using fractions with lower polydispersity, broader ranges of experimental conditions (particle concentration, ionic strength and composition, electric field strengths, frequencies, etc.) could be interest for several fields: colloid electro-optics and especially that of concentrated colloids, pulsed field gel electrophoresis of DNA (and especially its sinusoidal biased field variant) and of nucleoprotein complexes and for the gel research.