ELECTRIC BIREFRINGENCE OF POLYTETRAFLUOROETHYLENE PARTICLES IN AGAROSE GELS

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