STATE OF GELATION OF FULLY CONJUGATED CONDUCTING GELS - GEL FRACTION,SWELLING, AND NUCLEAR MAGNETIC-RELAXATION

Statistical properties of well-defined fully conjugated poly(3-octylth iophene) (POT) gels are explored above glass transition and fusion tem peratures by varying the cross-link functionality, f, and the cross-li nk concentration, R-i. Four series of gels are prepared using four dif ferent cross-linking agents. The state of gel connectivity, characteri zed by the gel fraction is found to depend on the distance to the gela tion threshold, epsilon, expressed within a mean-field percolation app roach. In the range of explored crosslink densities, H-1 NMR and swell ing experiments reveal that the active structural strands of both dry and swollen gels are the linear chain segments defined by adjacent cro ss-links. These segments are disengaged from one another in swollen ge ls. The two variables, chain segment contour length and epsilon, are f unctions of the product fR(i). This parameter is the relevant variable for the description of POT gel structures: master curves of the quant ities gel fraction, swelling ratio, and H-1 transverse relaxation rate are obtained versus fR(i).