DETERMINATION OF SCALING PROPERTIES OF RANDOMLY BRANCHED POLYCYANURATES BY COMBINED SEC/LALLS/VISC

Size exclusion chromatography coupled with refractive index, light scattering, and viscosity detectors and viscometry are employed to study the scaling behavior of trifunctional randomly branched polycyanurates. An exponent tau=2.22+/-0.02, which is close to the prediction of three-dimensional percolation theory, was found for the molecular weight distribution w(M) is similar to M(l-tau) f(M/M*), where f(M/M*) is a cutoff function and M* is the cutoff molecular weight. The exponent a = 0.34 +/- 0.02 in the relationship [eta] is similar to M(a) for fractionated polymers gives a fractal dimension D = 2.24 +/- 0.03 which agrees well with D = 2.21 +/- 0.04 derived from b = 0.20 +/- 0.03 in [[eta]] is similar to M(w)b for unfractionated polymers according to a theory of Daoud, Family, and Jannink. Both values remain within the theoretically predicted limits of D = 2.5 for the unswollen state and D = 2.0 for the fully swollen state. These findings lead to the conclusion that the polycyanurates with their complex chemical structure when synthesized in bulk can swell only slightly in the good solvent THF. Furthermore, the exponent c = 0.66 +/- 0.05 in the relationship A2 is similar to M(w)-c for the second virial coefficient was found to satisfy the relationship a + c = 1. The resulting constant value of MA2/[eta] = 2.14 +/- 0.06 for the randomly branched polycyanurates is higher than the value of 1.1 for linear chains, which implies a constant ratio PSI(b)/PHI(b) for fractionated polymers, whereas the molecular weight dependence PSI(b)/PHI(b) is similar to M(w)0.14 found for unfractionated polymers is caused by the differently weighted averages of M, A2, and [eta]. The physical meaning of the ratio PSI(b)/PHI(b) is discussed.