Randomly Branched Polymers: Semidilute Solutions

We study the conformation of randomly branched polydisperse polymers in semidilute solutions. Starting from the dilute case, when the different macromolecules are far apart from each other, we suggest that above a concentration C*, where the polymers come into contact, a semidilute regime occurs. In this regime, one may separate the distribution of molecular weights into two parts. The smaller molecules behave as in the dilute regime. They penetrate the larger ones and screen out the excluded-volume interaction. Thus large polymers behave as in the reaction bath. As a function of the weight-average molecular weight Mw, we find that the crossover concentration C* separating the dilute and semidilute regimes is C* ~ Nw-3/8. In the semidilute range, we find Rz~ Nw1/2C-1/3where C is the total monomer concentration and a screening length ξ ~-5/3We also discuss the scattered intensities in small-angle neutron and light scattering experiments in different conditions and the osmotic pressure as a function of concentration. © 1988, American Chemical Society. All rights reserved.