POLYAMPHOLYTES - FROM SINGLE CHAINS TO SOLUTIONS

We discuss multichain effects in salt-free polyampholyte solutions of finite concentration and find that the existing single-chain theories are limited to exponentially small concentrations, if the sample conta ins chains with net charges of both signs. We show that charged polyam pholytes have a strong tendency to form neutral complexes and to preci pitate. Neutral samples, where the average net charge of the chains is exactly zero, phase separate at exponentially small concentrations. T he supernatant is dominated by neutral unimers or clusters that form s pherical globules and its polymer concentration c(dil) similar to exp( -(N) over tilde(2/3)) is independent of the total polymer concentratio n. For non-neutral samples, on the other hand, the free counterions ac cumulate in the supernatant together with the most strongly oppositely charged unimers, if the system is concentrated beyond the onset of ph ase separation. The dilute phase then consists of elongated globules a nd has a concentration proportional to the total polymer concentration .