THE CONFORMATION OF LINEAR AND STAR POLYMERS IN THE IDEAL STATE

We briefly review some recent experimental results on the ideal state of linear and star polymers. This state is achieved in a melt and in s olution at the Theta temperature. From the theoretical study of the in ter- and intra-molecular interactions, we suggest that in a melt the l ong-range intramolecular interactions vanish because of the screening exerted by the surrounding chains. The chain conformation is then very close to a random walk for any polymer architecture. Conversely, in s olution, at the Theta temperature, these interactions do achieve compl ete compensation only in linear chains, while they survive to some ext ent in star polymers, leading to an observable finite expansion. The m olecular basis of this effect is also discussed.