DYNAMIC SCATTERING FROM CYCLIC DIBLOCK-COPOLYMER CHAINS IN SOLUTION

This paper discusses the dynamic-scattering properties of an (A-B)r ring diblock-copolymer chain in semi-dilute solutions. The expressions of the frequencies describing the dynamic behaviour of such systems are given in both models: the Zimm model, where the hydrodynamic effects are important and the Rouse model, where these effects are neglected. The results show sensitive differences with respect to the corresponding linear diblock copolymer (A-B)l. This is mainly due to the effect of connectivity of the chain extremities A and B, leading to different conformations for both types of diblock-copolymer chains. Although the description we discuss in this paper is valid for any cyclic diblock-copolymer chain (i.e. at any composition), explicit equations are given for the symmetrical case (50/50 composition) where the effects are more pronounced. Experimental investigations using neutron spin echo (NSE) are particularly useful in order to test these theoretical predictions.