Particle scattering form factors of chemical and conformational triblock copolymers

Partially substituted derivatives of cellulose display unusual behavior. Aggregates are found which resemble star-branched macromolecules. The dimensions of these aggregates are large and indicate either an uncommon chain stiffness of the arms, or a structure that consists of two star-branched coronas which are connected over a rigid stem composed of f-laterally aggregated cellulose chains. This structure may be considered as the smallest object in the fringed micellar crystal structure of native cellulose and is given the name fringed micelle. Ln the present paper the angular dependence of the scattering intensity in visible light (LS) and small angle neutron scattering (SANS) of such conformational tri-block copolymers is derived. The theory is based on the mean field approach. Closed expressions are obtained by application of Gordon's cascade theory. The theory can describe the scattering curves in the whole q = (4 pi/lambda)sin(theta/2) range of LS and SANS. The derived solutions have to be considered as a first approximation since the effect of excluded volume has not been taken into account. Attempts are in progress to find a suitable approximation for this problem. (C) 2000 Elsevier Science Ltd. All rights reserved.