''Butterfly''-like patterns of triblock copolymer gels as observed by small-angle neutron scattering

At high (150-1000%) stretching of a physical gel of a triblock copolymer a ''butterfly''-type scattering pattern is observed with a pronounced scattering-free strip perpendicular to the stretching direction. The phenomenon is attributed to the cluster character of the physical network in the gel. Stretching brings endblock domains (junction points of the network) closer to each other in the direction perpendicular to the stretching and leads to formation of a layered structure. High connectivity of the network inside the clusters leads to saturation of the deformation within the clusters as manifested by the scattering-free region in the SANS pattern. (C) 1996 John Wiley & Sons, Inc.