Ordering Phenomena in ABA Triblock Copolymer Gels

Temperature and concentration dependencies of the degree of order in ABA triblock copolymer gels are discussed. Two factors can influence the ordering phenomena: the conformation of the midblocks (links of the network) and the polydispersity of the endblock domains (nodes of the network). The latter is defined by the scattering density profile (polymer chain packing) at the domain boundary: a sharp boundary corresponds to less polydisperse domains and to increased order in the arrangement of the network nodes. The structure of the network can be described in terms of a highly distorted crystalline lattice with close-packed spheres or with cubic (presumably BCC) equilibrium morphology. The appearance of the latter is never detected in the gels with a stretched conformation of the midblock.