NUMERICAL STUDY OF SCATTERING FROM CHAINS COMPOSED OF 2 NONSEGREGATEDLABELED BLOCKS IN AN ATHERMAL SOLVENT - EFFECTS OF COMPOSITIONAL HETEROGENEITY

Numerical calculations and Monte Carlo simulations have been performed to explore the dynamic scattering behavior of solutions of copolymer chains composed by two nonsegregated blocks in an athermal solvent. Th e experimental investigation of this property for real copolymers has shown the presence of a variety of modes, with a complex variation of their locations and intensities, which we try to partially understand with the present simulation work. For this purpose, we use chain sampl es with a small amount of polydispersity in the block lengths. We have introduced opposite scattering contrast factors for the A and B units . In this way, zero-averaged contrast conditions have been set for the overall scattering, avoiding the presence of the collective mode that otherwise would manifest for any nondilute system of polymer chains. Static and dynamic scattering functions have been obtained for the dif ferent samples. For the dynamic scattering functions, three modes are observed in agreement with existing experiments. The first two modes, predominant for low values of the scattering variable, q, are assigned to correspond to the compositional heterogeneity and the first intern al relaxation of the chains, as predicted by the theory. The variation of the mode intensities and positions with polymer concentration is a nalyzed. It semiquantitatively agrees with the existing experimental d ata. (C) 1998 American Institute of Physics.