Bivariate distribution in copolymers: A new model

A new model for the bivariate distribution of chain sizes and composition in copolymers is presented. The model combines the sum of a two‐bivariate distribution, and it replaces the previous model that consists of a single entity. The compositional distribution histogram was obtained by summation of the sections of the bivariate distribution that belong to a narrow compositional range. The predictions of the model were compared with mass spectrometric data relative to a block copolymer sample containing structural units of pivalolactone and 3‐hydroxybutyrate with some literature data, namely, mass spectrometric data concerning a random copolymer sample reacted at high conversion containing units of styrene and methyl methacrylate as well as a block copolymer sample containing units of α‐methyl styrene and methyl methacrylate. The new model gives better results than the previous model because it fits better with the experimental compositional distribution histogram of the copolymer samples. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2442–2448, 2002