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 -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.