Calculation of Molecular Weight Distributions in Non-Linear Free-Radical Polymerization Using the Numerical Fractionation Technique

• Published in: Macromolecular theory and simulations Vol. 11; no. 5; pp. 533 - 548
• Main Authors: Papavasiliou, Georgia, Birol, İnanç, Teymour, Fouad
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag GmbH 01.06.2002; WILEY‐VCH Verlag GmbH; Wiley
• Subjects: Applied sciences; Deterioration; Exact sciences and technology; Fractionation; gelation; Mathematical models; Method of moments; modeling; Molecular weight distribution; molecular weight distribution/molar mass distribution; Nonlinearity; Organic polymers; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; radical polymerization; Shoulders; Branching; Kinetic model; Free radical polymerization; Chain transfer; Molecular weight distribution; Non linear process; Gelation; Moment method; Theoretical study; Computing method
• ISSN: 1022-1344; 1521-3919
• DOI: 10.1002/1521-3919(20020601)11:5<533::AID-MATS533>3.0.CO;2-O

Mathematical Modeling of non‐linear polymerization systems subject to gel formation is a challenging endeavor. At the gel point, the second and higher molecular weight moments diverge to infinity making it impossible to obtain the molecular weight distribution (MWD). The numerical fractionation (NF) technique utilizes a refinement of the method of moments to model non‐linear polymerization systems that form gel. Since the method of moments yields results in terms of average quantities, some information is lost when reconstructing the MWD using NF. As a consequence, a broad shoulder appears at the high chain length end of the MWD tail. This study demonstrates that the validity of the gamma distribution deteriorates for the broader branched polymer generations and evaluates the performance of various alternative model distributions. Proper selection of the model distribution enhances the NF‐reconstructed MWD.