Recommendation for Accurate Experimental Determination of Reactivity Ratios in Chain Copolymerization

• Published in: Macromolecules Vol. 52; no. 6; pp. 2277 - 2285
• Main Authors: Lynd, Nathaniel A, Ferrier, Robert C, Beckingham, Bryan S
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26-03-2019
• DOI: 10.1021/acs.macromol.8b01752
• EISSN: 1520-5835
• ISSN: 0024-9297

A set of copolymerization data at prescribed reactivity ratios was numerically generated and then fit using common methods of data analysis including the copolymer equation, Fineman–Ross, Kelen–Tüdös, and integrated methods of data analysis, such as those reported by Beckingham, Sanoja, and Lynd, and Meyer and Lowry. Significantly, the nonintegrated approaches based on the copolymer equation returned systemically inaccurate reactivity ratios, whereas the integrated methods produced consistently accurate reactivity ratios across 560 calculated data sets. Hence, to determine reactivity ratios with the greatest accuracy and efficiency, we recommend that copolymerization data be fit simultaneously to the models reported by Beckingham–Sanoja–Lynd (BSL) and Meyer–Lowry (ML). If the reactivity ratios are consistent, then a nonterminal model of copolymerization adequately describes the copolymerization with a single reactivity ratio parameter. If there is a difference in the reactivity ratios between BSL and ML, then the ML-derived values take precedence and a terminal model of copolymerization describes the kinetics of the system with two independent reactivity ratios. This prescription will ensure that the model with the least complexity will be used to interpret data, and that the reactivity ratios reported are most accurate and descriptive of the underlying copolymerization mechanism. Future use of the copolymer equation, Fineman–Ross, and Kelen–Tüdös to interpret copolymerization data is strongly discouraged due to unquantifiable inaccuracy and needlessly wasted experimental effort.