(181bj) Molecular Architecture Vs Reaction Conditions: Comprehensive Modeling of Arget-ATRP of Styrene-Acrylonitrile Copolymerization

Activators ReGenerated by Electron Transfer – Atom Transfer Radical Polymerization (ARGET-ATRP) has enormous potential for producing all kind of specialty polymers with controlled molecular properties.^[1] This polymerization technique has proved to be suitable to co/polymerize a large number of different monomers with targeted molecular weights, composition or architecture in a simple way, feasible to implement in large scale.^[2]

End-use properties are dependent on molecular structure of polymer.^[3] Therefore, the ability to manipulate the chain architecture is crucial to produce materials with an outstanding performance. Comprehensive modeling eases this task by providing straightforward relationships between structure and reaction conditions, helping the experimentalist to find suitable recipes reducing costly trial and error experiments.^[4] Moreover, the simulation of polymerization can help find the variables that impact the most on polymer properties and optimize the production in terms of conversion and reaction time.^[5]

In previous works we have developed an efficient and comprehensive mathematical model able to predict the average and distributed molecular properties of copolymers synthetized by ARGET-ATRP. The average properties are predicted using the well-known method of moments while the molecular weight distribution (MWD) and the 2D molecular weight distribution-copolymer composition distribution (MWD-CCD) are modeled using the probability generating function (pgf) technique.^[6]

In this work we have adapted this model to the ARGET-ATRP copolymerization of styrene and acrylonitrile to estimate the kinetic rate constants that remain unknown for this polymerization mechanism. Additionally, the model provides detailed information on the course of the reaction and the molecular structure that cannot be obtained directly from experimental techniques.

In particular, the kinetic rate constants of the ATRP equilibrium and the reduction steps for the ARGET-ATRP of S and AN were estimated from the experimental data reported by Pietrasik et al.^[7] with accuracy. The system under study was the copolymerization of styrene (S) and acrylonitrile (AN) in solution (anisole as solvent) using ethyl α-bromoisobutyrate (EBiB = I) as initiator, CuCl2 (CuII) complexed with hexamethyl-tris(2-aminoethyl)amine (Me6TREN = L) as the deactivator, and tin(II) 2-ethylhexanoate (Sn(EH)2 = SnII) as reducing agent. The kinetic mechanism is based in the one proposed by Al-Harthi et al. for the conventional ATRP copolymerization of styrene and acrylonitrile.^[8]

• References

[1] K. Matyjaszewski, Advanced Materials 2018, 30,

[2] W. Jakubowski, B. Kirci-Denizli, R. R. Gil, K. Matyjaszewski, Macromolecular Chemistry and Physics 2008, 209, 32.

[3] N. Badi, D. Chan-Seng, J. F. Lutz, Macromolecular Chemistry and Physics 2013, 214, 135.

[4] WO 2011/075156 Al - "Improved Control over Controlled Radical Polymerization Processes", 2010.

[5] E. Mastan, X. Li, S. Zhu, Progress in Polymer Science 2015, 45, 71.

[6] C. Fortunatti, E. Pintos, C. Sarmoria, A. Brandolin, M. Asteasuain, in XVI Latin-American Polymer Symposium (SLAP 2018).

[7] J. Pietrasik, H. Dong, K. Matyjaszewski, Macromolecules 2006, 39, 6384.

[8] M. Al-Harthi, J. B. P. Soares, L. C. Simon, Macromol. React. Eng. 2007, 1, 468.