(253bk) Simulation-Based Design of Copolymer Sequence Using the Kinetic Monte Carlo Method

Free radical polymerization has a wide range of applications and continues to attract research interest as the demand for tailored specialty polymers grows. Sequence distribution, tacticity and composition of copolymers play a key role in understanding the reaction kinetics and the properties of the polymers [1]. One of the chief challenges in unraveling the relationship between sequence and properties is that experimental techniques allow only some aspects of sequence to be uncovered, but do not yet measure explicit sequence distributions. Extensive research effort is being put into modeling and simulation of free radical polymerization (FRP), in order to complement experimental efforts by revealing the full sequence information of all polymer chains. Among multiple modeling techniques, kinetic Monte Carlo (KMC) has been intensively exploited for simulating polymeric reactions, because of its capability of recording the explicit sequence of every polymer chain, enabling more detailed analysis of polymer properties [2, 3]. Nevertheless, compared to deterministic models, KMC is computationally much more expensive, limiting its applications for efficient design of sequence properties.

We developed a general KMC simulation framework that simulates free radical copolymerization, with the ability to keep track of the explicit sequence of polymer formed at any instant of the reaction, from which the statistics related to sequence distribution can be easily extracted, such as dyad or triad fractions and sequence length distribution [4]. The efficiency of this simulation model is maximized, reducing the simulation time while keeping accurate results for polymer sequence distributions and other properties including molecular weight distribution and copolymer composition [5]. The model was used for simulation based design for specific targets on sequence characteristics, and has the potential of being integrated into a simulation based optimization algorithm that searches for the required synthesis conditions for desired sequence properties.

[1] M. Al-Harthi, M. J. Khan, S. H. Abbasi, and J. B. P. Soares, "Gradient Copolymers by ATRP in Semibatch Reactors: Dynamic Monte Carlo Simulation," Macromolecular Reaction Engineering, vol. 3, pp. 148-159, 2009.

[2] Y. Mohammadi, M. Najafi, and V. Haddadi�Asl, "Comprehensive Study of Free Radical Copolymerization Using a Monte Carlo Simulation Method, 1," Macromolecular theory and simulations, vol. 14, pp. 325-336, 2005.

[3] P. H. M. Van Steenberge, D. R. Dâ??hooge, M. F. Reyniers, and G. B. Marin, "Improved Kinetic Monte Carlo Simulation of Chemical Composition-Chain Length Distributions in Polymerization Processes," Chemical Engineering Science, vol. 110, pp. 185-199, 2014.

[4] V. R. Regatte, H. Gao, I. A. Konstantinov, S. G. Arturo, and L. J. Broadbelt, "Design of Copolymers Based on Sequence Distribution for a Targeted Molecular Weight and Conversion," Macromolecular Theory and Simulations, vol. 23, pp. 564-574, 2014.

[5] H. Gao, L. H. Oakley, I. A. Konstantinov, S. G. Arturo, and L. J. Broadbelt, "Acceleration of Kinetic Monte Carlo Method for the Simulation of Free Radical Copolymerization through Scaling," Industrial & Engineering Chemistry Research, vol. 54, pp. 11975-11985, 2015.