Kinetic Studies and Monte Carlo Simulations of radical Ter- and Tetrapolymerisations
Advancing the chemical engineering fundamentals
Polymer Science & Engineering - II (T2-12b)
Keywords: radical polymerization, terpolymerization, monte carlo simulation, semi-batch
Radical polymerisation of three and more monomers with different reactivities can lead to polymers with extremely different copolymer compositions during the polymerisation process. A Monte Carlo (MC) simulation method will be presented to describe the copolymer composition dependent on the conversion, the integral and differential copolymer mixture, the comonomer conversions and sequence distributions of the comonomers. The results were verified by experimental investigations of ter- and tetrapolymerisations of donor-, acceptor-, and neutral monomers in batch and semibatch experiments.
For the conversion dependent simulation of these ter- and tetrapolymerisations, the r-values of the corresponding binary systems and the initial molar compositions of the reaction mixture are required. The applied MC simulation processes a defined total number of monomer molecules of ntot=1∙108 that are distributed among the given monomer species according to the initial molar composition of the feed. Every single step in this MC simulation represents the incorporation of one monomer unit into the polymer based upon the effective reaction probabilities for the given reaction conditions. The results of the simulation are tracked at steps of 1% of total monomer conversion and are analyzed in respect to the integral composition of the polymer, composition of the monomer feed mixture and conversion of the given monomers. By comparison with the result of the preceding analysis step, the differential polymer composition is calculated. Moreover, analysis of the sequence of monomer units provides information about the numbers for each sequence length of all involved monomers at every analysis step.
The Monte Carlo simulation procedure is executed by the mcCopolymer program, programmed in C++ with a Tcl-interface, and employing the Mersenne Twister high-level 623-dimensionally equidistributed uniform pseudo-random number generator [1].
Comparison between the experimental results and the MC simulation for radical polymerisations of donor, acceptor and neutral monomers with highly different reactivities, demonstrates the precision of the presented Monte Carlo model for terpolymerisations and tetrapolymerisations. If the r-values of the binary sub-systems are correctly known, copolymer compositions, comonomer compositions and monomer conversions can be described in good agreement with experimental data up to high conversions. The calculated, differential copolymer compositions and sequence distributions lead to a better understanding of the correlations between polymer structure and feed composition for multicomponent polymerisations. Furthermore, these MC simulations are a powerful tool for the development of semi-batch regimes for the synthesis of chemically uniform polymers.
[1] M. Matsumoto, T. Nishimura, ACM Trans Model Comp. Simul. 1998, 8, 3
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 08:45 to 09:05, in session Polymer Science & Engineering - II (T2-12b).
