Modeling the molecular weight distribution of block copolymer formation in a reversible addition-fragmentation chain transfer mediated living radical polymerization

2005 ◽  
Vol 43 (22) ◽  
pp. 5643-5651 ◽  
Author(s):  
Michael J. Monteiro
Keyword(s):  
Molecular Weight ◽  
Block Copolymer ◽  
Radical Polymerization ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Chain Transfer ◽  
Living Radical Polymerization ◽  
Reversible Addition

Modelling the Complete Molecular Weight Distribution in Chain Growth Polymerizations

2016 ◽  
Vol 1819 ◽  
Author(s):  
Ramiro Infante-Martínez ◽  
Enrique Saldívar-Guerra ◽  
Odilia Pérez-Camacho ◽  
Maricela García-Zamora ◽  
Víctor Comparán-Padilla
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Radical Polymerization ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Chain Transfer ◽  
Free Radical Polymerization ◽  
Experimental Program ◽  
Chain Growth ◽  
Coordination Polymerization

ABSTRACTThis work shows the development of several models for chain-growth polymerizations that admit the direct calculation of the complete molecular weight distribution of the polymer. The direct and complete calculation implies that no statistical mean values are employed as in the moments method neither numerical approximations like in the minimum-squared based methods. The free radical polymerization of ethylene (LDPE) and the coordination via metallocenes polymerization of ethylene (HDPE) are taken as examples for analysis.In the free radical polymerization case, the conventional scheme for chain-growth polymerization is adopted, with steps for initiation, propagation, chain transfer to small species and the additional step of chain transfer to dead chains [1]. The kinetic parameter are obtained from the open literature. Two kind of reactors were modelled: batch and continuous stirred tank reactor. For this last case, a simulation strategy was considered in which the run started from an initial known population of dead chains. Results show that typical non-linear polymerization profiles for the molecular weight distribution are obtained. For the coordination polymerization of ethylene via metalocenes, the standard coordination model was employed [2]. A two-site catalyst was considered and kinetic parameters reported in the open literature were used. For this study an experimental program in a lab-scale reactor was undertaken in order to obtain modelling data [3]. Results show that the standard model adequately reproduces the experimental data in the kinetic and molecular attributes of the polymer.

The Application of Supercomputers in Modeling Chemical Reaction Kinetics: Kinetic Simulation of 'Quasi-Living' Radical Polymerization

1990 ◽  
Vol 43 (7) ◽  
pp. 1215 ◽  
Author(s):  
CHJ Johnson ◽  
G Moad ◽  
DH Solomon ◽  
TH Spurling ◽  
DJ Vearing
Keyword(s):  
Molecular Weight ◽  
Differential Equations ◽  
Radical Polymerization ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Euler Method ◽  
Living Radical Polymerization ◽  
Kinetic Simulation ◽  
Stiff Systems ◽  
Chemical Reaction Kinetics

A computer program has been written which employs an implicit Euler method to solve directly the complete set of coupled differential equations which result from an analysis of polymerization kinetics. The program was written to make full use of the speed and power of modern supercomputers, and is suited to the solution of very large stiff systems of differential equations. The benefit of treating each propagation step as a discrete reaction is that information on the evolution of the molecular weight distribution is obtained directly without the need to make perhaps unjustified assumptions such as the steady-state approximation. For illustrative purposes, the method has been applied in the kinetic simulation of 'quasi-living' radical polymerization to assess the effect of experimental variables on the molecular weight, molecular weight distribution, and rate of polymerization. The calculations show that 'quasi-living' radical polymerization can produce polymers with polydispersities approaching those obtained with anionic 'living' polymerizations. Some necessary conditions for the formation of polymers with narrow molecular weight distribution are defined.

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