Diffusion-controlled polymerization

MARTEN AND HAMiELEC Diffusion-Controlled Polymerization Nomenclature... 

Figure 5 Schematic illustration of defect diffusion-controlled polymerization.45 Reprinted with permission from McLeish, T. C. B. Jones, R. G. Holder, S. J. Macromolecules 2002, 35, 548-554. 2002 American Chemical Society.

The main objective of this work is to review previous studies which relate polymerization kinetics of rodlike molecules to molecular dynamics. Relatively few such studies of diffusion controlled polymerization of rodlike molecules are available in literature, in contrast to the case of flexible polymers which has been well studied [7,8 and references therein]. We thus review the former as well as the fundamental principles involved in some detail. 

The above results illustrate the utility of multiparticle Brownian dynamics for the analysis of diffusion controlled polymerizations. The results presented here are, however, qualitative because of the assumption of a two-dimensional system, neglect of polymer-polymer interactions and the infinitely fast kinetics in which every collision results in reaction. While the first two assumptions may be easily relaxed, incorporation of slower reaction kinetics by which only a small fraction of the collisions result in reaction may be computationally difficult. A more computationally efficient scheme may be to use Brownian dynamics to extract the rate constants as a function of polymer difflisivities, and to incorporate these in population balance models to predict the molecular weight distribution [48-50]. We discuss such a Brownian dynamics method in the next section. 

J. Srinivasalu Gupta, Diffusion controlled polymerization of rodlike molecules, Ph.D. thesis, Indian Institute of Technology, Bombay, 1997. 

Achillas, D.S. (2007) A review of modeling of diffusion controlled polymerization reactions. Macromol. Theory Simul., 16, 319-347. 

Marten F., Hamielec A. High Conversion Diffusion-Controlled Polymerization-, Washington, DC, 1979, 104, p. 43. 

Stickler, M. Panke, D. Hamielec, A.E. (1984) Polymerization of methyl methacrylate up to high degrees of conversion Experimental investigation of the diffusion-controlled polymerization. Journal of Polymer Science Part A Polymer Chemistry Edition, 22, 2243-2253. 

The actual concentration of monomer in the polymer particles (gels) in a diffusion controlled polymerization (at subsaturation pressure and at low agitation speed) equals the equilibrium value given by the value P/Po [133]. The apparent P/Pq values, as well as the corresponding concentrations of monomer in the polymer gel are related to different agitation speeds. For example, with increasing the agitation speed from 500 to 1500 rmp, the monomer concentration increases from 6.1 to 25 g VC/100 g PVC [134]. 

Stickler, M., D. Panke, and A. E. Hamielec, Polymerization of Methyl Methacrylate up to High Degrees of Conversion Experimental Investigation of the Diffusion-Controlled Polymerization, J. Polym. Sci. Polym. Chem. Ed., 22, 2243-2253, 1984. 

---