Monte Carlo Simulation of Controlled/Living Radical Polymerization in Emulsified Systems

Abstract

A new MC simulation method is proposed for the controlled/living radical polymerization in a dispersed medium, assuming an ideal miniemulsion system. This tool is used to consider the effects of particle size on the polymerization rates and the molecular weight distributions. For NMP, the polymerization kinetics are basically governed by two conflicting factors, (i) the confined space effect that promotes the coupling reaction between a radical and a trapping agent and (ii) the isolation effect of radicals into different particles that suppresses the overall frequency of bimolecular termination. For RAFT polymerization, a significant rate enhancement by reducing the particle size could be observed only for the systems with fast fragmentation of adduct radicals.magnified image

Threshold Particle Diameters in Miniemulsion Reversible-Deactivation Radical Polymerization

“…On the other hand, these two types of models can be discriminated in a straightforward manner by using the miniemulsion polymerization. The IT model leads to show that the polymerization rate increases significantly for D p smaller than ,PXP , while with the SF model the polymerization rate is essentially unchanged with the particle size [9,13,21]. Recently, this simple discrimination method is applied experimentally [22], and concluded that the IT model applies for the dithiobenzoate mediated styrene polymerization.…”

“…On the other hand, L ν,i is the average number of monomeric units added during a single active period, and therefore, given by: (9) where • is the average active radical period in the ith polymerization locus (particle), which is given by:…”

“…Note that the termination rate constant, k t is defined by • , not 2 • . The MC calculation method used in this article is described in [9]. When applying Equations (11) and (12) (11) and (12).…”

“…For SRMP and ATRP, theoretical calculation results have shown that a particle size region may exist in which the polymerization rate is larger than bulk polymerization [6][7][8][9][10][11][12][13][14], which was named the acceleration window [10]. Figure 2 shows a typical example.…”

Polimerização RAFT em Miniemulsão

“…Além dos trabalhos citados na P(AM-co-AA) Inverso [83] P(NIPAM-b-PEO) Inverso [82] a Poliestireno (PSt), poli(metacrilato de metila) (PMMA), poli(buitl metacrilato (PnBMA), poli(hidroxietil metacrilato) (PEHMA), poli(butil acrilato) (PnBA), poli(acetato de vinila) (PVAc), Poliacrilamida (PAM), poli(ácido acrílico), poli(2-dimetilamino (metacrilato de etila)) (PDMAEMA), ácido metacrílico (MAA), acrilato de dodecafluoro heptil (DFHA), acrilamida (AM), ácido acrílico (AA), isopopil acrilamida (NIPAM), poli(óxido de etileno) (PEO). Tabela 1, estudos teóricos sobre a polimerização RAFT em miniemulsão também já foram publicados [90][91][92][93][94][95][96][97] , contribuindo com a melhor compreensão sobre a cinética de polimerização (e outras características) desse sistema.…”