Mechanistic Aspects of Sterically Stabilized Controlled Radical Inverse Miniemulsion Polymerization

Abstract

The kinetics of RAFT inverse miniemulsion polymerization of acrylamide are presented. The polymerizations exhibit typical behavior of controlled polymerizations under conditions where the hydrolytic degradation of the RAFT agent is less favorable. The effects of different reaction parameters such as temperature, initiator concentration, pH of the aqueous phase, RAFT agent, and surfactant concentration on RAFT inverse miniemulsion polymerization are presented. The particle nucleation process in the inverse miniemulsion polymerizations is evaluated by the use of radical scavengers. The presence of RAFT agent was found to have a significant impact on the particle nucleation process. The fate of desorbed monomeric radicals in inverse miniemulsion polymerizations is evaluated by the comparison of the rates of propagation, re-entry, and termination. One of the potential reasons for the induction time observed in the RAFT inverse miniemulsion polymerizations is suggested to be associated with desorption of monomeric and oligomeric radicals from the particles to the continuous oil phase.

Monitoramento in Situ, Em Tempo Real Da Polimerizacao Em Miniemulsao De Acrilamida Utilizando a Espectroscopia Nir.

“…Though, initial induction times are usually not desired, but the ability to predict correctly the end of the induction time is a desired feature of process monitoring. After this initial induction time, reaction rate was very high due to the high propagation coefficient value of acrylamide, kp = 4.3 x10 4 L.mol -1 s -1 at 60 o C (Qi, 2009) until a limiting conversion between 70 and 80%, depending on the formulation, was reached.…”

“…Hydrophilic polymers have numerous applications, as flocculants, adhesives and viscosity control agent for petroleum, chemicals for the paper industry and mining processes, that represent a market that drives about a billion dollars each year (Ullmann's, 2000 andQi et al, 2009). …”

Acrylamide inverse miniemulsion polymerization: in situ, real-time monitoring using nir spectroscopy

“…On the contrary, the ability to predict correctly the end of the induction period is a desired feature of process monitoring. After this initial induction period, reaction rate was very high due to the high propagation coefficient value of acrylamide, kp = 4.3 x10 4 L.mol -1 s -1 at 60 °C (Qi, 2009) until a limiting conversion between 70 and 80%, depending on the formulation, was reached.…”

“…Hydrophilic polymers have numerous applications, as flocculants, adhesives and viscosity control agent for petroleum, chemicals for the paper industry and mining processes, that represent a market that amounts to about a billion dollars each year (Ullmann's, 2000 andQi et al, 2009). Polyacrylamide is one of those hydrophilic polymers and considerable research has been done to improve its viscosity building capacity by increasing its molecular weight (Hunkeler, 1990) and modifying the polymer chain with a few hydrophobic moieties to create intermolecular hydrophobic association (Feng et al, 2005).…”

Polimerização RAFT em Miniemulsão

“…A Tabela 1 apresenta os estudos publicados até a presente data sobre a produção de polímeros que utilizaram a técnica RAFT em miniemulsão. Conforme revisado, a técnica de polimerização RAFT em miniemulsão já foi adaptada para os principais tipos de monômeros comerciais (como, por exemplo, estireno [28,34,35, , metacrilato de metila [35,54,68,[74][75][76][77][78][79][80] ), sistemas inversos [23,52,[81][82][83][84][85][86] e sistemas contínuos de polimerização [87][88][89] ). 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).…”