Polymer chain extension in semibatch emulsion polymerization with RAFT-based transfer agent: The influence of reaction conditions on polymerization rate and product properties

• Published in: Journal of applied polymer science Vol. 114; no. 4; pp. 2356 - 2372
• Main Authors: Altarawneh, Ibrahem S, Gomes, Vincent G, Srour, Mourtada H
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.11.2009; Wiley
• Subjects: Applied sciences; Computer simulation; Conversion; Exact sciences and technology; Feed rate; Manganese; mathematical model; Mathematical models; molecular weight distribution; Monomers; Organic polymers; particle size distribution; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; RAFT; Rafts; secondary nucleation styrene; semi-batch emulsion polymerization; xanthate; Molecular weight distribution; Organic dithiocarbamate; xanthate; Experimental study; Property processing relationship; Modeling; Latex; semi-batch emulsion polymerization; Kinetic model; Particle size distribution; Free radical polymerization; Chain transfer; secondary nucleation styrene; Emulsion polymerization; mathematical model; Numerical simulation; Styrene polymer; Kinetics; RAFT
• ISSN: 0021-8995; 1097-4628; 1097-4628
• DOI: 10.1002/app.30752

A mathematical model was developed for batch and semiemulsion polymerizations of styrene in the presence of a xanthate-based RAFT agent. Zero-one kinetics was employed along with population balance equations to predict monomer conversion, molecular weight (MWD), and particle size (PSD) distributions in the presence of xanthate-based RAFT agents. The effects of the transfer agent (AR), surfactant, initiator, and temperature were investigated. Monomer conversion, MWD, and PSD were found to be strongly affected by monomer feed rate. The polymerization rate (Rp), number average molecular weight (Mn) and particle size (r) decreased with increasing AR. With increases in surfactant and initiator concentrations Rp increased, whereas with increase in temperature Mn decreased, Rp increased and r increased. In semibatch mode, Mn and r increased with increase in monomer flow rate. By feeding the RAFT agent along with the monomer (FM/FAR = NMo/NARo = 100), Mn attained a constant value proportional to monomer/RAFT molar ratio. The observed retardation in polymerization and growth rates is due to the exit and re-entry of small radicals. Thus, chain extension was successfully achieved in semibatch mode. The simulations compared well with our experimental data, and the model was able to accurately predict monomer conversion, Mn, MWD, and PSD of polymer products. Our simulations and experimental results show that monomer feed rate is suitable for controlling the PSD, and the initial concentration and the feed rate of AR for controlling the MWD and PSD.