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Nitroxide mediated radical polymarization in emulsion and miniemulsion at low temperatures

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Author(s):
Samara Boaventura de Moraes
Total Authors: 1
Document type: Doctoral Thesis
Institution: Universidade Estadual de Campinas, Faculdade de Engenharia Química
Defense date:
Advisor: Liliane Maria Ferrareso Lona
Abstract

The controlled polymerization is aimed at producing polymers with narrow molar mass distributions and polydispersity close to 1.0. Among the polymerization techniques available, one of the most commonly used is the nitroxide mediated radical polymerization (NMRP), being a versatile technique, effective, easy to apply, low cost. One of the most commonly used nitroxide radicals is 2,2,6,6-tetramethyl-1-piperidinoxyl (TEMPO). The development of this technique in heterogeneous systems, such as emulsion, is a great challenge, since when TEMPO is used, it is necessary high temperatures (~ 120 ºC), but in emulsion the reaction takes place in aqueous medium and the boiling temperature of the water is 100 ºC, ie, it would be necessary to use a pressurized system when using TEMPO. The main purpose of this work is to study the emulsion polymerization system using NMRP and TEMPO at temperatures below 100 ºC by adding sodium bicarbonate to the reaction medium. In order to understand the kinetic effect of sodium bicarbonate on polymerization, besides emulsion polymerization, mass polymerization and miniemulsion were also carried out. Results obtained for mass polymerization through gravimetric analysis, Fourier transform infrared spectroscopy (FTIR), Fourier transform Raman spectroscopy (FT-Raman) and differential scanning calorimetry (DSC) analyzes show no interference of sodium bicarbonate to the reaction medium. In the controlled emulsion polymerization with TEMPO at temperatures below 100 ºC the reaction did not occur. When sodium bicarbonate was added to the reaction medium, it was possible to obtain high conversion rates, indicating a significant effect of sodium bicarbonate on the kinetics of the reaction when this occurs in emulsion. UV-vis analyzes indicate that TEMPO tends to be consumed rapidly in acid medium. In an acid environment, the protonation of the TEMPO molecule with H+ ions occurs. These protonated molecules can react with radicals of the initiator and polymer chain, acting as reaction inhibitor. In neutral medium there is no protonation of TEMPO molecule, which may be an important factor for the emulsion reaction to occur when sodium bicarbonate is added to the reaction medium. In the miniemulsion polymerizations, the conversions obtained were very low at a temperature below 100 ºC, for both polymerization with TEMPO and polymerization controlled with TEMPO and sodium bicarbonate, indicating that the polymerization, in this case, does not occur (AU)

FAPESP's process: 12/21740-0 - Free radical polymerization mediated by nitroxides in emulsion and miniemulsion at low temperatures
Grantee:Samara Boaventura de Moraes
Support type: Scholarships in Brazil - Doctorate