Posocco, Alice (2011) Attivazione di polimerizzazioni radicaliche a trasferimento di atomo: l'effetto del solvente. [Laurea specialistica biennale]
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The solvent effect on the activation process of atom transfer radical polymerisation (ATRP) is investigated for a system composed by ethyl chloroacetate as initiator and copper(I)Me6TREN as catalyst. A set of ten solvents with different properties is considered for this analysis: Acetonitrile, N,N-dimethylformamide, dimethylsulfoxide, acetone, propylen carbonate, anisole, methanol, ethanol, 2-propanol, water. In the first instance the Cu(II)Me6TREN/Cu(I)Me6TREN redox couple is characterized by means of cyclic voltammetry in order to examine the solvent effect on the redox properties of the catalyst. In the second place the role of copper(I)Me6TREN disproportionation is evaluated through the set of solvents by means of rotating disk electrode chronoamperometry. Next, with the same electrochemical technique, the kinetics of the activation reaction between catalyst and ethyl cloroacetate is examined. The results show that the medium affects the standard potential of the catalyst, which in its turn highly influences the polymerization process. In particular, the Lewis basicity of the solvent seems to be the most influenting property, and this could be explained by the the copper(II)Me6TREN having a free coordination site. The disproportionation process is negligible with respect to the activation one. The velocity (kinetic constant) of the latter is affected by the solvent as well as the catalyst potential, but with a different trend. A thermodinamic analysis is carried out to explain this dependence.
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