RAFT Polymerization Kinetics of a-Methylbenzyl Methacryalte by Dilatometry
- Guillermo Soriano
- Judith Percino
- Víctor Chapela
- Margarita Cerón
- María Castro
AbstractIn this work is present a comparative study of the reversible addition–fragmentation chain transfer and free radical polymerizations of ?-methylbenzyl methacrylate (a-MBM) in solution at 70 °C using 1-phenylehtyldithiobenzoate (1-PEDB) as RAFT agent and AIBN as thermal initiator. Reactions were monitored by dilatometry, which is a robust and economical technique to follow kinetic polymerization. Free radical polymerizations were carried out at initial monomer concentration [a-MBM]0 of 0.2, 0.5, 0.7 and 1.0 M at fixed [AIBN]0 = 1 x 10-3 M and initial initiator concentration of 2, 5, 8 and 10 x 10-3 M at fixed [a-MBM]0 = 0.5 M. For the RAFT polymerizations the [1-PEDB]0 was 4 x 10-3 M using the same reaction conditions that in the free radical polymerizations. In RAFT polymerizations it was found that conversion profiles were lower than in free radical polymerization. Plots of conversion vs time indicated that the polymerizations followed first order kinetics in the range of [a-MBM]0 evaluated. However, only at low [AIBN]0, i.e. 2 and 5 x 10-3 M, kinetics fitted adequately in the reaction time tested. 1H NMR, IR, and UV-Vis spectrophotometric studies confirmed the presence of thiocarbonylthio moieties (-SCS-) in the polymer chains. Molecular weight data for the set of experiments carried out by free radical polymerization decreased when the monomer or the initiator concentration increased. The molecular weight distributions (MWDs) corresponding to the polymers obtained in the RAFT polymerizations were moderately narrow with polydispersities (D) between 1.12 and 1.59.
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