Abstract
In 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.
Highlights
The main advantages of free-radical chemistry are the undemanding conditions required for polymerization and the large number of monomers that can be polymerized
We extended our researches at the CRP kinetics studies of such functional monomers (Yáñez-Martínez et al, 2011), in this sense it was found that the nature of the type of monomer in the atom transfer radical polymerization (ATRP) system determined if the polymerization proceed; i.e. it was found that ethylbromopropionate (EBIB) could not initiate the polymerization of N-(S)-α-methylbenzyl methacryloylamine
In this paper we study the reversible addition–fragmentation chain transfer (RAFT) polymerization kinetics of the raceminc α-methylbenzyl methacrylate (α-MBM), under different reaction conditions using 1-phenylethyl dithiobenzoate (1-PEDB), which is an extensively used RAFT agent (Chong et al, 2003)
Summary
The main advantages of free-radical chemistry are the undemanding conditions required for polymerization and the large number of monomers that can be polymerized. One of the main problems encountered in the RAFT polymerization of methacrylates is the selection of RAFT agents suitable for the efficient controlled synthesis of polymers or appropriate reaction conditions (Chiefari et al, 2003; Barner-Kowollik et al, 2001; Zhu et al, 2004a). Well defined poly(α-methylbenzyl methacrylate) macroinitiators were prepared when EBIB and methylchloropropionate (MCP) were used as initiators, such ATRP initiators contain an ester or an amide group (Percino et al, 2011). Recently it was reported the RAFT polymerization of N-(S)-(-)-α-MBMA using typical RAFT agents (Soriano-Moro et al, 2011). In this paper we study the RAFT polymerization kinetics of the raceminc α-methylbenzyl methacrylate (α-MBM), under different reaction conditions using 1-phenylethyl dithiobenzoate (1-PEDB), which is an extensively used RAFT agent (Chong et al, 2003)
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