Atom Transfer Radical Polymerization of Methyl Methacrylate Using Telechelic Tribromo Terminated Polyurethane Macroinitiator

Abstract

Novel telechelic tribromo terminated polyurethane (Br3-PU-Br3) was used as a macroinitiator in atom transfer radical polymerization (ATRP) of methyl methacrylate using CuBr as a catalyst and NN,N',N”,N”-pentamethyldiethylenetriamine (PMDETA) as a ligand. During the course of polymerization, poly(methyl methacrylate)-b-polyurethane-b-poly(methyl methacrylate) (PMMA-b-PU-b-PMMA) tri-block copolymers were formed. The resulting tri-block copolymers were characterized by gel permeation chromatography (GPC) and 1H nuclear magnetic resonance (NMR) spectroscopy. Molecular weight of the tri-block copolymers increases with increasing conversion. This result shows Br3-PU-Br3/CuBr/PMDETA initiating system polymerized methyl methacrylate through ATRP mechanism. NMR spectroscopy results revealed that apart from bromine atom transfer from Br3-PU-Br3 to PMDETA-CuBr complex, bromine atom transfer from the initially formed tri-block copolymer to PMDETA-CuBr complex also takes place, and, as a result, double bond terminated copolymer formed. Mole ratio of polyurethane and poly(methyl methacrylate) present in the PMMA-b-PU-b-PMMA tri-block copolymers was calculated using 1H-NMR spectroscopy and it was found to be comparable with the mole ratio calculated through GPC results. Differential scanning calorimetric results confirmed the presence of two different phases in the tri-block copolymers.