The “Living” Feature of the ATRP Macroinitiators in Different Catalytic Systems

Abstract

Atom transfer radical polymerization (ATRP) has achieved widespread use in living polymerization. However, until now there has been little report that macroinitiators initiate polymerization in different catalytic systems. The preparation of bromine-terminated polymethyl methacrylate (PMMA-Br) and chlorine-terminated PMMA (PMMA-Cl) were carried out via reverse atom transfer radical polymerization (RATRP). The PMMA with halogen termination and narrow polydispersity (Mn = 12,000–15,000 g/mol, Mw/Mn = 1.1–1.2) were used as macroinitiators. The block copolymer of polymethyl methacrylate and polyacrylonitrile (PMMA-b-PAN) was prepared in different catalytic systems through normal ATRP. The analyses of the 1H NMR showed that the PMMA prepared by RATRP were end-functionalized by halogen atoms, demonstrated the activities of the PMMA macroinitiators. The molecular weight and polydispersity index (PDI) of the polymers were analyzed using gel permeation chromatography (GPC). The results indicated that the block polymers that the molecular weight of the block copolymer after chain extension has increased significantly and the molecular weight distribution is narrow (Mn = 17,000–25,000 g/mol, Mw/Mn = 1.1–1.3). The kinetics of these polymerization processes were studied as a function of monomers to the macroinitiator molar ratio. It was found that the polymerizations in different catalytic systems coincidence first-order kinetics with respect to monomers. In this paper, we reported that the chain extension in different catalytic systems is practicable. The PMMA-Cl and PMMA-Br were obtained in initiating systems of AIBN/FeCl3·6H2O/triphenylphosphine (PPh3) and AIBN/CuBr2/PMDETA, respectively. As the macroinitiators, the PMMA-Cl and PMMA-Br initiate the polymerization in FeCl2/PPh3 and CuBr/PMDETA catalytic systems, respectively. The molecular weight and PDI of the polymers were analyzed using GPC.