Stereocontrol of Methyl Methacrylate during Photoinduced Nitroxide-Mediated Polymerization in the Presence of Photosensitive Alkoxyamine

Juahui Su,Yanyan Cui,Maijun Li,Xiaoxuan Liu,Ting Zhang

doi:10.1155/2016/6482050

Abstract

Photosensitive alkoxyamine 2,2,6,6-tetramethyl-1-(1-phenylethoxy)piperidin-4-yl quinoline-2-carboxylate (PE-TEMPO-Q) was synthesized. Photochemical properties of PE-TEMPO-Q were studied to develop photoinduced nitroxide-mediated polymerization of methyl methacrylate (MMA). Rapid and facile polymerization at ambient temperature with PE-TEMPO-Q as an initiator was confirmed to proceed in a controlled mechanism based on the linear growth in molecular weight combined with relative narrow polydispersity index (1.4–1.8) of the resulting polymers. The stereochemistry of obtained polymers was also investigated, and the syndiotacticity slightly increased compared with the typical photopolymerization. Dual-controlled photopolymerization of MMA was achieved in the presence of synthesized alkoxyamine.

Highlights

The design and preparation of well-defined polymers at the molecular level has been one of the major concerns in synthetic polymer chemistry over the past several decades
It has been proved that photosensitive alkoxyamine with a chromophore could be applied to the control/living free radical polymerization according to similar observations from the unimolecular thermal alkoxyamines [22, 23]
We first synthesized a traditional alkoxyamine with hydroxyl group originally developed by Matyjaszewski et al [25], in which the reaction of the alkyl halide in the presence of Cu(0)/CuBr/bpy complex was used as a convenient source of alkyl radicals

Summary

Introduction

The design and preparation of well-defined polymers at the molecular level has been one of the major concerns in synthetic polymer chemistry over the past several decades. Controlled/living radical polymerization (CRP) methods, which mainly include nitroxide-mediated polymerization (NMP) [1], atom transfer radical polymerization (ATRP) [2], and reversible addition-fragmentation chain transfer (RAFT) [3], have been developed primarily to prepare polymers with predetermined molecular weights, low polydispersities, and specific topologies. The stereochemical control is an important issue in developing excellent novel polymer materials because physical and mechanical properties are highly dependent on tacticity. Anionic and coordination polymerizations have been applied to achieve various stereochemical control polymers [4, 5]. Radical polymerization is much less successful in controlling tacticity because of the radical nature of the propagation step such that the planarity of the generated radicals (sp hybridization) offers similar probabilities of meso and racemic addition, resulting in atactic polymers. Several approaches have been established to control tacticity by polymerization under confined media such as the addition of solvents or additive-mediated system, even by polymerizing monomer with inherent stereospecificity [6,7,8]

Methods

Results

Conclusion