Graeme Moad

RAFT Copolymerization and Its Application to the Synthesis of Novel Dispersants—Intercalants—Exfoliants for Polymer—Clay Nanocomposites: Some Interesting Results from RAFT (Co)polymerization

This paper will discuss aspects of (co)polymerization of acrylates with reversible addition-fragmentation chain transfer (RAFT). An explanation for bimodal molecular weight distributions observed when making high molecular weight acrylic polymers with narrow molecular weight distributions (M. /M≤1.1) at high conversion involves copolymerization of the macromonomer formed by backbiting-β-scission. Evidence for this mechanism is provided. RAFT copolymerization is illustrated by the synthesis of novel copolymer intercalants/ exfoliants/dispersants for unmodified layered silicates (sodium montmorillonite) in polypropylene (PP) nanocomposites. Block and gradient copolymers were prepared based on a long chain acrylate (e.g. octadecyl acrylate, ODA) and various polar comonomers (e.g. acrylic acid, dimethylaminoethyl acrylate, maleic anhydride, methacrylic acid, N-vinyl pyrrolidone).

CHAPTER 6:Fundamentals of RAFT Polymerization

This chapter sets out to describe the fundamental aspects of radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization). Following a description of the mechanism we describe aspects of the kinetics of RAFT polymerization, how to select a RAFT agent to achieve optimal control over polymer molecular weight, composition and architecture, and how to avoid side reactions which might lead to retardation or inhibition.

Chapter 1:The History of Nitroxide-mediated Polymerization

This chapter traces the early history of nitroxide-mediated polymerization (NMP) during the first ∼15 years. It begins with a short prehistory of observations, made during studies on defining initiation mechanisms using nitroxide radical trapping that can be seen to have inspired the initial experiments. The main part of the chapter is devoted to an account of the discovery of NMP in the early 1980s and research carried out in the period through to 1993, which saw most aspects of the polymerization mechanism defined and the process exploited at CSIRO mainly in the synthesis of acrylic block copolymers. We also provide a brief summary of developments in both the patent and open literature during the period 1993–2000 when the process came to the attention of the wider polymer community mainly for the controlled radical polymerization of styrenics. The end of this period saw the discovery of nitroxides such as SG1 and TIPNO, which provided improved utility and versatility to NMP.