Introduction. Controlled radical polymerization 1 (CRP) has been the focus of intense research in recent years. Atom transfer radical polymerization (ATRP), 2 nitroxide-mediated polymerization (NMP), 3 and more recently, reversible addition-fragmentation chain transfer polymerization (RAFT) 4 have allowed for the synthesis of (co)polymers with designated molecular weights and narrow molecular weight distributions.Considering the advantages of precisely controlled structures and the need for environmentally viable technologies, we have recently centered our efforts on conducting CRP in aqueous media. We first reported the synthesis, via RAFT, of homopolymers and block copolymers based on the water-soluble styrenic monomers, sodium 4-styrenesulfonate, sodium 4-styrenecarboxylate, N,N-dimethylvinylbenzylamine, and (ar-vinylbenzyl)trimethylammonium chloride. 5 Subsequently, we reported the first example of CRP of anionic acrylamido monomers in aqueous media. 6 As well as ionic monomers, we are interested in polymerizing nonionic hydrophilic/water-soluble species, such as N,N-dimethylacrylamide (DMA) via RAFT. Herein, we report the CRP of DMA, in aqueous media, utilizing two RAFT CTAs, Table 1. As far as we are aware, this constitutes the first report outlining the CRP of this monomer via RAFT in water.The CRP of DMA, and acrylamido monomers in general, has proven to be challenging using techniques such as ATRP and NMP. Li and Brittain reported the polymerization of DMA by NMP using TEMPO, but the process was shown to be uncontrolled. 7 However, with the development of more universal nitroxides, Benoit et al. demonstrated the ability to (co)polymerize DMA via NMP. 8 Teodorescu and Matyjaszewski reported the ATRP of several (meth)acrylamides. 9 However, the authors concluded that these systems were not "living". This was subsequently confirmed by Rademacher et al. 10 Senoo et al. reported the ATRP synthesis of PDMA, employing the RuCl 2 (PPh 3 ) 3 -based initiating system, although resulting polydispersities were typically >1.60. 11 With the discovery of RAFT, a wider range of monomers are now amenable to CRP. Significantly, the CRP of DMA 12 and N-isopropylacrylamide, 13 via RAFT, in organic media have already been demonstrated.In the work reported here, DMA homopolymers were synthesized in water via RAFT. Both sodium 4-cyanopentanoic acid dithiobenzoate (CTPNa) and N,N-dimethyl-s-thiobenzoylthiopropionamide (TBP) were employed as the RAFT chain transfer agents (CTAs). CTPNa was chosen due to its inherent water-solubility

A novel bifunctional acrylamido-based reversible addition-fragmentation chain transfer (RAFT) chain-transfer agent (CTA), N, propionamide] (CTA2), has been synthesized and used for the controlled freeradical polymerization of N,N-dimethylacrylamide (DMA). A comparative study of CTA2 and the monofunctional CTA N,N-dimethyl-s-thiobenzoylthiopropionamide (CTA1) has been conducted. Polymerizations mediated by CTA1 result in poly(N,Ndimethylacrylamide) (PDMA) homopolymers with unimodal molecular weight distributions, whereas CTA2 yields unimodal, bimodal, and trimodal distributions according to the extent of conversion. The multimodal nature of the PDMAs has been attributed to termination events and/or chains initiated by primary radicals. The RAFT polymerization of DMA with CTA2 also results in a prolonged induction period that may be attributed to the higher local concentration of dithioester functionalities early in the polymerization. A series ofand ␣,-dithioester-capped PDMAs have been prepared in organic media and subsequently employed as macro-CTAs for the synthesis of diblock and triblock copolymers in aqueous media with the zwitterionic monomer 3-[2-(N-methylacrylamido)-ethyldimethylammonio] propane sulfonate (MAEDAPS). Additionally, an -dithioester-capped MAEDAPS homopolymer has been used as a macro-CTA for the block polymerization of DMA. To our knowledge, this is the first example of a near-monodisperse, sulfobetaine-containing block copolymer prepared entirely in aqueous media. The diblock and triblock copolymers form aggregates in pure water that can be dissociated by the addition of salt, as determined by 1 H NMR spectroscopy and dynamic light scattering. In pure water, highly uniform, micellelike aggregates with hydrodynamic diameters of 71-93 nm are formed.