Mechanistic Study Of Self-initiated Catalytic Oxidiative Polymerization Of (N,N-dialkylamino)ethyl Methacrylate

As an intrinsically reducing monomer,（N,N-dialkylamino）ethylmethacrylate was reported to be involved in redox initiation in the presence ofproper oxidizing agents. First, Self-initiated oxidative radical polymerizationof DMAEMA catalyzed with CuCl₂/PMDETA were performed in thepreaence of O2. The monomer conversion was determined by GC. The MW,chain structure and thermal transition were characterized by GPC,¹H-NMRspectroscopy and DSC, respectively. The¹H-NMR spectroscopy implied thatthe ODMAEMA contained both a methacryloyl CH₂=and a C-Cl terminus.The CuCl/PMDETA-catalyzed ATRP of MMA using the so-obtainedODMAEMA as the macroinitiator was carried out. The results showed thatthe process proceeded. The¹H-NMR spectra showed that the relative intensityof the-N-CH₃moiety to-OCH₂-decreased remarkably, suggesting that MMAwas also graft-copolymerized to ODMAEMA, which confirmed that theN-CH₃moiety of DMAEMA was oxidized into the N-CH₂· radical by CuCl₂，and that ATRP mechanism partially resulted in the process.Then, oxidative polymerizations of DEAEMA as an intrinsicallyreducing monomer catalyzed by high-oxidation state transition metals（CuX₂/L, FeX₃/L, X=Cl or Br, L=bPy, TMEDA, PMDETA, CuSO₄） weresystematically investigated. The results showed that even in the absence ofany chemical initiators, the high-oxidation state transition metals can steadilycatalyze the free radical polymerization of DEAEMA. The MW of thePDEAMEA increased gradually with the conversion, while it maintained arather broad PDI even from low conversions. The MALLS results showedthat the absolute MW of the PDEAEMA demonstrated an unusualmulti-modal distribution. By comparing the CuSO₄-catalyzed redox-initiationability of lower-MW tertiary amines, it can be concluced that DEAEMAfunctions as an intrinsically reducing monomer under the catalysis ofhigh-oxidation state transition metals, which oxidize the alpha C-H （Cα-H） ofthe amine group of DEAEMA into the Cα· radicals, initiating the conventionalradical polymerization of DEAEMA and giving rise to linear PDEAEMAprimary chains. Subsequently, the linear PDEAEMA chains serve asmacro-initiators with high-oxidation state transition metals and initiate the graft polymerization of DEAEMA, leading to branched PDEAEMA with acertain number of side chains.In order to verify whether the initiatable radicals formed during theCu²⁺-tertiary amine redox process. The AGET-ATRP of MMA was carried outwhich using the linear PDMAEMA as the macro-reducer and CuBr₂/bPy asthe initiator. The results showed that the α-tBBiB was added or not, theprocess proceeded successfully. It confirmed that the the N-CH₃moiety oflinear PDMAEMA was oxidized into the N-CH+2· radical by Cu2. Taking thefact into account that tertiary amines are widely used in ATRP as ligands, it isclear that the Cu^2+tertiary amine redox initiation was significant to a certainextent.