The initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) were investigated in microemulsion under light irradiation with ethyl 2-bromoisbutyrate (EBiB) as an ATRP initiator, ferric chloride hexahydrate (FeCl 3 ·6H 2 O) as a catalyst, N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA) as a ligand, and azobisisobutyronitrile (AIBN) as an initiator and reducing agent. The linear dependence of ln([M] 0 /[M]) on polymerization time was observed, indicating that the polymerization was living polymerization. Furthermore, the number-average molecular weights (Mn), gel permeation chromatography (GPC) and molecular weight distributions (MWD) of the PMMA obtained from GPC were controlled. The product was characterized by 1 H nuclear magnetic resonance (NMR) and GPC. The living features were verified by chain-extended with MMA with the obtained PMMA as macroinitiator.
Block copolymer nano-assemblies were synthesized via initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) dispersion polymerization employing the CuBr2/tris(2-pyridylmethyl)amine catalyst in an alcoholic solvent at a relatively low temperature of 45 °C. The typical poly(ethylene glycol)-block-polystyrene (PEG-b-PS) nano-assemblies synthesized via ICAR ATRP dispersion polymerization are compared with those synthesized via RAFT dispersion polymerization under other similar conditions. It is found that the PEG45-b-PS nano-assemblies, e.g., including lamellas, vesicles and vesicular clusters, synthesized via ICAR ATRP dispersion polymerization have very complicated morphologies, which are different from those synthesized via RAFT dispersion polymerization. The reasons leading to the differences are investigated, and it is conclusively supposed that the high Đ of the synthesized BCPs and the salt of the copper catalyst used in ICAR ATRP dispersion polymerization should be involved. This low temperature initiated ICAR ATRP dispersion polymerization is believed to be a valid method to prepare block copolymer nano-assemblies through polymerization-induced self-assembly.
Diblock copolymer nano-assemblies of poly(2-hydroxypropyl methacrylate-b-benzyl methacrylate) (PHPMA-b-PBzMA) were synthesized by initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) using the CuIIBr2/tris(pyridin-2-ylmethyl)-amine (TPMA) complex as a catalyst under dispersion conditions and were compared with those obtained by RAFT dispersion polymerization. It is found that these two kinds of polymerizations afford good control, as indicated by the linearly increasing molecular weight with monomer conversion and the narrow molecular weight distribution, whereas the ICAR ATRP runs a little faster than RAFT. In the two cases of dispersion polymerization, the morphologies of the PHPMA-b-PBzMA nano-assemblies are similar to each other and change from spheres to wormlike aggregates with block extension, whereas the size of the nano-assemblies by ICAR ATRP is usually larger than those obtained by RAFT. The degree of polymerization (DP) of the poly(2-hydroxypropyl methacrylate) and poly(benzyl methacrylate) blocks affecting the size and/or morphology of the PHPMA-b-PBzMA nano-assemblies is investigated, and the reason for the larger size of the PHPMA-b-PBzMA nano-assemblies by ICAR ATRP is discussed.
Initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of acrylonitrile was first conducted at various ambient temperatures (30–45 °C). The key to success is ascribed to the usage of an appropriate low temperature radical initiator (2,2′-azobis(2,4-dimethylvaleronitrile)) and a high reactivity catalytic system (CuBr 2 /Me 6 TREN). The molar ratio of Cu catalyst to AN as low as 1:20000 was used to prepare well-defined polyacrylonitrile with controlled molecular weight and a narrow polydispersity index range of 1.08–1.30, while the monomer conversion was up to ca . 98%. The apparent activation energy of the polymerization was calculated to be 128.45 kJ/mol, suggesting that the polymerization strongly depended on reaction temperature. The very high chain-end functionality of the resultant polymer was confirmed by 1 H-NMR and GPC analyses as well as chain extension reaction.
Multi-functionalized magnetic graphene was prepared by surface-initiated initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) mediated by polydopamine chemistry . The obtained multi-functionalized magnetic graphene was used as an adsorbent for application in adsorption and speciation of arsenic. Adsorption kinetics and isotherms of arsenic were investigated by batch adsorption experiments. The adsorbent displayed simultaneous or selective removal ability for As(III) and As(V) within different pH ranges. The adsorption of both As(III) and As(V) agreed well with the Freundlich isotherm model, and they were effectively adsorbed through chelation and electrostatic interaction, respectively. Moreover, the functionalized magnetic graphene was examined as a column packing material for speciation analysis of arsenic using solid phase extraction technique. As(III) and As(V) could be effectively separated through a sequential elution strategy. An alkaline solution was firstly employed to selectively elute As(V), and then an acidic solution was utilized to elute As(III). The developed adsorbent in the present study was successfully applied to the determination of As(III) and As(V) in natural and environmental water samples with satisfactory results.
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