Well-defined linear and star-shaped block copolymers were synthesized using halogenated ATRP macroinitiator via a simultaneous reverse and normal initiation (SR&NI) ATRP process in both bulk and stable aqueous miniemulsion. The miniemulsion was carried out with ∼20% solid (based on 100% conversion), 0.58 wt % nonionic surfactant, Brij 98 (based on water), and 3.6 wt % hexadecane (based on monomer). For example, Br-terminated 3-arm poly(methyl acrylate) (M n = 9200 g/mol; M w/M n = 1.08) was extended with styrene to form star-shaped block copolymer, poly(methyl acrylate)-b-polystyrene, with M n = 24 700 g/mol and M w/M n = 1.41 in bulk condition (yield = 72%) and M n = 22 100 g/mol and M w/M n = 1.37 in miniemulsion (yield = 72%). This newly developed ATRP process requires a significantly reduced amount of highly active ATRP catalyst complex in its oxidatively stable high oxidation state (e.g., CuIIBr2/ligand), while the predominant initiating species was a normal halogen-containing macroinitiator. The compositional analysis of the resulting block copolymer using 2-dimensional chromatography indicated that the final product was essentially composed of block copolymers formed by chain extension of the halogenated macroinitiator via a normal ATRP mechanism. However, the presence of low amounts of linear homopolymers generated by AIBN-initiated species via a reverse ATRP mechanism was also detected.

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Segmented terpolymers, poly(alkyl methacrylate)‐g‐poly(D‐lactide)/poly(dimethylsiloxane) (PLA/PDMS), were prepared with a combination of the “grafting through” technique (macromonomer method) and controlled/living radical polymerization (atom transfer radical polymerization or reversible addition–fragmentation transfer polymerization). Two synthetic pathways were used. The first was a single‐step approach in which a low‐molecular‐weight methacrylate monomer (methyl methacrylate or butyl methacrylate) was copolymerized with a PLA macromonomer and a PDMS macromonomer. The second strategy was a two‐step approach in which a graft copolymer containing one macromonomer was chain‐extended by a copolymerization of the second macromonomer and the low‐molecular‐weight methacrylate. The kinetics of both synthetic approaches were investigated, showing that the polymerizations exhibited a controlled/living behavior. Furthermore, the molecular structure of the terpolymers (composition, molecular weight distribution, and microstructure) was investigated by two‐dimensional liquid chromatography. Well‐defined terpolymers with controlled branch distribution, composition (Fw,PMMA/Fw,PLA/Fw,PDMS ∼ 50/30/20) molecular weight (Mn ∼ 50,000 g · mol−1), and a narrow molecular weight distribution (Mw/Mn ∼ 1.3) were prepared via both pathways. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1939–1952, 2004

A Nafion-Graphene (Nafion-G) nanocomposite solution in combination with an in situ plated mercury film electrode was used as a highly sensitive electrochemical platform for the determination of Zn2+, Cd2+, Pb2+ and Cu2+ in 0.1 M acetate buffer (pH 4.6) by square-wave anodic stripping voltammetry (SWASV). Various operational parameters such as deposition potential, deposition time and electrode rotation speed were optimized. The Nafion-G nanocomposite sensing platform exhibited improved sensitivity for metal ion detection, in addition to well defined, reproducible and sharp stripping signals. The linear calibration curves ranged from 1 μg L−1 to 7 μg L−1 for individual analysis. The detection limits (3σ blank/slope) obtained were 0.07 μg L−1 for Pb2+, Zn2+ and Cu2+ and 0.08 μg L−1 for Cd2+ at a deposition time of 120 s. For practical applications recovery studies was done by spiking test samples with known concentrations and comparing the results with inductively coupled plasma mass spectrometry (ICP-MS) analyses. This was followed by real sample analysis.

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