2.1.6. Tacticity and Sequence: Advanced Control 4967 2.2. Transition Metal Catalysts 4967 2.2.1. Overviews of Catalysts 4967 2.2.2. Ruthenium 4967 2.2.3. Copper 4971 2.2.4. Iron 4971 2.2.5. Nickel 4975 2.2.6. Molybdenum 4975 2.2.7. Manganese 4976 2.2.8. Osmium 4976 2.2.9. Cobalt 4976 2.2.10. Other Metals 4976 2.3. Cocatalysts (Additives) 4977 2.3.1. Overview of Cocatalysts 4977 2.3.2. Reducing Agents 4977 2.3.3. Free Radical Initiators 4977 2.3.4. Metal Alkoxides 4977 2.3.5. Amines 4978 2.3.6. Halogen Source 4978 2.4. Initiators 4978 2.4.1. Overview of Initiators: Scope and Design 4978 2.4.2. Alkyl Halides 4978 2.4.3. Arenesulfonyl Halides 4979 2.4.4. N-Chloro Compounds 4979 2.4.5. Halogen-Free Initiators 4979 2.5. Solvents 4980 2.5.1. Overview of Solvents 4980 2.5.2. Catalyst Solubility and Coordination of Solvent 4981 2.5.3. Environmentally Friendly Solvents 4981 2.5.4. Water 4981 2.5.5. Catalytic Solvents: Catalyst Disproportionation 4981

Transition metal-catalyzed living radical polymerization : toward perfection in catalysis and precision polymer synthesis

http://pubs.acs.org/doi/pdfplus/10.1021/cr500486u

Recent Developments in the Synthesis of Supported Catalysts

Post-polymerization modification is based on the direct polymerization or copolymerization of monomers bearing chemoselective handles that are inert towards the polymerization conditions but can be quantitatively converted in a subsequent step into a broad range of other functional groups. The success of this method is based on the excellent conversions achievable under mild conditions, the excellent functional-group tolerance, and the orthogonality of the post-polymerization modification reactions. This Review surveys different classes of reactive polymer precursors bearing chemoselective handles and discusses issues related to the preparation of these reactive polymers by direct polymerization of appropriately functionalized monomers as well as the post-polymerization modification of these precursors into functional polymers.

Synthesis of functional polymers by post-polymerization modification.

The notion of metal-free catalysts is used to refer to carbon materials modified with nonmetallic elements. However, some claimed metal-free catalysts are prepared using metal-containing precursors. It is highly contested that metal residues in nitrogen-doped carbon (NC) catalysts play a crucial role in the oxygen reduction reaction (ORR). In an attempt to reconcile divergent views, a definition for truly metal-free catalysts is proposed and the differences between NC and M-Nx /C catalysts are discussed. Metal impurities at levels usually undetectable by techniques such as XPS, XRD, and EDX significantly promote the ORR. Poisoning tests to mask the metal ions reveal the involvement of metal residues as active sites or as modifiers of the electronic structure of the active sites in NC. The unique merits of both M-Nx /C and NC catalysts are discussed to inspire the development of more advanced nonprecious-metal catalysts for the ORR.

On the Role of Metals in Nitrogen-Doped Carbon Electrocatalysts for Oxygen Reduction.

One of the critical issues in the industrial development of fuel cells (e.g., proton exchange membrane fuel cells, direct methanol fuel cells and biofuel cells) is the high cost, serious intermediate tolerance, anode crossover, sluggish kinetics, and poor stability of the platinum (Pt) as the preferred electrocatalysts for the oxygen reduction reaction (ORR) at the cathode. The development of novel noble-metal-free electrocatalysts with low cost, high activity and practical durability for ORR has been considered as one of the most active and competitive fields in chemistry and materials science. In this critical review, we will summarize recent advances on engineering advanced carbon nanomaterials with different dimensions for the rational design and synthesis of noble-metal-free oxygen reduction electrocatalysts including heteroatom-doped carbon nanomaterials, transition metal-based nanoparticle (NP)-carbon nanomaterial composites and especially the stable iron carbide (Fe3C)-based NP-carbon nanomaterial composites. Introducing advanced carbon nanomaterials with high specific surface area and stable structure into the noble-metal-free ORR field has not only led to a maximized electrocatalyst surface area for the electron transfer but also resulted in enhanced electrocatalyst stability for long-term operation. Therefore, the rational design and synthesis of noble-metal-free electrocatalysts based on heteroatoms, transition metal-based NPs and Fe3C-based NP functionalized carbon nanomaterials are of special relevance for their ORR applications, and represents a rapidly growing branch of research. The demonstrated examples in this review will open new directions on designing and optimizing advanced carbon nanomaterials for the development of extremely active and durable earth-abundant cathodic catalysts for fuel cell applications.

Towards high-efficiency nanoelectrocatalysts for oxygen reduction through engineering advanced carbon nanomaterials

Functional spontaneous gradient copolymers of allyl methacrylate (A) and butyl acrylate (B) were synthesized via atom transfer radical polymerization. The copolymerization reactions were carried out in toluene solutions at 100 °C with methyl 2-bromopropionate as the initiator and copper bromide with N,N,N',N",N"-pentamethyldiethylenetriamine as the catalyst system. Different aspects of the statistical reaction copolymerizations, such as the kinetic behavior, crosslinking density, and gel fraction, were studied. The gel data were compared with Flory's gelation theory, and the sol fractions of the synthesized copolymers were characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. The copolymer composition, demonstrating the gradient character of the copolymers, and the microstructure were analyzed. The experimental data agreed well with data calculated with the Mayo-Lewis terminal model and Bernoullian statistics, with monomer reactivity ratios of 2.58 ± 0.37 and 0.51 ± 0.05 for A and B, respectively, an isotacticity parameter for A of 0.24, and a coisotacticity parameter of 0.33.

Synthesis and characterization of functional gradient copolymers of allyl methacrylate and butyl acrylate

Preparation of poly(tert-butyl acrylate-g-styrene) as precursors of amphiphilic graft copolymers. 1. Kinetic study and thermal properties

Free-radical copolymerization of butyl acrylate with methyl methacrylate was carried out at 50°C in a 3 mol/L benzonitrile solution. Differences between the apparent reactivity ratios determined in this work with those previously reported in bulk, toluene and benzene indicate noticeable solvent effects. This fact can be explained through different models, but independent of the chemistry of the system, to obtain the same copolymer composition in bulk or in solution, the monomer feed that should be used is determined by solvent polarity.

Solvent effects on the free-radical copolymerization of butyl acrylate with methyl methacrylate

Atom transfer radical copolymerization of glycidyl methacrylate and allyl methacrylate, two functional monomers

The kinetics of the atom-transfer radical polymerization (ATRP) of dimethyl itaconate (DMI) are discussed. DMI polymerizations were carried out using a CaX/2.2'-bipyridine catalytic system (X = Cl. Br) and a variety of initiators. The polymerizations exhibited a lincar dependence of monomer consumption versus time, up to approximately 50% conversion. A linear increase of munber average molecular weight (M n ) versus monomer conversion was observed. The close correlation of the theoretical molecular weight (M o,th ) with that determined from size exclusion chromatography (M n,SEC ) indicates that these systems have an efficient initiator, and that the number of active chains remains constant during the polymerization. Thermal properties of the polymers synthesized were evaluated and compared to those prepared by conventional free radical polymerization.

José Luis de la Fuente

Papers

Synthesis and characterization of functional gradient copolymers of allyl methacrylate and butyl acrylate

Preparation of poly(tert-butyl acrylate-g-styrene) as precursors of amphiphilic graft copolymers. 1. Kinetic study and thermal properties

Solvent effects on the free-radical copolymerization of butyl acrylate with methyl methacrylate

Atom transfer radical copolymerization of glycidyl methacrylate and allyl methacrylate, two functional monomers

Atom‐Transfer Radical Polymerization of Dimethyl Itaconate