The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

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

“Life is branched” was the motto of a special issue of Macromolecular Chemistry and Physics1 on “Branched Polymers”, indicating that branching is of similar importance in the world of synthetic macromolecules as it is in nature. The significance of branched macromolecules has evolved over the last 30 years from just being considered as a side reaction in polymerization or as a precursor step in the formation of networks. Important to this change in perception of branching was the concept of “polymer architectures”, which formed on new starand graft-branched structures in the 1980s and then in the early 1990s on dendrimers and dendritic polymers. Today, clearly, controlled branching is considered to be a major aspect in the design of macromolecules and functional material. Hyperbranched (hb) polymers are a special type of dendritic polymers and have as a common feature a very high branching density with the potential of branching in each repeating unit. They are usually prepared in a one-pot synthesis, which limits the control on molar mass and branching accuracy and leads to “heterogeneous” products with a distribution in molar mass and branching. This distinguishes hyperbranched polymers from perfectly branched and monodisperse dendrimers. In the last 20 years, both classes of dendritic polymers, dendrimers as well as hb polymers, have attracted major attention because of their interesting properties resulting from the branched architecture as well as the high number of functional groups.2 The challenging synthesis of the dendrimers attracted especially scientists with a strong organic chemistry background and led to beautifully designed macromolecules, which allowed a deeper insight into the effect of branching and functionality. Dendrimers have been considered as perfect “nano-objects” where one can control perfectly size and functionality, which is of high interest in nanotechnology and biomedicine. hb polymers, however, were considered from the beginning as products suitable for larger-scale application in typical polymer fields like coatings and resins, where a perfect structure is sacrificed for an easy and affordable synthetic route. Thus, the first structures that were reported paralleled the chemistry used for linear polymers like typical polycondensation for polyester synthesis. More recently, unconventional synthetic methods have been adopted also for hb polymers and related structures. Presently, a vast variety of highly branched structures have been realized and studied regarding their properties and potential application fields. Excellent reviews appeared covering synthesis strategies, properties, and applications, like the very recent tutorial by Carlmark et al.,3 the comprehensive book on hyperbranched polymers covering extensively synthesis and application * E-mail: voit@ipfdd.de; lederer@ipfdd.de. Chem. Rev. 2009, 109, 5924–5973 5924

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Hyperbranched and highly branched polymer architectures--synthetic strategies and major characterization aspects.

Over the past century, hydrogels have emerged as effective materials for an immense variety of applications. The unique network structure of hydrogels enables very high levels of hydrophilicity and biocompatibility, while at the same time exhibiting the soft physical properties associated with living tissue, making them ideal biomaterials. Stimulus-responsive hydrogels have been especially impactful, allowing for unprecedented levels of control over material properties in response to external cues. This enhanced control has enabled groundbreaking advances in healthcare, allowing for more effective treatment of a vast array of diseases and improved approaches for tissue engineering and wound healing. In this extensive review, we identify and discuss the multitude of response modalities that have been developed, including temperature, pH, chemical, light, electro, and shear-sensitive hydrogels. We discuss the theoretical analysis of hydrogel properties and the mechanisms used to create these responses, highlighting both the pioneering and most recent work in all of these fields. Finally, we review the many current and proposed applications of these hydrogels in medicine and industry.

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Stimulus-responsive hydrogels: Theory, modern advances, and applications

Polystyrene (PS)/poly(ethylene oxide) (PEO) amphiphilic star-block copolymers and dendrimer-like architectures were prepared using a core-first method PS stars were first obtained by atom transfer radical polymerization using three and four functional benzyl halides The chain ends of these star polymers were subsequently modified to generate either the same or twice the number of hydroxyl groups that served to grow the PEO blocks by anionic polymerization of ethylene oxide Well-defined PSn-b-PEOn (n = 3 or 4) stars and PS3-b-PEO6 dendrimer-like copolymers exhibiting a monomodal and narrow molar mass distribution were obtained in this way When spread at the air/water interface, these stars proved to be surface active, forming stable reproducible films Isotherms yielded A0 (theoretical surface area occupied by a film at zero pressure) values, allowing for quantitative comparisons between the stars and linear diblock analogues Both structures demonstrated similar behavior, passing from liquid expanded 

Synthesis and Surface Properties of Amphiphilic Star-Shaped and Dendrimer-like Copolymers Based on Polystyrene Core and Poly(ethylene oxide) Corona

AA‘2-type asymmetric stars and AB2-type miktoarm star polymers were prepared by combination of atom transfer radical polymerization (ATRP) and chemical modification of the termini of ATRP-derived polymers. The first step involved the preparation of ω-bromopolystyrene (PS) chains by ATRP using ethyl 2-bromoisobutyrate as initiator. Styrene was polymerized in bulk at 100 °C in the presence of Cu(I)Br and pentamethyldiethylenetriamine (PMDETA) as catalytic system. Next, the bromo end groups of the resulting PS chains were derivatized into twice as many bromoisobutyrates in order to obtain ω,ω‘-bis(bromo)-PS chains. The last step consisted of growing either two additional PS or two poly(tert-butyl acrylate) (PtBA) blocks by ATRP, following the same polymerization conditions as those mentioned above. This methodology enabled us to synthesize AA‘2 triarm PS stars with asymmetry in the molar mass of their branches and PS(PtBA)2 stars with chemically different PS and PtBA arms. According to the evolution of molar...

Toward an easy access to asymmetric stars and miktoarm stars by atom transfer radical polymerization

The synthesis of dendrimer-like polystyrene (PS) of second and third generations by combination of atom transfer radical polymerization (ATRP) and chain end modifications is reported. Calixarene-based cores were used as initiators for ATRP of styrene yielding star polymers containing precisely 4, 6, or 8 arms. The latter were modified in two steps so as to generate PS stars carrying 8, 12, or 16 terminal bromoisobutyrate groups, respectively. These precursors served as multifunctional macroinitiators for the formation of the second generation of dendrimer-like PS. Reiteration of the aforementioned sequence of reactions allowed to derive dendrimer-like polystyrene of third generation that were constituted of 16, 24, or 32 outer arms, respectively. The chain end modification was monitored by 1H NMR spectroscopy. The dendrimer-like PS were also characterized by size exclusion chromatography equipped with a multiangle laser light scattering detector (SEC/MALLS). The actual polymer architecture and the functio...

Synthesis of Dendrimer-Like Polystyrene by Atom Transfer Radical Polymerization and Investigation of Their Viscosity Behavior

The addition of inorganic nanoparticles to polymers causes changes in the properties and applications of both the nanoparticles and polymers. In this review article the functionalization of nanoparticles, grafting of polymers on nanoparticles, properties, and applications of a number of nanoparticle-polymer composites are discussed. It can be seen that in all these cases attempts have been made to uniformly disperse nanoparticles in polymer matrix for the purpose of gaining stability and processability. This review is limited to the recent developments in the field of metal/metal oxide nanoparticles only. The carbon nanotube functionalized with polymer was seen as a very large area and it is omitted here due to size constraints.

Raju Francis

Papers

Synthesis and Surface Properties of Amphiphilic Star-Shaped and Dendrimer-like Copolymers Based on Polystyrene Core and Poly(ethylene oxide) Corona

Toward an easy access to asymmetric stars and miktoarm stars by atom transfer radical polymerization

Synthesis of Dendrimer-Like Polystyrene by Atom Transfer Radical Polymerization and Investigation of Their Viscosity Behavior

Polymer Grafted Inorganic Nanoparticles, Preparation, Properties, and Applications: A Review

Recycling of Polymers: Methods, Characterization and Applications